South Florida's loggerhead (Caretta caretta), green (Chelonia mydas) and leatherback (Dermochelys coriacea) sea turtles hatchling have environmentally determined sex. The in situ nest mean hatchling sex ratios (SR) were highly female-biased : loggerhead F=0.89) and green turtle F=0.81; leatherback's SR was nearly balanced (0.55F). Nest temperatures and SRs differed between leatherbacks and loggerhead and green turtles. The latter two did not differ. The loggerhead response parameters were estimated within biological limitations by both 50-65% of incubation and mean middle 1/3 temperature. The maximum middle 1/3 temperature was the best-fit predictor for green turtles. No best-fit sex ratio-temperature response could be identified for leatherbacks. Clutches incubating under natural conditions can vary greatly in SR ; TRT differences may account for differences among species' sex ratios. / by Micah Marie Rogers. / Thesis (M.S.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

Diversos genes expressos durante a diferenciação das células germinativas atuam no desenvolvimento ovariano. A diferenciação das células somáticas ovarianas depende do número de células germinativas pré-meióticas que migram para a fenda gonadal. A expressão espaço-temporal de genes envolvidos na diferenciação dessas células e a posterior sobrevivência dos oócitos meióticos são de interesse no estudo dos distúrbios do desenvolvimento sexual (DDS) 46,XX. Entre os genes envolvidos nesses processos estão o NANOS3, BMP15 e STRA8. O NANOS3, uma molécula de ligação ao RNA que bloqueia a via apoptótica, assegura a sobrevivência das células germinativas durante sua migração para o interior da gônada. O STRA8 atua no início da meiose das células germinativas na gônada de embriões XX, sendo o primeiro sinal de dimorfismo gonadal. Por outro lado a subseqüente sobrevivência dos oócitos é controlada por fatores de transformação e crescimento como o BMP15, que promove a diferenciação das células da granulosa que por sua vez participam indiretamente da diferenciação dos oócitos e das células da teca. Neste trabalho pesquisamos a presença de mutações inativadoras nos genes NANOS3 e BMP15 em 45 pacientes com disgenesia gonadal (DG) 46,XX (10 casos familiais) e 40 pacientes com amenorréia secundária sem mutação nos genes FSHR e SF1. Também pesquisamos mutações nas regiões promotora proximal e codificadora do gene STRA8 de 45 pacientes com DG 46,XX, 16 pacientes com DDS ovotesticular 46,XX e 5 pacientes com DDS testicular 46,XX todos SRY negativo nos quais foram afastados defeitos moleculares nos genes DAX1, WNT4 e SOX9. No NANOS3 identificamos a mutação p.E120K em homozigose, a primeira associada ao fenótipo de DG 46,XX. Esta mutação missense foi identificada em duas irmãs com DG 46, XX e está localizada no domínio de ligação do tipo dedo de zinco da proteína. A nova mutação não foi identificada em 200 alelos controles pesquisados. No BMP15, uma nova mutação nonsense p.Q115X foi identificada em homozigose em duas irmãs com DG 46XX e em heterozigose em uma paciente com amenorréia secundária não familial. O códon de parada prematuro está localizado na região do pré-peptídeo da proteína. A nova mutação não foi identificada em 200 alelos controles pesquisados. No gene STRA8, um único polimorfismo previamente descrito na literatura (rs7805859) foi identificado na região codificadora e nenhuma alteração na região promotora proximal foi identificada. Em conclusão, identificamos pela primeira vez uma mutação no gene NANOS3 associado á DG 46,XX e confirmamos a participação do BMP15 neste fenótipo. Distúrbios do desenvolvimento gonadal 46, XX podem ser causados por mutações em genes envolvidos tanto na diferenciação quanto manutenção das células germinativas ovarianas. / Several genes expressing during the germ cell differentiation act in ovary development. The differentiation of somatic ovary cells depends of a pool of pre meiotic germ cells migration into the gonad. The space and temporal expression pattern of some genes involved with germ cell differentiation and the subsequently oocyte survival should be investigated in the disorders of sexual development (DSD) 46,XX. Some key genes involved with these processes are: NANOS3, BMP15 and STRA8. The NANOS3, a RNA binding molecule that blocks the apoptotic pathway, ensures the survival during migration into genital ridge. The STRA8 acts in the bigining of germ cells meioses in XX embryos and mark the first sexual gonadal dimorphism. In other hand the subsequently oocyte survival is controlled through transforming growth factor member BMP15, that guarantees granulose cells differentiation that acts indirectly in meiotic oocyte and theca cells differentiation. In this work we searched for the presence of inactivating mutations in NANOS3 and BMP15 in 45 patients with 46XX gonadal dysgenesis (10 familial cases) and 40 patients with secondary amenorrhea without FSHR and SF1 mutation. We also searched for inactivating mutations in coding and proximal promoter region of STRA8 in 45 patients with 46XX gonadal dysgenesis, 16 ovotesticular disorder of sex development (DSD) patients and five 46XX testicular DSD patients all SRY negative and molecular defects in DAX1, WNT4 and SOX9 gene. In NANOS3 we identified the mutation p.E120K in homozygous state, the first associated with DG 46,XX phenotype. This missense mutation was identified in two sisters with 46XX GD and affects a zinc finger domain of the protein. The new variant was absent in 200 control alleles. In BMP15, a new nonsense mutation p.Q115X was identified two sisters in homozygous state and in one sporadic case of secondary amenorrhea in heterozygous state. The premature codon STOP affects the pro-peptide domain of the protein. The new variant was absent in 200 control alleles. In STRA8, only a previously described polymorphism (rs7805859) was identified without any other variation in coding or proximal promoter region. In conclusion, we identified for the fist time mutation in NANOS3 associated with DG 46XX and corroborate the role of BMP15 in this phenotype. Disorders of gonadal development 46,XX may be involved with differentiation and maintenance of ovarian germ cells.

Made available in DSpace on 2016-04-28T14:16:35Z (GMT). No. of bitstreams: 1 Ana Paula Oliveira Pereira de Morais Brito.pdf: 798875 bytes, checksum: c1cd52c0cd418f55bb2b6e65cd0b9ffe (MD5) Previous issue date: 2008-10-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The present research analyses Thomas Hunt Morgan s studies on sex-determination (1900-1913) and tries to elucidate: which were Morgan s main hypotheses to explain such a phenomenon; whether they were well grounded or not and whether there were any changes in his thought in that period. Besides that, it tries to find whether Morgan s contribution concerning sex-determination were significant as compared to those of other scientists of his time, as well as the kind of strategy he used to become the most frequently cited scientist on the subject. This thesis contains an introduction and five chapters. Chapter 1 deals with the hereditary precedents and the general scientific context in which Morgan presented his contributions concerning the subject. It also presents a short account of his career, background and professional interests. Chapter 2 describes the different explanations concerning sex-determination presented by several scientists in the first decade of the 20th century. Chapter 3 discusses some results obtained by Morgan in his studies on sex-determination during the period from 1900 to 1910. Chapter 4 discusses whether the evidence got from Morgan s studies on sex-determination from 1910-11 to 1913 was enough to explain his change of opinion concerning the relationship between sex-determination, chromosomes and Mendel´s principles. Chapter 5 tries to answer the questions presented in the Introduction and provides some final remarks on the subject. This study led to the conclusion that Morgan s belief in a cytoplasmic inheritance of sex-determination till 1910 was grounded on the evidence he got from his embryological studies, as well as his studies on sex-determination in parthenogenetic insects. Even when he admitted in 1909 that chromosomes could contribute in some way to this phenomenon, he supposed that this was a quantitative effect. The evidence got from Morgan s studies from 1910-1911 to 1913 related to sex-linked inheritance in Drosophila, in our view, were not enough to justify his change of mind on the subject by adopting a quantitative Mendelian-chromosome interpretation. Besides that, his old criticisms on the Mendelian chromosome theory as a whole were not answered. This study confirms the interpretation that Morgan s change of view was mainly due to a professional strategy, since he considered this could be a fruitful working hypothesis of work. He admitted students which were of a low academic status in spite of being skilful and well-trained in cytology. Moreover, he chose a cheap and easily breeding experimental material and wrote several works individually or together with his collaborators in a popular style, such as Heredity an sex. Morgan s strategies worked, since after 1910-1911 the works of the Drosophila group were widely cited in the relevant literature / Esta pesquisa, que trata dos estudos de Thomas Hunt Morgan sobre determinação de sexo (de 1900 a 1913), procura elucidar quais foram as principais hipóteses levantadas por Morgan para explicar tal fenômeno; se elas estavam bem fundamentadas; e se houve alguma mudança em seu pensamento durante o período. Além disso, procura saber se as contribuições de Morgan referentes à determinação de sexo foram significativas em comparação àquelas de outros cientistas de sua época, bem como que tipo de estratégia ele utilizou para se tornar o cientista mais citado em relação ao assunto. Esta tese contém uma introdução e cinco capítulos. O primeiro capítulo trata dos precedentes sobre a hereditariedade e o contexto científico em geral em que Morgan apresentou suas contribuições em relação ao assunto. Apresenta também uma curta descrição de sua formação, carreira e interesses profissionais. O capítulo 2 descreve as diferentes explicações para a determinação de sexo que foram apresentadas por diversos cientistas durante a primeira década do século XX. O capítulo 3 discute alguns resultados obtidos por Morgan em seus estudos sobre a determinação de sexo durante o período compreendido entre 1900 e 1910. O capítulo 4 discute se as evidências obtidas nos estudos desenvolvidos por Morgan entre 1910-1911 e 1913 foram suficientes para explicar sua mudança de opinião no que se refere à relação entre determinação de sexo, cromossomos e princípios de Mendel. O capítulo 5 procura responder às perguntas apresentadas na introdução e tece algumas considerações sobre o assunto. Este estudo levou à conclusão de que a visão adotada por Morgan até 1910 baseou-se nas evidências obtidas em seus estudos embriológicos, bem como nos estudos sobre determinação de sexo em insetos partenogenéticos. Quando ele admitiu em 1909 que os cromossomos poderiam contribuir de algum modo, foi de uma maneira quantitativa. As evidências obtidas através dos estudos desenvolvidos por Morgan de 1910-1911 a 1913 relacionadas à herança ligada ao sexo em Drosophila não foram suficientes, a nosso ver, para justificar sua mudança de opinião ao adotar uma interpretação mendeliana-cromossômica, qualitativa. Além disso, suas antigas críticas à teoria cromossômica como um todo não foram respondidas. Este estudo confirma a interpretação de que a mudança de visão por parte de Morgan se deveu principalmente a uma estratégia profissional, uma vez que isso poderia ser uma hipótese de trabalho frutífera. Ele admitiu estudantes que embora tivessem um status acadêmico baixo, eram habilidosos e com treino em citologia. Escolheu um material experimental de custo baixo e que facilitou os cruzamentos. Escreveu trabalhos em estilo popular, como Heredity and sex. Suas estratégias funcionaram, já que a partir de 1910-1911 os trabalhos do grupo Drosophila começaram a ser muito citados na literatura relevante sobre o assunto

La compréhension des mécanismes moléculaires impliqués dans la détermination du sexe chez les plantes à fleurs est primordiale d’un point de vue fondamental et appliqué. Des processus liés à la biosynthèse des hormones, tel que l’éthylène, ou la régulation de l’expression génique via des petits ARN et des facteurs de transcription ont été associés à l’unisexualisation des fleurs chez des espèces dioïques. Cependant, les déterminants contrôlant le sexe chez les plantes sont encore largement méconnus. Le palmier dattier, Phoenix dactylifera L, est une espèce dioïque dont le dimorphisme sexuel est observé très tôt au cours du développement des fleurs. Des gènes différentiellement exprimés (DEGs) ont été identifiés pendant les stades précoces du développement floral mâle et femelle. Pour cela, un transcriptome de référence rassemblant des données d’expression relatives aux deux sexes a été généré. L’analyse d'enrichissement GO des DEGs, a révélé des processus biologiques communs aux mâles et aux femelles, associés au développement reproducteur et à la réponse aux stimuli. Ce résultat indique que des mêmes processus peuvent solliciter des gènes différents au cours du développement floral précoce en fonction du sexe. Cette analyse a également mis en évidence que le développement des fleurs mâles requiert des processus biologiques spécifiques impliqués dans la régulation cellulaire et l'expression des gènes. En outre, deux DEGs femelles, une S-adenosylmethionine synthase et une Flap endonuclease et un DEG mâle, un élément transposable, ont été identifiés dans les régions non-recombinantes du génome du palmier dattier.Cette étude est la première analyse globale des processus biologiques associés à l’acquisition du dimorphisme sexuel. Elle contribue également à la compréhension de la détermination du sexe chez le palmier dattier, et plus largement à la connaissance de ces processus chez les espèces dioïques. / Unraveling molecular mechanisms involved in sex determination in flowering plants is of outstanding basic and applied interest. Several studies on dioecious species have highlighted the molecular basis of sex determination, such as cell death and ethylene biosynthesis pathway. Sex determination mechanisms in plants are, however, still largely unknown. The date palm, Phoenix dactylifera L, is a dioecious species where sexual dimorphism is observed very early in development of flowers. Differentially expressed genes (DEGs) were identified during the early stages of the male and female flower development. A reference transcriptome including male and female data was constructed to gain insight into this process in the dioecious palm Phoenix dactylifera L. Differentially expressed genes (DEG) were subsequently identified between males and females in the early flower development stages in which the first morphological gender difference occurs in date palms.Gene ontology enrichment analysis of DEG revealed biological processes shared between males and females involved in reproductive development and response to stimulus, indicating that same processes could require different genes during early flower development in date palm. This analysis also suggested that date palm triggers biological processes specifically involved in cellular regulation and gene expression to develop male flowers. Furthermore, two female DEGs related to DNA methylation S-adenosylmethionine synthase and DNA metabolism Flap endonuclease, and one male DEGs, a transposable element were found in non-recombinant date palm regions. This study provided the first insight into biological processes involved in sex determination in date palms and more widely to knowledge of this process in dioecious species.

Bien que les sexes séparés (dioecie) soient plus rares que chez les animaux, ∼15 600 espèces dioiques ont évolué chez les angiospermes (∼6% de l'ensemble des espèces). La manière dont le sexe de ces plantes est contrôlé est une question centrale de la biologie végétale, mais également de l'agronomie car de nombreuses plantes cultivées sont des plantes dioiques (∼20% des espèces cultivées) mais dont un seul sexe (généralement les femelles) présente un intérêt agronomique. Pourtant, seulement trois gènes du déterminisme du sexe ont été identifiés à ce jour chez les plantes dioiques, chez le kaki, l'asperge et la fraise. La dioecie a vraisemblablement évolué plusieurs fois chez les angiospermes et il est possible que les gènes du déterminisme du sexe soient divers. Deux voies principales d'évolution vers la dioecie ont été identifiées. Les deux partent d'une espèce dont les fleurs sont hermaphrodites, le régime de reproduction ancestral chez les angiospermes, puis passent soit par un intermédiaire monoique (espèce avec des fleurs unisexuées mâles et femelles sur le même individu), soit par un intermédiaire gynodioique (espèce avec des femelles et des individus avec des fleurs hermaphrodites). Cette thèse a pour objet la comparaison de deux systèmes de plantes représentant ces deux voies. Chez Coccinia grandis, une cucurbitacée ayant également des chromosomes XY, l'évolution de la dioecie est passée par la monoecie. Chez Silene latifolia, une plante dioique bien étudiée avec des chromosomes sexuels XY, l'évolution de la dioecie s'est faite à partir de la gynodioecie. Trois gènes contrôlant la monoecie ont été identifiés chez le melon et il a été proposé que ces gènes soient les gènes du déterminisme dans les espèces dioiques proches du melon comme C. grandis. Nous avons donc opté pour une approche gène candidat dans cette espèce. Très peu de ressources génétiques et génomiques sont disponibles chez C. grandis, et nous avons choisi d'utiliser SEXDETector, une méthode probabiliste qui utilise des données RNA-seq pour génotyper des parents et leurs descendants, et qui infère les gènes lies au sexe sans génome de référence. Cette méthode m'a permis d'identifier 1 364 gènes présents sur les chromosomes sexuels de C. grandis. J'ai établi que les gènes differentiellement exprimés entre les sexes étaient plus abondants sur chromosomes sexuels que sur les autosomes. J'ai également observé des marques de la dégénérescence du chromosome Y chez cette plante, comme des diminutions d'expression ou des pertes de gènes. Enfin, mes résultats démontrent la présence de compensation de dosage chez C. grandis. Le test des gènes candidats est en cours. Chez S. latifolia, 3 grandes régions liées au déterminisme ont déjà été identifiées sur le chromosome Y. Pour identifier les gènes du déterminisme, nous avons choisi de séquencer ce chromosome. Le séquençage des chromosomes Y est encore un défi pour la génomique. La phase d'assemblage est très difficile à cause des répétitions présentes en grand nombre sur ces chromosomes. En conséquence, les séquences complètes de chromosome Y sont très rares, et principalement disponibles chez les animaux. Afin de minimiser les problèmes d'assemblage dus aux répétitions, nous avons utilisé des techniques dites de 3eme génération (avec de grandes lectures). J'ai moi-même généré des données MinION (Oxford Nanopore) à partir d'ADN de chromosome Y. L'assemblage a été réalisé en combinant des données Illumina, PacBio et MinION. Notre assemblage final fait une taille de 563 Mb pour un N50 de 6 114 pb, et contient 16 219 gènes annotés de novo / Although rarer than in animals, separate sexes (dioecy) have evolved in ∼15,600 angiosperm species (∼6% of all angiosperm species). How sex is controlled is a central question in plant sciences and also in agronomy as many crops are dioecious (∼20% of crops) with only one useful sex (usually female). Only three master sex-determining genes have been identified in dioecious plants so far, namely in persimmons, asparagus and strawberry. Dioecy likely evolved several times independently in angiosperms, suggesting that sex-determining genes are of diverse origins. Hermaphroditism is the predicted ancestral state of the angiosperm flower. Two main pathways have been identified that explain the evolution of hermaphroditism towards dioecy: either through a monoecious state (with both unisexual male and female flowers on the same individual) or a gynodioecious state (with females and individuals having hermaphroditic flowers). My aim is to compare two plant systems representing each one of these two pathways. In Coccinia grandis, a Cucurbitaceae with an XY chromosome system, dioecy evolved through monoecy. In Silene latifolia, a well-studied dioecious plant with XY sex chromosomes, dioecy evolved through gynodioecy. Three genes controlling monoecy have been identified in melon, and it was suggested that these genes act as sex-determining genes in closely related dioecious species such as C. grandis. I therefore chose a candidate gene approach in this species. Very few genetic and genomic data are available in C. grandis, and we chose to use SEX-DETector, a probabilistic method that uses RNA-seq data to genotype parents and their offspring, and infers sex-linked genes with no need for a reference genome. This method allowed me to identify 1,364 genes that are present on the sex chromosomes of C. grandis. I found that the sex chromosomes are enriched in sex-biasedgenes when compared to autosomes and I characterized Y chromosome degeneration in terms of decreased expression and gene loss. Finally, I showed that dosage compensation occurs in C. grandis. Testing for the three candidates genes is ongoing. In S. latifolia 3 regions involved in sex determination have already been identified on the Y chromosome. We chose to sequence this chromosome to identify sex-determining genes. The sequencing of Y chromosomes remains one of the greatest challenges of current genomics. The assembly step is very difficult because of their highly repeated content. Consequently, fully sequenced Y chromosomes are rare and mainly available for research in animals. To overcome the difficulty of assembling reads with many repeats, I used third generation sequencing (TGS, producing long reads). I produced a dataset using the Oxford Nanopore MinION sequencer with Y chromosome DNA. Assembling was performed using a combination of Illumina, MinION and PacBio sequencing data. The final assembly had a total length of 563 Mb with a scaffold N50 of 6,114 bp, and contained 16,219 de novo annotated genes

Abstract Mammalian female sex development was considered a default developmental pathway. However, the deletion of the Wnt4 gene, a member of the Wnt family of secreted signals, was shown to reverse the sex of XX female mouse embryo and caused exhibition of certain male characteristics. This indicated that the female sexual development cannot be default but depends on active signaling and cell-cell interaction. The aim of the current study was to reveal the functional role of the Wnt4 gene in the control of sex determination, ovariogenesis and female sex duct formation. This study demonstrates that testosterone is produced by the ovary of Wnt4-deficient female embryos. The inhibition of androgen action by an antiandrogen, flutamide, during gestation leads to complete degeneration of the Wolffian ducts in 80% of the Wnt4 mutant females. This suggests that testosterone is the possible mediator of the masculinization phenotype in Wnt4-deficient females. Wnt4 is expressed by ovarian somatic cells, which are vital for the control of female germline development. This work has shown that Wnt4 is the factor maintaining germ cell cysts, cell-cell interaction and early follicular gene expression. In addition, the findings indicate a critical role for Wnt4/5a signaling in meiosis. Our research has proven that Wnt4 has roles during postnatal ovary development as its defective signaling leads to premature ovarian failure associated with diminished Amh levels, defective basement membrane and cell polarization. The Mullerian duct, the anlagen of oviduct, uterus and upper part of vagina, does not form in Wnt4-deficient females. This study indicates that Wnt4 is needed for migration initiation and maintenance during Mullerian duct formation prenatally. During the postnatal uterine differentiation Wnt4 is essential for endometrial gland formation. The present study provides new evidence for Wnt4 function during embryonic and adult female sexual differentiation. / Tiivistelmä Nisäkkäiden naaraspuolista kehitystä pidettiin aiemmin sukupuolisen erilaistumiskehityksen oletusarvona. Signaloivien proteiinien Wnt-perheeseen kuuluvan Wnt4-geenin puutteen todettiin kuitenkin johtavan XX naarasalkion sukupuolen kääntymisen koiraaksi sekä aiheuttavan tiettyjä koiraille ominaisia piirteitä. Tämä osoitti, ettei naaraspuolinen kehitys ole oletusarvo, vaan se riippuu aktiivisesta signaloinnista ja solujen välisestä interaktiosta. Tämän väitöstutkimuksen tarkoitus oli selvittää Wnt4-geenin roolia sukupuolen määräytymisessä, munasarjojen kehittymisessä sekä naaraan sukupuolitiehyitten muodostumisessa. Tutkimuksessa osoitettiin, että munasarjat tuottavat testosteronia niillä naaraspuolisilla alkioilla, joilta puuttuu Wnt4-geeni. 80 prosentilla naaraista, joilla on Wnt4-geenin puute, androgeenivaikutuksen esto raskauden aikana annettavalla antiandrogeenilla, flutamidilla, estää sukupuolen vaihtumisen fenotyypin. Tämä viittaa siihen, että testosteroni toimii mahdollisena koiraan fenotyypin välittäjänä naarailla, joilta puuttuu Wnt4-geeni. Wnt4 ilmentyy munasarjojen somaattisissa soluissa, jotka ovat tärkeitä naaraspuolisen ituradan kehityksen säätelyn kannalta. Väitöstutkimus osoittaa, että Wnt4 on itusoluryppäitä, solujen välistä interaktiota sekä varhaista follikkeligeeni-ilmentymistä ylläpitävä tekijä. Tulokset osoittavat myös, että Wnt4/5a -signaloinnilla on tärkeä rooli meioosissa. Tutkimus osoittaa lisäksi, että Wnt4 vaikuttaa munasarjojen kehitykseen myös syntymän jälkeen. Puutteellinen signalointi alentaa Anti-Müllerian hormonin tasoa, heikentää tyvikalvoa ja vähentää solujen polarisaatiota, joka johtaa ennenaikaiseen munasarjojen toiminnan hiipumiseen. Müllerin tiehyet, joista myöhemmin kehittyvät munanjohtimet, kohtu ja vaginan yläosa, jäävät kokonaan muodostumatta naarailla, joilta puuttuu Wnt4-geeni. Tulokset viittaavat siihen, että Wnt4 on tarpeen alkioaikaiseen Müllerin tiehyen muodostavien solujen liikkeellelähtöön ja ylläpitoon. Wnt4:llä on myös keskeinen rooli kohturauhasten muodostumisessa sukukypsyyden saavuttamisen aikana ja sen jälkeen.

<div>Chromosomal mechanisms of sex determination vary greatly in phylogenetically closely related species, indicative of rapid evolutionary rates. Sex chromosome karyotypes are generally conserved within families; however, many species have derived sex chromosome configurations. Insects display a plethora of sex chromosome systems due to rapid diversification caused by changes in evolutionary processes within and between species. A good example of such a system are insects in the blow fly family Calliphoridae. While cytogenetic studies observe that the karyotype in blow flies is highly conserved (five pairs of autosomal chromosomes and one pair sex chromosome), there is variation in sex determining mechanisms and sex chromosome structure within closely related species in blow flies. The evolutionary history of sex chromosomes in blow fly species have not been fully explored. Therefore, the objective of this research was to characterize the sex chromosome structures in four species of blow flies and investigate the selective forces which have played a role in shaping the diverse sex chromosome system observed in blow flies. The blow fly species used in this study are Phormia regina, Lucilia cuprina, Chrysomya rufifacies and Chrysomya albiceps. Phormia regina,and Lucilia cuprina have a heteromorphic sex chromosome system and are amphogenic (females produce both male and female offspring in equal ratio). In contrast, Chrysomya rufifacies and Chrysomya albiceps, have a homomorphic sex chromosome system, are monogenic (females produce unisexual progeny), have two types of females (arrhenogenic females – male producers and thelygenic females – female producers), and sex of the offspring is determined by the maternal genotype. </div><div>To accomplish these tasks, a total of nine male and female individual draft genomes for each of the four species (including three individual draft genomes of Chrysomya rufifacies – male, and the two females) were sequenced and assembled providing genomic data to explore sex chromosome evolution in blow flies. Whole genome analysis was utilized to characterize and identify putative sex chromosomal sequences of the four blow fly species. Genomic evidence confirmed the presence of genetically differentiated sex chromosomes in P. regina and L. cuprina; and genetically undifferentiated sex chromosomes in C. rufifacies and C. albiceps. Furthermore, comparative analysis of the ancestral Dipteran sex chromosome (Muller element F in Drosophila) was determined to be X-linked in P. regina and L. cuprina contributing to sex chromosome differentiation but not sex-linked in C. rufifacies and C. albiceps. Evolutionary pressures are often quantified by the ratio of substitution rates at non-synonymous (dN) and synonymous (dS) sites. Substitution rate ratio analysis (dN/dS) of homologous genes indicated a weaker purifying selection may have contributed to the loss of sex-linked genes in Muller element F genes of the undifferentiated sex chromosome as compared to the differentiated sex chromosome system. Overall, the results presented herein greatly expands our knowledge in sex chromosome evolution within blow flies and will reinforce the study of sex chromosome evolution in other species with diverse sex chromosome systems.</div><div><br></div>

In teleosts, elevated temperature during embryogenesis can act on germline cell development, which in turn plays a role for sexual fate. In Nile tilapia, a species with high-temperature-induced masculinization, little is known about the effects of increased temperature on gonadal development in non-masculinized females. The aim of the present work was to investigate persistent effects on the germline of genetically female (XX) Nile tilapia reared at normal (28 ° C) or elevated temperature (36°C) during the critical time of gonadal sex differentiation at 10 to 20 days post fertilization. Nonsex-reversed females were compared to control females to determine persistent effects of temperature on subsequent ovarian development using histological approaches. Germline stem cells were identified using the germline marker Vasa in combination with the proliferation marker PCNA. Vasa- and PCNA-positive germline stem cells were found in ovaries of both high-temperature-treated and control females. In both groups, ovarian germline stem cells were located at the germinal epithelium of the ovigerous lamellae. Although no detrimental effects of high temperature on gonadal development in female Nile tilapia were observed, implications on the reproductive fitness caused by elevated temperature need to be investigated in greater depth.

Les systèmes sexuels et les mécanismes responsables de la détermination du sexe chez les animaux sont issus de stratégies diverses. Cette incroyable diversité se reflète notamment chez les bivalves, où autant les facteurs génétiques qu’environnementaux y jouent un rôle, avec des espèces utilisant divers modes de reproduction, tels que le gonochorisme ou l’hermaphroditisme simultané ou séquentiel. La découverte la plus notable est celle d’un système de déterminisme sexuel unique qui impliquerait les mitochondries. Spécifiquement, un système de transmission sexe-spécifique de l’ADN mitochondrial, connu sous le nom de DUI (« Double Uniparental Inheritance » ou double transmission uniparentale), serait lié au maintien du gonochorisme chez certaines espèces de bivalves. La DUI implique un ADN mitochondrial qui est transmis de façon maternelle (ADNmt F) aux femelles et aux mâles, et l’autre transmis de façon paternelle (ADNmt M) aux mâles seulement. Les ADNmt F et M chez les espèces à DUI sont caractérisés par des traits uniques, comme une modification du gène cox2, ou encore la présence de nouveaux gènes associés à chacun des génomes mitochondriaux (des gènes sexe-spécifiques) qui ont une fonction autre que la production d’énergie contrairement aux autres gènes mitochondriaux typiques. Le lien entre la DUI et la détermination du sexe étant encore flou, trois approches ont été proposées pour aider à le démystifier, chacune des approches constituant un chapitre de cette thèse. Les deux premiers chapitres se sont concentrés sur des espèces de moules d’eau douce de l’ordre des Unionida, où une corrélation entre gonochorisme et DUI et hermaphroditisme et SMI (« Strictly Maternally Inheritance » ou transmission strictement maternelle) a été décrite. La première approche consistait à produire une analyse transcriptomique comparative entre les gonades mâles et femelles de deux espèces à DUI gonochoriques, Venustaconcha ellipsiformis et Utterbackia peninsularis (famille Unionidae), pour mieux comprendre les mécanismes sous-jacents à la détermination du sexe et à la DUI chez ces bivalves. Cette étude a révélé 12 000 gènes orthologues, avec 2 583 gènes différentiellement exprimés chez les deux espèces, dont les gènes Sry, Dmrt1 et Foxl2 connus pour être des éléments clés dans la détermination du sexe chez les vertébrés et d’autres bivalves. Nos résultats ont aussi été comparés avec d’autres espèces à DUI, notamment avec la palourde marine Ruditapes philippinarum, pour identifier des éléments partagés entre des espèces éloignées qui pourraient être responsables de la régulation de la DUI. Globalement, ces résultats corroborent l'hypothèse selon laquelle un mécanisme d'ubiquitination modifié pourrait être responsable de la rétention de l'ADNmt paternel chez les bivalves mâles. Les analyses ont aussi révélé que la méthylation de l'ADN pourrait être impliquée dans la régulation de la DUI. Une deuxième analyse transcriptomique comparative a été réalisée afin de discerner les mécanismes sous-jacents à la détermination du sexe et à la DUI, mais cette fois-ci entre l’espèce à DUI gonochorique U. peninsularis et l’espèce proche parente à SMI hermaphrodite U. imbecillis. Cette étude a permis de supporter l’hypothèse d’une implication des mécanismes d’ubiquitination et de méthylation dans la régulation de la DUI, ainsi que de confirmer un rôle des gènes conservés liés à la détermination du sexe également chez les bivalves hermaphrodites. Nos résultats ont également révélé de nouveaux gènes candidats ayant des rôles potentiels dans la DUI, y compris des nucléases et des facteurs impliqués dans l’autophagie / mitophagie. Finalement, afin d’identifier des éléments génétiques mitochondriaux qui pourraient faire partie des mécanismes sous-jacents à la DUI et la détermination du sexe chez les bivalves, nous avons séquencé les ADNmt F et M complets de deux nouvelles espèces à DUI de deux familles de l’ordre des Venerida, Scrobicularia plana (famille Semelidae) et Limecola balthica (famille Tellinidae). En effet, la description complète des ADNmt chez les espèces à DUI a été effectuée chez plusieurs espèces de moules d’eau douce (ordre Unionoida), mais peu d’espèces l’ont été pour les ordres Mytilida et Venerida. Ces études sont essentielles pour retracer des signatures génétiques mitochondriales partagées par différentes espèces à DUI. Nos résultats ont révélé les plus grosses différences de taille (>10kb) et de divergence nucléotidique (jusqu’à 50% de divergence) entre les ADNmt M et F, parmi toutes les espèces à DUI. Ces différences de taille sont principalement dues à une immense insertion (>3.5kb) dans la séquence du gène cox2 du génome mitochondrial M, chez nos deux espèces, un trait précédemment décrit chez les moules d’eau douce. Le gène cox2 des mâles de S. plana est la plus longue séquence à travers le règne animal. Une autre fonctionnalité importante portés par les ADNmt F et M est la présence de nouveaux gènes spécifiques au sexe, comme reportée chez toutes les autres espèces à DUI jsuqu’à maintenant. Les résultats combinés de cette thèse soutiennent le partage de plusieurs éléments génétiques clés entre les espèces à DUI. De plus, un parallèle avec le système CMS (« Cytoplasmic Male Sterility » ou stérilité cytoplasmique mâle) chez les plantes, les seuls autres organismes possédant un déterminisme sexuel qui implique les mitochondries, est proposé pour expliquer le rôle de l’ADNmt dans la détermination du sexe chez les espèces de bivalves à DUI. / Sexual systems and sex determining mechanisms described among animals are extraordinarily diverses. This amazing diversity is present in bivalves where both environment and genetic factors occur, leading to, among others, gonochoric and simultaneous or sequential hermaphroditic species. The most impressive discovery is a sex-determining system that would involve mitochondria. Specifically, a unique mitochondrial DNA inheritance system, known as Doubly Uniparental Inheritance (DUI), would be related to the maintenance of gonochorism in some bivalve species. DUI involves two mitochondrial DNA lineages, one that is maternally transmitted (F mtDNA) to females and males, and the other that is transmitted paternally (M mtDNA) to males only. The F and M mtDNAs, in DUI species, are characterized by unique traits, such as a modification of the cox2 gene, or the presence of new genes associated with each of the mitochondrial genomes (sex-specific genes) that have a function other than energy production, unlike other typical mitochondrial genes. Since the link between DUI and sex determination is still unclear, three approaches have been proposed to help demystify it, with each of the approaches constituting a chapter of this thesis. The first two chapters focused on freshwater mussel species of the order Unionida, where a correlation between gonochorism and DUI and hermaphroditism and SMI (Strictly Maternally Inheritance) was described. The first approach was to produce a comparative transcriptomic analysis between the male and female gonads of two gonochoric DUI species; Venustaconcha ellipsiformis and Utterbackia peninsularis (Unionidae family), to better understand the mechanisms underlying sex determination and DUI in these bivalves. This study revealed 12,000 orthologous genes, with 2 583 genes differentially expressed in both species, including Sry, Dmrt1, and Foxl2 known to be key sex-determining genes in vertebrates and other bivalve species. Our results were also compared with other DUI species, including the marine clam Ruditapes philippinarum, to identify shared elements between distant species that may be responsible for DUI regulation. Overall, these results support the hypothesis that a modified ubiquitination mechanism may be responsible for the retention of paternal mtDNA in male bivalves. The analyzes also revealed that DNA methylation could be involved in DUI regulation. 7 A second comparative transcriptomic analysis was performed to discern the mechanisms underlying sex determination and DUI between the gonochoric DUI species, U. peninsularis, and the closely related SMI hermaphroditic species, U. imbecillis. This study supported the hypothesis of an involvement of ubiquitination and methylation mechanisms in DUI regulation, as well as confirmed a role of conserved genes related to sex determination in hermaphroditic bivalves. Our results also revealed novel candidate genes with potential roles in DUI, including nucleases and factors involved in autophagy / mitophagy mechanisms. Finally, to identify mitochondrial genetic elements that could be part of the mechanisms underlying DUI and sex determination in bivalves, we sequenced the complete F and M mtDNAs of two new DUI species, from two families of the order Venerida; Scrobicularia plana (Semelidae family) and Limecola balthica (Tellinidae family). The complete description of mtDNAs in DUI species has been carried out for several species of freshwater mussels (Unionoida order), but very few species have been described for the orders Mytilida and Venerida. Such studies are essential for tracing mitochondrial genetic signatures shared by different DUI species. Our results revealed the largest differences in size (>10kb) and nucleotide divergence (up to 50% divergence) between M and F mtDNAs, among all DUI species. These differences in size are mainly due to a huge insertion (> 3.5kb) in the cox2 gene of the M mtDNA from both species, a trait previously described in freshwater mussels. The cox2 gene in S. plana males represents the longest cox2 sequence across the animal kingdom. Another important feature of F and M mtDNAs is the presence of new sex-specific genes, as reported in all other DUI species so far. The combined results of this thesis support the sharing of several key genetic elements among DUI species. In addition, a parallel with the Cytoplasmic Male Sterility (CMS) system in plants, the only other organisms with a sex determination system that involves mitochondria, is proposed to explain the role of mtDNA in sex determination in DUI bivalve species.

L’accroissement de la population humaine mondiale a des répercussions majeures, ce n’est donc pas surprenant, compte tenu de la nécessité de nourrir une population grandissante au niveau planétaire, que la production en conchyliculture ait augmenté au cours des dernières décennies. Or, les connaissances acquises concernant les divers facteurs du déterminisme du sexe et du rapport des sexes chez les bivalves sont très limitées et cela pourrait ralentir grandement le taux de production des éleveurs et leur capacité à intervenir si les stocks venaient à diminuer de façon inquiétante. Certains travaux mentionnent que certains facteurs environnementaux, comme la température, auraient un effet sur le rapport des sexes chez une variété de bivalves, incluant la moule bleue commerciale Mytilus edulis, quoiqu’aucune étude n’ait validé cette dernière possibilité. Cela dit, il est possible que l’environnement des adultes puisse aussi affecter le phénotype de la progéniture. En effet, une transmission intergénérationnelle a déjà été identifiée chez Mytilus, mais la possibilité que les conditions des parents affectent le rapport des sexes spécifiquement n’a jamais été abordée. Il est toutefois connu qu’un facteur maternel présent dans l’œuf affecte le sexe de la progéniture et que cette espèce de bivalve a un mode de transmission des mitochondries particulier. Ce mode de transmission appelé « transmission doublement uniparentale » a rendu possible l’identification du sexe chez les embryons. De cette façon, 1938 embryons provenant de 25 croisements artificiels réalisés à trois températures et effectués lors de trois différentes années ont été analysés. Nos analyses mettent en évidence une variation significative dans la proportion de larves femelles entre les années passant de 64 % à 98 %. Dans certains cas, la proportion de femelle varie de 0 à 100 % entre les différents traitements. Même si un effet général sur le rapport des sexes n’était pas significatif, chaque croisement s’est avéré avoir une norme de réaction qui lui est propre face aux 3 différentes températures. Cette étude met en valeur l’effet important de l’environnement sur le déterminisme du sexe chez M. edulis, autant chez les parents que lors du développement des embryons. / The factors affecting sex determination still remain unknown for most bivalve species. Some studies reported that environmental factors, such as temperature, influence sex determination in certain species, and this has been hypothesized also for the blue mussel Mytilus edulis, but not experimentally validated yet. Adult exposure to different environmental conditions during gametogenesis, which occurs seasonally, may also affect offspring phenotype, including sex determination. Intergenerational carryover effects have been reported in bivalves, but the impact of parental exposures on offspring sex determination has not been examined so far. To address these questions, artificial fertilizations were performed on individuals collected in three different years and their embryos and larvae were reared at three different temperatures to specifically test if the environment influence offspring sex ratio through effects on parental developing gametes and/or on developing embryos. We took advantage of the doubly uniparental inheritance of mitochondria in bivalves to determine the sex of the larvae. The analysis of 1938 larvae from 25 crosses revealed that the overall proportion of female larvae was significantly different among years, varying from 64 % to 98 %. While the proportion of female larvae across temperature ranged from 0 to 100 % in some cases, the reaction norms were cross-specific and there were no significant effects of rearing temperature on sex ratio. Taken together, our results suggested that sex determination in M. edulis occur during the gametogenesis according to the genotype of the parents, but could also be changed during the development. More importantly, both processes are strongly affected by environmental conditions.