No description available.

The synthetic estrogen 17α-ethinylestradiol (EE2) is an endocrine disrupting chemical (EDC) of concern due to its persistent nature and widespread presence in the aquatic environment. In mammals, effects of developmental EDC exposure on reproduction and behavior not only persist to adulthood after discontinued exposure, but are also inherited by several consecutive unexposed generations. The results presented in this thesis demonstrate that non-reproductive behavior in fish is highly sensitive to the influence of EE2 during development and the effects do not appear to be restored after a long recovery period in clean water. We have shown that exposure to low doses of EE2 during development results in increased anxiety in two fish species (zebrafish and guppy) and their offspring. We have also demonstrated that the effects of EE2 on anxiety are apparent in both sexes and are transgenerationally transmitted to two consecutive generations of unexposed offspring in the guppy. In order to investigate the possible biological mechanisms of the observed persistent effects on non-reproductive behavior, we also performed an RNA sequencing analysis of the whole-brain transcriptome in developmentally exposed zebrafish after remediation in clean water until adulthood. Differential expression of 33 genes in males and 62 genes in females were observed as a result of EE2 exposure, with only one gene affected in both sexes. Functional analysis revealed cholesterol biosynthesis and circadian rhythm to be the top two affected pathways in males and females, respectively. Both pathways have previously been implicated in anxiety behavior and represent possible candidates connecting the transcriptome alterations to the observed behavioral phenotype. The study represents an initial survey of the fish brain transcriptome by means of RNA sequencing after long-term recovery from developmental exposure to an estrogenic compound.

Chez l’homme, des données cliniques décrivent une association entre des pathologies hépatiques et des désordres de la fertilité masculine. Plusieurs modèles expérimentaux de cholestase ont permis de confirmer ce lien et de souligner un impact sur la physiologie testiculaire. De manière intéressante, une telle corrélation existe aussi bien à l’âge adulte que dans des modèles animaux en période pré-pubertaire. Pour autant, le lien moléculaire pouvant expliquer cette association physiopathologique n’a pas été exploré. L’ensemble des hépatopathies a pour dénominateur commun une augmentation des taux plasmatiques d’acides biliaires et ce dès les stades les plus précoces de la maladie. Dans ce contexte, l’hypothèse de l’impact délétère des acides biliaires sur la fonction reproductrice reste à définir. Notre projet de recherche s’articule autour de l’analyse d’un modèle murin d’atteinte hépatique induite par un régime supplémenté en acide cholique. Nos résultats principaux montrent que : 1) lors d’une exposition pubertaire, l’activation supra-physiologique des signalisations Fxrα conduit à un défaut de maturation sexuelle associé à une altération de la fonction endocrine du testicule ; 2) dans un contexte d’exposition à l’âge adulte, l’activation excessive du récepteur membranaire Tgr5 par les acides biliaires est associées à une hypofertilité. Celle-ci s’accompagne d’une altération de la spermatogenèse consécutive à un détachement progressif de l’épithélium séminifère et à une apoptose spécifique des spermatides ; 3) enfin, nos conclusions démontrent pour la première fois l’impact transgénérationnel de l’exposition aux acides biliaires. Sur deux générations successives, les descendants des mâles adultes nourris par un régime supplémenté en acide cholique présentent des anomalies développementales et métaboliques. Dépendantes de l’action de Tgr5, ces dernières sont attribuées à des altérations de l’épigénome des spermatozoïdes issus des mâles exposés aux acides biliaires. En conclusion, nos données démontrent que, dans des conditions cholestatiques, les acides biliaires altèrent les fonctions de reproduction notamment par leurs impacts sur les fonctions testiculaires. Au regard du nombre croissant de personnes souffrant de troubles hépatiques, ces effets délétères des acides biliaires pourraient contribuer à l’augmentation de l’incidence de l’infertilité masculine. Des molécules agonistes des signalisations FXRα et TGR5 sont aujourd’hui envisagées dans le cadre du traitement de pathologies courantes de notre société. Dans ce contexte, notre étude permettra d’alerter les instances sanitaires quant aux conséquences de l’accès à de tels traitements sur la fertilité et la santé des générations futures. / Clinical data describe an association between liver diseases and disorders of male fertility. Several experimental models of cholestasis have confirmed this link and highlight an impact on testicular physiology. Interestingly, such correlation exists in adult as well as in during pre-pubertal animals. However, the molecular links have not been explored yet. The increase of plasma bile acids levels is a common feature of liver diseases. In this context, the hypothesis of the deleterious impact of bile acids on reproductive function remains to be defined. For that purpose, we used a mouse model of liver injury induced by a diet supplemented with cholic acid. Main results show that: 1) supra-physiological activation of Fxra, during pubertal period, alters endocrine function of the testis and then sexual maturation. 2) during adult age excessive activation of membrane receptor TGR5 by bile acids leads to subfertility. This is associated with impaired spermatogenesis due to a detachment of the seminiferous epithelium and specific apoptosis of spermatids. 3) Finally, we show for the first time the transgenerational impact of bile acid exposure. Two generations of progenies from males exposed to bile acid-diet show developmental and metabolic abnormalities. These effects, mediated by TGR5, are correlated with alterations of the spermatozoa epigenome. In conclusion, our data demonstrate that bile acids affect reproductive functions with impacts on testicular functions. In line with the increasing number of people with liver diseases, the deleterious effects of bile acids may contribute to the incidence of male infertility. Interestingly, agonists of FXRα and TGR5 are now considered in the treatment of several diseases. In this context, our study might alert health authorities regarding the potential consequences of these treatments on fertility and health futures generations.

Durant ma thèse, j’ai étudié l’implication d’un variant du récepteur aux œstrogènes α, ERα36, dans l’initiation et la progression du cancer du sein. Au laboratoire, son expression dans les cancers testiculaires avait été montrée comme étant inductrice de la prolifération cellulaire in vitro et in vivo après une exposition à un mélange de polluants environnementaux, considérés comme perturbateurs endocriniens oestrogéno-mimétique : les alkylphénols. Une analyse rétrospective d’échantillons de tumeurs mammaires a montré, par la modélisation de réseaux d’interactions géniques, que l’expression d’ERα36 était corrélée avec l’expression de marqueurs de migration cellulaire, caractéristiques de la progression tumorale. La surexpression d’ERα36 par transfection in vitro et dans un modèle unique de souris Knocked In exprimant ERalpha36 dans la glande mammaire ont montré qu’ERα36 est suffisant pour altérer le phénotype épithélial des cellules mammaires saines. Une exposition aux alkylphénols qui stimulent son expression endogène accentue les altérations cellulaires observées et contribue à l’acquisition transgénérationnelle de propriétés relatives à une transformation tumorale. Les analyses de ce projet pluridisciplinaire se sont appuyées sur des expertises biologiques, mathématiques et bioinformatiques et ont permis de mettre en évidence pour la première fois le rôle potentiel d’ERα36 dans l’initiation tumorale et de confirmer son implication dans la progression du cancer du sein. Enfin, nous avons montré que l’exposition à des doses environnementales d’alkylphénols lors de la période de périnatalité peut conduire à une modification transgénérationnelle de la différenciation de la glande mammaire sous le contrôle d’ERα36 et ainsi augmenter le risque de cancer mammaire / This work was dedicated to study how a variant of estrogen receptor α, ERα36, acts in initiation and progression of breast cancer. In the laboratory, his expression in testicular cancer was shown to stimulate cell proliferation in vitro and in vivo after environmental pollutant exposure. The compounds studied, the alkylphenols, are endocrine disruptors, interfering with normal estrogen signaling. Gene interaction network modelling from retrospective analysis of breast cancer samples showed that ERα36 expression was correlated with the expression of cell migration markers, typical of tumor progression. In vitro ERα36 overexpression and in a unique mouse Knocked In model, expressing ERα36 in the mammary gland, showed that ERα36 is sufficient to alter epithelial phenotype of normal breast cells. Alkylphenols exposure, that stimulated ERα36 endogenous expression, increased cellular alterations and contributed to transgenerational acquisition of properties related to neoplastic transformation. Analysis of this multidisciplinary project were based on biological expertise, mathematics and bioinformatic tools. These results enabled to highlight for the first time the potential role of ERα36 in tumor initiation and confirmed his involvement in breast cancer progression. Finally, we showed that exposure to environmental doses of alkylphenols during the perinatal period can lead to transgenerational modification of mammary gland differentiation under ERα36 control and eventually may increase breast cancer risk

No description available.

Hintergrund: Traumatische Erfahrungen in Kindheit und Jugend sowie über die Lebensspanne werden mit negativen Auswirkungen auf die psychische und physische Gesundheit der betroffenen Person in Verbindung gebracht. Chronischer Stress und traumatische Erfahrungen stehen zudem im Zusammenhang mit Veränderungen des körpereigenen Stresssystems. Diese Auswirkungen können über die betroffene Person hinaus auch die nächste Generation beeinflussen und deren Entwicklung beeinträchtigen. Während der Schwangerschaft ist intergenerationale Transmission über biologische Pfade denkbar. Daher soll untersucht werden, ob sich mütterliche und kindliche Haarcortisolkonzentration (HCC) als Marker für chronisches Stressgeschehen infolge von traumatischen Erfahrungen der Mütter verändert. Hypothesen: 1. Es wurde angenommen, dass es Unterschiede in der HCC zwischen traumatisierten und nicht traumatisierten Müttern und ihren Kindern gibt. 2. Zudem wurden Zusammenhänge erwartet zwischen dem Ausmaß der Traumatisierung und HCC bei Müttern und Kindern. 3. Es wurde angenommen, dass Kinder traumatisierter Mütter 14 Monate nach Geburt mehr Entwicklungsdefizite zeigen und 4. der Zusammenhang zwischen Traumatisierungserfahrung der Mütter und Entwicklungsoutcome der Kinder über mütterliches und/oder kindliches HCC mediiert wird. Methode: Traumatische Erfahrungen in Kindheit und Jugend wurden erfasst über den Childhood Trauma Questionnaire (CTQ); traumatische Erfahrungen über die Lebens-spanne über die Posttraumatic Diagnostic Scale (PDS). Cortisol wurde über Haaranalysen bei 301 Müttern und 210 Kindern untersucht – die Haarproben der Mütter wurden max. 6 Wochen vor Geburt entnommen, die der Kinder bis zu drei Wochen postpartal, um die intrauterine Glucocorticoidregulation abzubilden. Mittels Einfaktorieller Varianzanalysen wurde auf Unterschiede in der HCC zwischen Müttern mit und ohne traumatischer Vorerfahrung getestet. Korrelationsanalysen wurden eingesetzt, um Zusammenhänge zwischen dem Ausmaß der Traumaerfahrung und der HCC, sowie zwischen dem Schweregrad der Traumatisierung und dem Entwicklungsoutcome der Kinder zu untersuchen. Eine Mediationsanalyse diente bei einer kleineren Stichprobe, die durch den späteren Messzeitpunkt resultierte (261 Mütter und 187 Kinder), dazu, 14 Monate nach Geburt, zu prüfen, ob HCC als Mediator für kindliches Entwicklungsoutcome – gemessen über den Ages and Stages Questionnaire (ASQ––3), angenommen werden kann. Ergebnisse: Es zeigte sich ein signifikanter Unterschied hinsichtlich der langfristig integrierten HCC der Mütter, in Abhängigkeit vom Erleben traumatischer Erfahrungen über die Lebensspanne. Hierbei wiesen die Mütter mit mindestens einem traumatischen Ereignis über die Lebensspanne höhere HCC–Werte auf als nicht traumatisierte Mütter. Je schwerer die mütterliche Traumatisierung im Kindes– und Jugendalter war, desto höher war die mütterliche HCC–Konzentration. Bei den Kindern zeigten sich keine signifikanten Unterschiede im HCC. Ein signifikanter Zusammenhang zwischen dem Maß an Traumatisierung in Kindheit und Jugend der Mütter und kindlichen Entwicklungsoutcomes konnte nur bezüglich eines verbesserten Problemlöseverhaltens der Kinder nachgewiesen werden. Weder die mütterliche noch die kindliche HCC konnte als Mediator zwischen mütterlicher Traumatisierung und kindlichem Entwicklungsoutcome bestätigt werden. Schlussfolgerungen: Das Erleben traumatischer Erfahrungen in Kindheit und Jugend und auch über die Lebensspanne scheint Veränderungen in der Stressbiologie der Mütter, nicht aber ihrer Kinder, nach sich zu ziehen. Kinder traumatisierter Mütter zeigten in der Untersuchung keine auffälligen HCC–Konzentrationen und keine Beeinträchtigungen in ihrer Entwicklung 14 Monate nach Geburt. Zukünftige Studien sind erforderlich, die eine transgenerationale Weitergabe von Traumaerfahrungen über einen längeren Zeitraum und auch unter Berücksichtigung der psychischen Gesundheit der Nach-kommen berücksichtigen. / Background: Traumatic experiences in childhood and adolescence as well as across the lifespan are associated with negative effects on mental and physical health of the affected individual. Chronic stress and traumatic experiences have also been related to changes in the body's stress system. These effects may extend beyond the affected individual to the next generation, potentially impacting their development. During pregnancy transgenerational effects may occur via biological pathways. Thus, we investigate whether maternal and child hair cortisol concentrations (HCC) as a marker for chronic stress events altered following maternal traumatic experiences. Hypotheses : 1. Differences in HCC were assumed between traumatised and non–traumatised mothers and their children. 2. In addition, correlations were expected between the extent of traumatisation and HCC in mothers and children. 3. It was assumed that children of traumatised mothers show more developmental deficits 14 months after birth and 4. that the connection between the traumatisation experience of the mothers and the developmental outcome of the children was mediated by maternal and/or child HCC. Method: Traumatic experiences in childhood and adolescence were assessed by the Childhood Trauma Questionnaire (CTQ); traumatic experiences across the lifespan by the Posttraumatic Diagnostic Scale (PDS). Cortisol was analysed in hair samples of 301 mothers and 210 children – the hair samples of the mothers were taken max. 6 weeks before birth, those of the children up to three weeks postpartum, in order to map intrauterine glucocorticoid regulation. Single–factor analyses of variance were used to test for differences in HCC between mothers with and without previous traumatic experience. Correlational analyses were utilized to investigate associations between the extent of trauma experience and HCC as well as between severity of traumatization and child developmental outcomes. Mediation analysis was used in a smaller sample, resulting from the later measurement time (261 mothers and 187 children) to test, 14 months after birth, whether HCC can be assumed to be a mediator of child developmental outcome – measured via the Ages and Stages Questionnaire (ASQ–3). Results: There was a significant difference in the long–term integrated HCC of the mothers, depending on the existence of traumatic experiences over the life span. Here, mothers with at least one traumatic event over the lifespan had higher HCC levels than non–traumatised mothers. The higher the severity of maternal traumatization in child-hood and adolescence, the higher the maternal HCC concentration. There were no significant differences in HCC among the children. A significant correlation between the level of trauma in childhood and adolescence of the mothers and child developmental outcomes could only be demonstrated with regard to improved problem–solving behavior of the children. Neither maternal nor child HCC could be confirmed as a mediator between maternal traumatization and child developmental outcome. Conclusions: Experiencing traumatic experiences in childhood and adolescence and also across the lifespan seems to result in changes in the stress biology of mothers, but not of their children. Children of traumatized mothers showed no noticeable HCC concentrations and no impairments in the study with regard to their development 14 months after birth. Future studies are needed that consider transgenerational transmission of trauma experiences over time and also examine the mental health of offspring.

Ce travail a pour objectif d’explorer les altérations de l’ADN et leurs conséquences potentielles pour les traits d’histoire de vie (survie, croissance et reproduction) d’un invertébré aquatique, Daphnia magna exposé à l’uranium appauvri. La démarche expérimentale vise à évaluer l’accumulation et la transmission des altérations de l’ADN suite à une exposition sur deux générations successives (F0 et F1). Différents scénarios d’exposition mis en place pour tester la sensibilité spécifique de divers stades de vie. Lors d’expositions continue et post-éclosion, les résultats mettent en évidence une accumulation et une transmission des dommages à l’ADN au fil des générations en parallèle de la sévérité des effets. Les altérations de l’ADN sont reportées dès l’éclosion de F1 dès 2 µg.L 1. Les effets sur la croissance et la reproduction sont plus sévères lorsque le stade embryonnaire est exposé et restent visibles dès 9,9 µg.L-1 malgré un retour en milieu non contaminé à l’éclosion. Les résultats suggèrent que les dommages à l’ADN pourraient être des indicateurs précoces de futurs effets sur les traits d’histoire de vie. Une analyse mécanistique des résultats expérimentaux est conduite à l’aide du modèle DEBtox afin de mieux cerner les causes de l’aggravation des effets au cours des générations. Un modèle à deux facteurs de stress (l’un corrélé à la concentration d’exposition et l’autre à un niveau de dommages) est développé. Les ajustements suggèrent l’implication d’un second mode d’action (une augmentation des coûts de croissance et de maturation) pour expliquer les effets immédiats de l’uranium sur la nutrition et les conséquences des dommages accumulés au fil des générations. / This PhD work explored how depleted uranium alters DNA and affects life history traits (survival, growth and reproduction) of an aquatic invertebrate, Daphnia magna. An experimental study is performed to evaluate DNA accumulation and transmission during an uranium exposure over two successive generations (F0 and F1). Different exposures scenarios are achieved to test the specific sensitivity of several life stages to uranium. Genotoxic effects are estimated using random amplified DNA technique combined with PCR. In continuous and post-hatching exposure scenarios, results highlighted an accumulation and a transmission of DNA damage across generations with an increase in effect severity. DNA alterations are reported at hatching of F1 at 2 µg L-1. Effects on growth and reproduction are stronger when the embryo stage is exposed and remain visible at 9.9 µg L-1 despite a return in a clean medium at hatching. Results suggest that DNA damage could be used as early indicators of future effects on life history traits. A mechanistic analysis of experimental results is conducted using a DEBtox model to better understand the causes of the increase in effect severity across generations. A model with two stress factors (one correlated to external concentration and another correlated to a damage level) is developed. Results of fits suggest the involvement of one second mode of action (increase in costs for growth and maturation) to explain immediate effects of uranium on nutrition and consequences of cumulated damage across generations.

Afin de protéger durablement les écosystèmes face aux rejets planifiés ou accidentels de radionucléides dans l’environnement, il est essentiel d’évaluer l’impact de l’exposition des organismes aux radiations ionisantes sur le long terme, à l’échelle de plusieurs générations. Dans ce contexte, ce travail de doctorat vise à améliorer la caractérisation des processus moléculaires et la prédiction des effets transgénérationnels lors d’une exposition aux radiations gamma. Une approche expérimentale concerne l’étude des modifications épigénétiques radio-induites, c’est-à-dire des modifications des mécanismes régulant l’activité des gènes sans modification de la séquence d’ADN elle-même et de leur transmission au fil des générations. Cette étude a permis de mettre en évidence que certaines modifications de la méthylation de l’ADN, l’un des mécanismes épigénétiques les plus étudiés, peuvent être transmises par la lignée germinale aux les générations non-exposées (génération F3) suite à une exposition parentale (génération F0) externe aux radiations gamma (6,5 µGy.h-1 et 41,3 mGy.h-1) pendant 25 jours. Dans une seconde approche, un modèle mécaniste DEBtox (Budget Energétique Dynamique appliqué à la toxicologie) est modifié pour permettre l’analyse des effets des radiations gamma sur la croissance et la reproduction de D. magna à l’échelle de plusieurs générations. Pour ce faire, on utilise des compartiments de dommage, dont le niveau peut être hérité d’une génération à la suivante. Le modèle est ajusté aux données avec des méthodes d’inférence bayésienne afin d’estimer les paramètres tout en tenant compte des incertitudes qui leur sont associées. / In order to durably protect ecosystems facing planned or accidental releases of radionuclides, the long-term impact of organism exposure to ionizing radiation must be studied on a multigenerational scale. The aim of this PhD is to improve the characterization of molecular processes and the prediction of transgenerational effects during a gamma irradiation. First, an experimental approach investigated on radio-induced modifications of epigenetic processes, i.e. changes in mechanisms that regulate gene expression without changing DNA sequence itself and on the transmission of these modifications to subsequent generations. Significant changes in DNA methylation, a well-studied epigenetic mechanism, detected in generation F3 clearly showed that epigenetic modifications could be transmitted to unexposed generations, in response to the exposure of a parental generation (F0) to external gamma radiation (6.5 µGy.h-1 et 41.3 mGy.h-1) for 25 days. Second, a mechanistic modelling approach used a modified version of the DEBtox model (Dynamic Energy Budget model applied to toxicology) in order to analyze effects of gamma radiation on D. magna growth and reproduction over several generations. To that end, damage compartments, with damage levels that were transmitted from one generation to the next, were included. The model was fitted to data using Bayesian inference methods, in order to estimate the parameters while considering their associated uncertainty.

Tomato (Solanum lycopersicum L.) consumption has increased every year due to the fruit attractiveness, several utilizations, and beneficial effects for human health. However, tomato fruits can accumulate a Cd concentration that exceeds the safety threshold for human consumption of vegetables, even when plants are grown in soil with acceptable Cd level. Cd is a non-essential, hazardous element to biological systems, triggering several diseases in humans. In plants, Cd disturbs the antioxidant machinery, changes the nutritional status, and impairs the photoassimilate production and/or partitioning, hence reducing fruit yield and quality. However, distinct tomato accessions can present contrasting tolerance degree to Cd toxicity, as detected by our group in previous studies. The use of these accessions is a powerful approach to identify strategies employed by plants to cope with Cdinduced challenges, and the acknowledgement of such strategies can be potentially used in breeding and biotechnological programs to improve fruit yield and quality in crops that were cultivated in contaminated fields. The set of studies that compose the present thesis aimed (i) to identify the main mechanisms for the contrasting tolerance degree to Cd-induced toxicity in tomato accessions after short and long-term Cd exposure; (ii) to evaluate the relationship among tolerance degree and fruits attributes in plants that were grown in Cd-containing soil, and (iii) to determine the transgenerational effects of Cd-induced stress. In the first experiment, nine tomato accessions with a varied tolerance degree, which was based on biomass accumulation, to Cd exposure were grown in hydroponic solution containing CdCl2 35 μM for 6 days. Avoidance of high Mg concentration in roots was identified as a plant strategy to mitigate Cd toxicity by preventing formation of root hairs. Regarding the mode of action of Cd toxicity, Mn excess in leaves, in addition to the high Cd concentration per se, seems to be coupled to leaf damages that are enhanced by the increased Zn and B concentrations in the photosynthetic tissues. In the second experiment, tolerant (Yoshimatsu) and sensitive (Tropic Two Orders) genotypes were grown in Cd-containing soil, in order to evaluated production parameters. After plant exposure to Cd, the tolerant genotype presented an increased fruit diameter, height and weight, when compared to the control plants. In both cultivars, Cd concentration varied according to the following descending order: roots = leaf blade > (floral receptacle, peduncle and sepals) > stem = fruit peel = fruit pulp. Moreover, data suggested that floral receptacle and its related-structures acted as a barrier to the Cd transportation to the fruits, but it was not enough to avoid Cd reaching the fruits. Furthermore, Cd exposure provoked remarkable reductions in the Mg concentration in roots of sensitive and tolerant genotypes, revealing that both tomato cultivars are able to employ this mechanism for plant acclimation to long-term Cd exposure. Considering such information, it is possible that, under the short-term Cd exposure, tolerant accessions activate this mechanism either early or faster than sensitive genotypes. In addition, positive transgenerational effects on seed germination and vigor of the tolerant genotype were triggered by the plant-mother cultivation in Cd-containing media, despite of the increased chromosomal abnormality. This work reported new insights about the effects of Cd exposure on tomato development, tolerance mechanisms, fruit quality and yield of tomato, as well as Cd distribution in the plants. / O consumo de tomate (Solanum lycopersicum L.) tem aumentado a cada ano devido a atratividade dos frutos, suas diversas utilizações e efeitos benéficos para a saúde humana. No entanto, os frutos de tomate podem acumular uma concentração de cádmio (Cd) que excede o limiar de segurança para o consumo humano, mesmo quando as plantas são cultivadas em solo com níveis aceitáveis de Cd. Cádmio e um elemento não-essencial, extremamente perigoso para os sistemas biológicos, desencadeando varias doenças em seres humanos. Nas plantas, o Cd perturba a maquinaria antioxidante, altera o estado nutricional e prejudica a produção e /ou o particionamento de fotoassimilados, frequentemente reduzindo a produtividade e qualidade de frutos. No entanto, diferentes acessos de tomateiros podem apresentar contrastantes graus de tolerância a toxicidade gerada pela exposição ao Cd, como detectado em estudos anteriores de nosso grupo. O uso desses acessos e uma abordagem poderosa para identificar as estratégias empregadas pelas plantas para lidar com os desafios induzidos pelo Cd; e o conhecimento de tais estratégias pode ser potencialmente utilizado em programas biotecnológicos e de melhoramento genético. Deste modo, o conjunto de estudos que compõem a presente tese objetivou (i) identificar os principais mecanismos que suportam o grau de tolerância contrastante a toxicidade induzida por Cd em acessos de tomate após exposição a curto e longo prazos a este metal pesado; (ii) avaliar a relação entre o grau de tolerância e os atributos físico-químico de frutos oriundos de tomateiros cultivados em solo contendo Cd, e (iii) determinar os efeitos transgeracionais do estresse induzido por Cd. No primeiro experimento, nove acessos de tomateiro com graus variados de tolerância a exposição ao Cd, baseado na acumulação de biomassa, foram cultivados em solução hidropônica contendo 35 μM de CdCl2 durante 6 dias. O impedimento de elevada concentração de magnésio (Mg) em raízes foi identificado como possível estratégia da planta para mitigar a toxicidade de Cd, por meio da evitação da formação de pelos radiculares. Em relação ao modo de ação da toxicidade induzida por Cd, o excesso de Mn, em adição a elevada concentração de Cd, parece estar acoplado aos danos foliares que são acentuados ainda mais pelas altas concentrações de zinco (Zn) e boro (B) nos tecidos fotossintéticos de plantas sob exposição ao Cd. No segundo experimento, os genótipos tolerantes (Yoshimatsu) e sensíveis (Tropic Two Orders) foram cultivados em solo contendo Cd, a fim de avaliar os parâmetros de produção. O genótipo tolerante apresentou frutos com maior diâmetro, altura e peso após o cultivo em solo contendo Cd, quando comparado as plantas controle. Em ambas as cultivares, a concentração de Cd variou de acordo com a seguinte ordem descendente: raízes = folíolos> (receptáculo floral, pedúnculo e sépalas) > caule = casca de fruta = polpa de fruta. Alem disso, dados sugerem que o receptáculo floral e suas estruturas atuaram como uma barreira ao transporte de Cd para os frutos, entretanto, ela não foi suficiente para evitar que o Cd atingisse os frutos. Em adição, a exposição ao Cd provocou notáveis reduções na concentração de Mg nas raízes de genótipos sensíveis e tolerantes, revelando que a aclimatação das plantas depende do baixo status de Mg em tecidos radiculares. Desde que ambas as cultivares são capazes de empregar este mecanismo, os dados sugerem que, durante a exposição a curto prazo ao Cd, acessos tolerantes são capazes de ativa-lo ou mais cedo ou mais rápido do que acessos sensíveis. Ademais, efeitos transgeracionais positivos na germinação e vigor das sementes do genótipo tolerante foram desencadeados pelo cultivo planta-mãe em solo com Cd, apesar do aumento de anormalidades cromossômicas. Este trabalho reportou novos conhecimentos sobre os efeitos da exposição ao Cd sobre o desenvolvimento do tomateiro, mecanismos de tolerância, qualidade e rendimento de frutos, bem como a distribuição de Cd dentro da planta.

Tomato (Solanum lycopersicum L.) consumption has increased every year due to the fruit attractiveness, several utilizations, and beneficial effects for human health. However, tomato fruits can accumulate a Cd concentration that exceeds the safety threshold for human consumption of vegetables, even when plants are grown in soil with acceptable Cd level. Cd is a non-essential, hazardous element to biological systems, triggering several diseases in humans. In plants, Cd disturbs the antioxidant machinery, changes the nutritional status, and impairs the photoassimilate production and/or partitioning, hence reducing fruit yield and quality. However, distinct tomato accessions can present contrasting tolerance degree to Cd toxicity, as detected by our group in previous studies. The use of these accessions is a powerful approach to identify strategies employed by plants to cope with Cdinduced challenges, and the acknowledgement of such strategies can be potentially used in breeding and biotechnological programs to improve fruit yield and quality in crops that were cultivated in contaminated fields. The set of studies that compose the present thesis aimed (i) to identify the main mechanisms for the contrasting tolerance degree to Cd-induced toxicity in tomato accessions after short and long-term Cd exposure; (ii) to evaluate the relationship among tolerance degree and fruits attributes in plants that were grown in Cd-containing soil, and (iii) to determine the transgenerational effects of Cd-induced stress. In the first experiment, nine tomato accessions with a varied tolerance degree, which was based on biomass accumulation, to Cd exposure were grown in hydroponic solution containing CdCl2 35 μM for 6 days. Avoidance of high Mg concentration in roots was identified as a plant strategy to mitigate Cd toxicity by preventing formation of root hairs. Regarding the mode of action of Cd toxicity, Mn excess in leaves, in addition to the high Cd concentration per se, seems to be coupled to leaf damages that are enhanced by the increased Zn and B concentrations in the photosynthetic tissues. In the second experiment, tolerant (Yoshimatsu) and sensitive (Tropic Two Orders) genotypes were grown in Cd-containing soil, in order to evaluated production parameters. After plant exposure to Cd, the tolerant genotype presented an increased fruit diameter, height and weight, when compared to the control plants. In both cultivars, Cd concentration varied according to the following descending order: roots = leaf blade > (floral receptacle, peduncle and sepals) > stem = fruit peel = fruit pulp. Moreover, data suggested that floral receptacle and its related-structures acted as a barrier to the Cd transportation to the fruits, but it was not enough to avoid Cd reaching the fruits. Furthermore, Cd exposure provoked remarkable reductions in the Mg concentration in roots of sensitive and tolerant genotypes, revealing that both tomato cultivars are able to employ this mechanism for plant acclimation to long-term Cd exposure. Considering such information, it is possible that, under the short-term Cd exposure, tolerant accessions activate this mechanism either early or faster than sensitive genotypes. In addition, positive transgenerational effects on seed germination and vigor of the tolerant genotype were triggered by the plant-mother cultivation in Cd-containing media, despite of the increased chromosomal abnormality. This work reported new insights about the effects of Cd exposure on tomato development, tolerance mechanisms, fruit quality and yield of tomato, as well as Cd distribution in the plants. / O consumo de tomate (Solanum lycopersicum L.) tem aumentado a cada ano devido a atratividade dos frutos, suas diversas utilizações e efeitos benéficos para a saúde humana. No entanto, os frutos de tomate podem acumular uma concentração de cádmio (Cd) que excede o limiar de segurança para o consumo humano, mesmo quando as plantas são cultivadas em solo com níveis aceitáveis de Cd. Cádmio e um elemento não-essencial, extremamente perigoso para os sistemas biológicos, desencadeando varias doenças em seres humanos. Nas plantas, o Cd perturba a maquinaria antioxidante, altera o estado nutricional e prejudica a produção e /ou o particionamento de fotoassimilados, frequentemente reduzindo a produtividade e qualidade de frutos. No entanto, diferentes acessos de tomateiros podem apresentar contrastantes graus de tolerância a toxicidade gerada pela exposição ao Cd, como detectado em estudos anteriores de nosso grupo. O uso desses acessos e uma abordagem poderosa para identificar as estratégias empregadas pelas plantas para lidar com os desafios induzidos pelo Cd; e o conhecimento de tais estratégias pode ser potencialmente utilizado em programas biotecnológicos e de melhoramento genético. Deste modo, o conjunto de estudos que compõem a presente tese objetivou (i) identificar os principais mecanismos que suportam o grau de tolerância contrastante a toxicidade induzida por Cd em acessos de tomate após exposição a curto e longo prazos a este metal pesado; (ii) avaliar a relação entre o grau de tolerância e os atributos físico-químico de frutos oriundos de tomateiros cultivados em solo contendo Cd, e (iii) determinar os efeitos transgeracionais do estresse induzido por Cd. No primeiro experimento, nove acessos de tomateiro com graus variados de tolerância a exposição ao Cd, baseado na acumulação de biomassa, foram cultivados em solução hidropônica contendo 35 μM de CdCl2 durante 6 dias. O impedimento de elevada concentração de magnésio (Mg) em raízes foi identificado como possível estratégia da planta para mitigar a toxicidade de Cd, por meio da evitação da formação de pelos radiculares. Em relação ao modo de ação da toxicidade induzida por Cd, o excesso de Mn, em adição a elevada concentração de Cd, parece estar acoplado aos danos foliares que são acentuados ainda mais pelas altas concentrações de zinco (Zn) e boro (B) nos tecidos fotossintéticos de plantas sob exposição ao Cd. No segundo experimento, os genótipos tolerantes (Yoshimatsu) e sensíveis (Tropic Two Orders) foram cultivados em solo contendo Cd, a fim de avaliar os parâmetros de produção. O genótipo tolerante apresentou frutos com maior diâmetro, altura e peso após o cultivo em solo contendo Cd, quando comparado as plantas controle. Em ambas as cultivares, a concentração de Cd variou de acordo com a seguinte ordem descendente: raízes = folíolos> (receptáculo floral, pedúnculo e sépalas) > caule = casca de fruta = polpa de fruta. Alem disso, dados sugerem que o receptáculo floral e suas estruturas atuaram como uma barreira ao transporte de Cd para os frutos, entretanto, ela não foi suficiente para evitar que o Cd atingisse os frutos. Em adição, a exposição ao Cd provocou notáveis reduções na concentração de Mg nas raízes de genótipos sensíveis e tolerantes, revelando que a aclimatação das plantas depende do baixo status de Mg em tecidos radiculares. Desde que ambas as cultivares são capazes de empregar este mecanismo, os dados sugerem que, durante a exposição a curto prazo ao Cd, acessos tolerantes são capazes de ativa-lo ou mais cedo ou mais rápido do que acessos sensíveis. Ademais, efeitos transgeracionais positivos na germinação e vigor das sementes do genótipo tolerante foram desencadeados pelo cultivo planta-mãe em solo com Cd, apesar do aumento de anormalidades cromossômicas. Este trabalho reportou novos conhecimentos sobre os efeitos da exposição ao Cd sobre o desenvolvimento do tomateiro, mecanismos de tolerância, qualidade e rendimento de frutos, bem como a distribuição de Cd dentro da planta.