Developing foliar growth of ivy geraniums (Pelargonium peltatum) bleaches white after exposure to temperatures greater than 30°C. This study investigated chloroplast development in ivy geraniums under heat stress comparing a heat sensitive cultivar, Temprano™ Lavender, and a heat tolerant cultivar, Contessa™ Red. Using transmission electron microscopy and spectrophotometry, foliar bleaching under heat stress was found to be due to an absence of developed chloroplasts within the bleached new growth accompanied by lower chlorophyll content. To determine whether heat stress related foliar bleaching could be prevented, cytokinin and gibberellins were applied in combination, at different rates before, during or after a heat stress event. Applying 50 to 100 ppm gibberellins before heat stress reduced bleaching in new growth. Gibberellins applied at 50 ppm within a week of a heat stress event decreased bleaching. Net photosynthesis and chlorophyll fluorescence was greater in non-heat stressed plants than heat stressed plants.

The plant hormones gibberellins (GAs) regulate multiple processes of plant development. Most of this regulation occurs at the transcriptional level, through the activity of the DELLAs, which are nuclear-localized proteins subjected to GA-mediated proteolitic degradation. DELLAs are encoded by five genes, and genetic studies show that each DELLA displays specific, but also partially overlapping roles with respect to their paralogs. In this Thesis, we have addressed two issues: (1) the contribution of DELLA multiplication to the diversification of functions controlled by GAs; and (2) the identification of direct targets regulated by DELLAs in etiolated seedlings with special attention to those involved in differential growth processes. Using combinations of mutants and transgenic lines expressing two phylogenetically distant DELLA genes (RGA and RGL2), we have found that these two DELLA proteins can perform each other's role as long as they are expressed under the reciprocal promoters, indicating that DELLA subfunctionalization relies mainly on their differential expression patterns. To identify direct DELLA targets, we have performed transcriptomic analyses of dark-grown seedlings expressing an inducible version of gai-1, a stable, dominant allele of a DELLA gene. This approach rendered a list of over 150 genes differentially expressed after induction of gai-1. The presence of several auxin-related genes among the primary targets of DELLA proteins has allowed us to establish a new role for GAs in the modulation of hypocotyl gravitropism through the repression of IAA19/MASSUGU2 expression by DELLAs. Moreover, the repression of HOOKLESS1 and the auxin efflux carriers PIN3 and PIN7 by DELLAs, is proposed as the molecular mechanism to explain the already known physiological regulation of apical hook development by GAs. / Gallego Bartolomé, J. (2011). Della protein function during differential growth processes in arabidopsis [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/11403

Las Giberelinas (GAs) intervienen en la regulación de numerosos procesos en el desarrollo a lo largo de la vida de la planta, y lo hacen promoviendo la degradación de las proteínas DELLA (DELLAs) [1], reguladoras negativas de las respuestas a GAs. Las DELLAs son nucleares y carecen de sitios de unión a DNA, sin embargo son capaces de interaccionar con otras proteínas y de esta manera regular la expresión génica [2-6]. Una de las preguntas que se abordaran en este proyecto es el de entender como las GAs son capaces de regular diversos procesos del crecimiento y del desarrollo, nuestra hipótesis se basa en que las proteínas DELLA se encuentran reprimiendo o potenciando la actividad de otras proteínas involucradas en diferentes procesos del desarrollo. / Marín De La Rosa, NA. (2014). DELLA proteins as hubs in signaling networks in plants [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/37193

Seed development, germination and dormancy, considered as the most important phenomena in seeds, are regulated by several plant hormones; gibberellin (GA) and abscisic acid (ABA) being the major players acting antagonistically. The regulation of these seed related processes by GA and ABA is dependent partly on the endogenous levels of the two hormones, which in turn are determined by the balance between their biosynthesis and catabolism. This thesis investigated the spatial and temporal expression patterns of several members of the GA and ABA biosynthetic and catabolic gene families during grain development using a non-dormant cultivar and during imbibition using grains collected from dormant and non-dormant cultivars of barley. In addition, the thesis examined the effect of exogenous ABA treatment, and after-ripening of seeds collected from dormant cultivars on the expression patterns GA and ABA metabolism genes during grain development and imbibition, respectively. The results suggest that specific members of the gene families related to the metabolic pathways of the two hormones exhibit distinct spatial and temporal roles in the regulation of barley grain development, dormancy and germination. / October 2015

Diversos estudos elucidaram mecanismos envolvidos com a organogênese in vitro, porém pouco é conhecido a respeito da fase de aquisição de competência, fundamental para que a regeneração ocorra. Alguns genes já foram identificados por interferirem na fase de aquisição de competência em tomateiro (Solanum lycopersicum), mas ainda existem diversas lacunas a serem esclarecidas. Para investigar a expressão de genes e o controle hormonal na fase de aquisição de competência, foram utilizados os mutantes de tomateiro, sob o background genético da cultivar Micro-Tom (MT), MT-Rg1 e MT-pro (procera), os quais afetam positiva ou negativamente a organogênese in vitro, respectivamente. Embora a resposta constitutiva a giberelina no mutante MT-pro seja conhecida, a identidade molecular do gene RG1 permanece indefinida. O mutante MT-Rg1 apresenta aumento tanto na formação de gemas caulinares quanto de raízes e reduz o tempo necessário para a indução desses órgãos, devido à diminuição do período para a aquisição de competência. A partir do estabelecimento das fases de aquisição de competência e indução da organogênese in vitro para MT e MT-Rg1, foram identificados genes diferencialmente expressos entre estes genótipos. Entre estes genes, CELL DIVISION CYCLE ASSOCIATED 7 e LACCASE 1A estão regulados positivamente em MT-Rg1 e todos estão fortemente relacionados à fase de aquisição de competência, e a alterações na proliferação de células do protoxilema durante o início da organogênese. Por outro lado, a resposta constitutiva à giberelina no mutante MT-pro reduz a formação de gemas caulinares e raízes e aumenta a formação de calos in vitro, sem afetar o tempo requerido para a indução de gemas caulinares e raízes. De forma oposta a MT-Rg1, o gene CDCA7 apresenta expressão reduzida durante a fase de aquisição de competência em MT-pro, diminuindo o número de células do protoxilema em divisão. Outro fator importante para a divisão celular no mutante MT-pro é o aumento da expressão do gene WUS, causando um aumento da proliferação das stem cells, que são células indiferenciadas relacionadas à formação de novos órgãos. Esta proliferação celular inadequada, somada a uma alteração desfavorável na homeostase das citocininas, justifica o efeito negativo do alelo pro na formação de gemas caulinares, o que permitiu a criação de um novo modelo para organogênese in vitro / Several studies have enabled the discovery of mechanisms to achieve in vitro organogenesis; however, little is known about the phase of acquisition of competence, essential for regeneration. A few genes have been identified to interfere in the acquisition of the competence phase in tomato (Solanum lycopersicum), but there are still many gaps to be filled. We have used the mutants, under the genetic background of the Micro-Tom cultivar, MT-Rg1 and MT-pro (procera), which positively or negatively affect in vitro organogenesis, respectively, to investigate gene expression and the hormonal control in the phase of acquisition of competence. Despite the fact that the constitutive gibberellin response in the procera mutant is well-established, the molecular identity of RG1 gene remains unknown. The MT-Rg1 mutant presents an increase in the formation of both shoot and roots and a reduced period for the induction of these organs, because of the reduced time required for acquisition of competence.We searched for the identity of differentially expressed genes between MT and MT-Rg1 after the establishment of the competence acquisition phase and organogenesis induction stages. Among those genes, CDCA7 and LAC1A are upregulated in MT-Rg1 and these genes appear to be strongly related with the acquisition of competence phase and changes in proliferation of protoxylem cells during early organogenesis. The constitutive response to gibberellin in the MT-pro mutant decreases the formation of shoot and roots and increase in vitro calli formation, without reducing the induction phase of shoots and roots. Unlike MT-Rg1, MT-pro reduces the CDCA7L expression during the acquisition of competence phase, causing a reduction of the protoxylem dividing cells. Another important factor for cell division in MT-pro mutant is the increased expression of the WUS gene, leading to an abnormal proliferation of stem cells. Thereby, this abnormal cell proliferation, in addition to an unfavorable change in the cytokinin homeostasis, justify the negative effect of the pro allele in the shoot formation, which enabled the proposal of a new model for in vitro organogenesis

Many characteristics of a fully developed fruit are controlled by processes that take place early in fruit development, even at floral meristem level. In fact, events that range from the transition of a vegetative into an inflorescence meristem to the last stages of fruit ripening determine characteristics of a mature fruit. Transcription factors post-transcriptionally regulated by microRNAs (miRNAs) play crucial roles in most of these stages. In such pathways, miRNAs may regulate its targets spatially, temporally, or dampen amount of targets transcript to provide optimal expression patterns for adequate organ development. Many miRNAs have been described to be essential in the regulation of flowering time, gynoecium patterning, post-pollination gynoecium growth and fruit ripening, among other stages of fruit development. Some aspects of early stages of gynoecium development, such as floral meristem maintenance, carpel fusion and gynoecium pattern, have been well studied in Arabidopsis. However, these stages are poorly understood in the development of fleshy fruit species, such as tomato. Many miRNA-related pathways were described to interact with phytohormone pathways. A good example is the interaction between miR156 and Gibberellins (GA) in the regulation of flowering time. Interestingly, this interaction is substantially different in Arabidopsis and tomato. MiR156 have been also shown to have distinct roles in controlling tomato and Arabidopsis gynoecium development. Considering this, here we: (1) review the available literature concerning control of fruit development, from gynoecium patterning to fruit ripening, by non-coding RNAs and (2) study the relationship between miR156 and GA pathways in the regulation of early stages of fruit development. We show that these pathways control floral meristem size and boundary establishment during gynoecium development and miR156 pathway modulates responses to GA. / Muitas características finais deu um fruto são controladas por processos que se dão muito cedo no desenvolvimento dos frutos, até mesmo a nível de meristema. De fato, processos que vão desde a transição de um meristema vegetativo para um meristema de inflorescência até os estágios finais do amadurecimento definem muitas características do fruto maduro. Fatores de transcrição regulados pós transcricionalmente por microRNAs (miRNAs) têm papel crucial na maior parte desses estágios. Nessas vias os miRNAs geralmente regulam a expressão de seus alvos espacialmente, temporalmente, ou diminuem o acúmulo de transcritos do alvo, proporcionando níveis adequados de expressão para o desenvolvimento do órgão. Muitos estudos mostram que determinados miRNAs são essenciais no controle do tempo de florescimento, desenvolvimento do gineceu, crescimento do fruto após a polinização e amadurecimento, dentre outros estágios do desenvolvimento do fruto. Muitos aspectos do controle do desenvolvimento inicial do gineceu foram relativamente bem estudados em Arabidopsis. Porém, essas etapas iniciais do desenvolvimento de carpelos/gineceu ainda não são bem estudadas em plantas que produzem fruto carnoso, como é o caso do tomateiro. Já foi demonstrado que muitas vias reguladas por miRNAs interagem com fitormônios na regulação de vários processos de desenvolvimento. Como exemplo podemos citar a relação entre a via do miR156 e a via das giberelinas (GA) no controle do tempo de florescimento. Essa relação é substancialmente em Arabidopsis e tomateiro. Além disso, foi demonstrado que o miR156 possui papéis distintos na regulação do desenvolvimento do gineceu nessas duas espécies. Dessa forma, nesse trabalho nós: (1) fazemos uma revisão de literatura sobre a regulação do desenvolvimento de frutos, do desenvolvimento inicial do gineceu ao amadurecimento, por vias reguladas por RNAs não codantes e; (2) estudamos a relação entre as vias do miR156 e GA na regulação de etapas iniciais do desenvolvimento de frutos. Nós demonstramos que essas vivas controlam o tamanho de meristemas florais, bem como o estabelecimento de zonas de divisão no desenvolvimento do gineceu. Além disso, mostramos que a via do miR156 modula a resposta a GA.

No description available.

Lodging is a key agronomic problem in E. tef. due to morpho-physiological features, such tall and slender phenotype of the plant. Gibberellins metabolic genes are key targets in the control of plant height. Plant growth regulators (PGRs) that inhibit GA biosynthesis are used to shorten stem length thereby increasing lodging resistance. E. tef responded to treatment with PGRs such as GA, chlormequat chloride (CCC) and paclobutrazol (PBZ). Both PGRs reduced E. tef plant height but CCC treatment did not affect grain yield. Stem diameter was not affected by PGR treatment and also not the poor tapering (acropitally increasing diameter). Putatively transformed E. tef plants carrying a bean GA 2-oxidase (PcGA2ox) coding sequence were further produced via embryogenic callus after Agrobacterium-mediated transformation and plants were successfully grown into mature fertile plants. Eight putative transformed plants were finally generated carrying the insert (PcGA20 ox or nptII gene sequence) at the T0 generation. Constitutive expression of the GA 2-oxidase (PcGA2ox) coding sequence in E. tef resulted in phenotypic changes such as reduction in culm height, change in biomass, reduction in amount of GA in putative transformant semi-dwarf plants. The challenges found in the transgene detection in the T1 generation has been highlighted. Pheno-morphic changes occurred with little or no effect on yield. Genes involved in height control (orthologs to the rice sd-1 gene) and signaling (Rht) in E. tef were also identified and characterized. Activity of the protein for the putative rice sd-1 orthologs was further confirmed by heterologous expression. The three putative sequences in E. tef were named EtGA20ox1a, EtGA20ox1b and EtGA20ox2. Expression analysis showed that EtGA20ox2 were much less transcribed compared to the others and EtGA20ox1b could be the functional equivalent to the rice sd-1 (OsGA20ox2) gene in E. tef. Further, E. tef mutants with a semi-dwarf phenotype could be developed through mutagenesis and TILLING. However, regardless of height, grain yield was severely reduced in all mutants except in the semi-dwarf mutant GA-10. This line also had significantly higher diameter in most internodes which might contribute to the stiffness of stem. G-10 is therefore a promising line for further investigations. / Thesis (PhD)--University of Pretoria, 2012. / Plant Science / unrestricted

Diversos estudos elucidaram mecanismos envolvidos com a organogênese in vitro, porém pouco é conhecido a respeito da fase de aquisição de competência, fundamental para que a regeneração ocorra. Alguns genes já foram identificados por interferirem na fase de aquisição de competência em tomateiro (Solanum lycopersicum), mas ainda existem diversas lacunas a serem esclarecidas. Para investigar a expressão de genes e o controle hormonal na fase de aquisição de competência, foram utilizados os mutantes de tomateiro, sob o background genético da cultivar Micro-Tom (MT), MT-Rg1 e MT-pro (procera), os quais afetam positiva ou negativamente a organogênese in vitro, respectivamente. Embora a resposta constitutiva a giberelina no mutante MT-pro seja conhecida, a identidade molecular do gene RG1 permanece indefinida. O mutante MT-Rg1 apresenta aumento tanto na formação de gemas caulinares quanto de raízes e reduz o tempo necessário para a indução desses órgãos, devido à diminuição do período para a aquisição de competência. A partir do estabelecimento das fases de aquisição de competência e indução da organogênese in vitro para MT e MT-Rg1, foram identificados genes diferencialmente expressos entre estes genótipos. Entre estes genes, CELL DIVISION CYCLE ASSOCIATED 7 e LACCASE 1A estão regulados positivamente em MT-Rg1 e todos estão fortemente relacionados à fase de aquisição de competência, e a alterações na proliferação de células do protoxilema durante o início da organogênese. Por outro lado, a resposta constitutiva à giberelina no mutante MT-pro reduz a formação de gemas caulinares e raízes e aumenta a formação de calos in vitro, sem afetar o tempo requerido para a indução de gemas caulinares e raízes. De forma oposta a MT-Rg1, o gene CDCA7 apresenta expressão reduzida durante a fase de aquisição de competência em MT-pro, diminuindo o número de células do protoxilema em divisão. Outro fator importante para a divisão celular no mutante MT-pro é o aumento da expressão do gene WUS, causando um aumento da proliferação das stem cells, que são células indiferenciadas relacionadas à formação de novos órgãos. Esta proliferação celular inadequada, somada a uma alteração desfavorável na homeostase das citocininas, justifica o efeito negativo do alelo pro na formação de gemas caulinares, o que permitiu a criação de um novo modelo para organogênese in vitro / Several studies have enabled the discovery of mechanisms to achieve in vitro organogenesis; however, little is known about the phase of acquisition of competence, essential for regeneration. A few genes have been identified to interfere in the acquisition of the competence phase in tomato (Solanum lycopersicum), but there are still many gaps to be filled. We have used the mutants, under the genetic background of the Micro-Tom cultivar, MT-Rg1 and MT-pro (procera), which positively or negatively affect in vitro organogenesis, respectively, to investigate gene expression and the hormonal control in the phase of acquisition of competence. Despite the fact that the constitutive gibberellin response in the procera mutant is well-established, the molecular identity of RG1 gene remains unknown. The MT-Rg1 mutant presents an increase in the formation of both shoot and roots and a reduced period for the induction of these organs, because of the reduced time required for acquisition of competence.We searched for the identity of differentially expressed genes between MT and MT-Rg1 after the establishment of the competence acquisition phase and organogenesis induction stages. Among those genes, CDCA7 and LAC1A are upregulated in MT-Rg1 and these genes appear to be strongly related with the acquisition of competence phase and changes in proliferation of protoxylem cells during early organogenesis. The constitutive response to gibberellin in the MT-pro mutant decreases the formation of shoot and roots and increase in vitro calli formation, without reducing the induction phase of shoots and roots. Unlike MT-Rg1, MT-pro reduces the CDCA7L expression during the acquisition of competence phase, causing a reduction of the protoxylem dividing cells. Another important factor for cell division in MT-pro mutant is the increased expression of the WUS gene, leading to an abnormal proliferation of stem cells. Thereby, this abnormal cell proliferation, in addition to an unfavorable change in the cytokinin homeostasis, justify the negative effect of the pro allele in the shoot formation, which enabled the proposal of a new model for in vitro organogenesis

No description available.