The ability of plants to not only detect but also adjust to their environment is crucial for their survival. The genes involved in photomorphogenesis – developmental changes in response to light – and their regulation have long been of interest to researchers. While the phytochrome and cryptochrome photoreceptors have been isolated and partially characterized, the downstream components of the light signaling pathway which transmit the perceived light signals and regulate gene expression are still being discovered. A negative regulator of photomorphogenesis, DET1 (de-etiolated 1), was discovered in a mutant screen for plants that develop a light grown phenotype in the dark. DET1 is nuclear localized, but its exact function remains unknown. Two contrasting mechanisms for the role of DET1 in the regulation of gene expression have been proposed based on studies of the tomato and human orthologs of DET1. In order to reveal the mechanism and molecular context of DET1 action, suppressor mutant screens were employed to discover additional genes acting in conjunction with DET1 (designated as TED genes). In this research, new genomic methods were developed and employed to identify the genes underlying the ted1-1SD and ted2-1D suppressor mutations. A long hypocotyl QTL and suppression of the det1-1 dark grown phenotype by the Bensheim (Be-0) ecotype of Arabidopsis mapped to the HAT4 gene, a homeoboxdomain leucine-zipper transcription factor involved in shade-avoidance responses. Sequence analysis uncovered two functionally distinct alleles of HAT4 in the Be-0 alleles of HAT4 compared to the genomic standard Columbia (Col-0) ecotype. Expression analysis showed that in addition to negative autoregulation by itself, HAT4 is also negatively regulated by DET1. The ted2-1D mutation was mapped to a 57 Kbp interval on chromosome I containing three likely candidate genes. Suppression of the det1-1 phenotype by ted2-1D is overdominant which is highly unusual and typically associated with hybrid vigor or heterosis traits. The discovery of the genes underlying the ted1-1SD and ted2-1D suppressor mutations have furthered the understanding of the role for DET1 in regulation of photomorphogenesis as well as mechanisms involved in overall gene regulation during light signaling.

Methyl bromide fumigation, a common method used to combat soil borne pathogens in commercial tomato cultivation, was to be limited by the Montreal Protocol due to concerns of ozone depletion. Alternative methods to protect tomatoes against diseases include grafting. However, short grafted transplants may expose the scion to the soil. To avoid scion exposure, hypocotyl elongation of two tomato rootstocks 'Maxifort' and 'Aloha' via end-of-day far-red (EOD-FR) was examined in terms of light quality (red to far-red ratio, or R/FR) and dose (product of far-red intensity and duration). In EOD-FR light quality experiments, 'Aloha' seedlings were exposed to unfiltered and filtered incandescent light with an R/FR of 0.5 and 0.05 respectively. The resulting hypocotyl elongation was higher in filtered light than either the unfiltered light or the untreated control. Hypocotyl elongation response to EOD-FR dose in 'Aloha' and 'Maxifort' was affected by both far-red intensity and treatment duration. A saturating response was also found within a far-red dose between 0–8 mmol•m⁻²•d⁻¹ and modeled using non-linear regression with a three parameter Michaelis-Menten equation to estimate the far-red dose required to obtain near-maximum hypocotyl elongation for 'Aloha' and 'Maxifort'. The far-red dose required was affected by cultivar and experimental period. None of the EOD-FR treatments affected plant mass or stem diameter. To conclude, for maximum hypocotyl elongation using EOD-FR, the lower R/FR would increase the effectiveness of the treatment. The far-red dose should preferably be at 4–8 mmol• m⁻²•d⁻¹.

Mutants showing developmental hyper-responsiveness to limited light were screened and designated as seedlings hyper-responsive to light (shl). These mutants showed an etiolated phenotype similar to wild type in the dark, yet had shorter hypocotyls, larger cotyledons, and more advanced development of true leaves than wild type in low light. The SHL genes act (genetically) as light-dependent negative regulators of photomorphogenesis, possibly in a downstream signaling or developmental pathway that is shared by the major photoreceptor genes (CRY1, PHYA, and PHYB) and other photoreceptors (CRY2, PHYC, PHYD, and PHYE). shl1 and shl2 were shown to be partially dependent on HY5 activity for their light-hyperresponsive phenotypes. shl1-1 showed a defect in responding to auxin in its root development in both white and yellow light conditions, and showed a defect in responding to auxin in hypocotyl elongation in yellow light. Compared to wild type, both shl1-1 and shl2-2 showed increased hypocotyl length in response to cytokinin in white light. Gibberellin (GA) partially recovered shl1-1 mutant phenotype in yellow light, whereas showed no effect on hypocotyl elongation of shl2-2 in this light condition. These altered responses of shl1-1 and shl2-2 to multiple phytohormones in different light regimes suggests that cross-talks among light and hormones regulate SHL1 and SHL2. One of the SHL genes, SHL2 was cloned by map-based positional cloning and shown to be allelic to the previously identified locus designated murus3(mur3) and katamari1(kam1). MUR3/KAM1 encodes a XyG galactosyltransferase. Sequence analysis demonstrated that our original EMS generated reference allele shl2-2 is probably not a null mutant, therefore the phenotypes of T-DNA insertion null mutant in SHL2, SALK_074435 were studied in different light conditions. Unlike shl2-2, SALK_074435 had a slightly short hypocotyl phenotype in the dark (though not to the extent of the det/cop/fus mutants). A consideration of the phenotypes and molecular lesions of shl2-2 and mur3 alleles, along with the phenotypes of null alleles kam1 and SALK_74435, suggests that SHL2/MUR3/KAM1 may be involved in hypocotyl elongation in low light through the modification of xyloglucan in the plant cell wall, and may play a role in hypocotyl elongation in the dark through proper organization of the endomembrane.

The peculiarities of gravisensing of hypocotyls and roots of the same seedling for the first time were compared under different gravistimulation conditions. Indirect experimental method, i.e. quantitative analysis of the dependence of amyloplast statics and kinetics on the direction and magnitude of gravitational force, was applied to assess the cytoskeleton role in the maintenance of polarized root and hypocotyl statocyte structure and amyloplast movements during seedling gravistimulation. The experiments were performed with garden cress (Lepidium sativum L.) seedlings in the dark by using original devices ‒ in-flight centrifuge ‘Neris-5’ (biosatellite ‘Bion-10’) in space and centrifuge-clinostat (a device with two orthogonal axes) in the Earth for modelling of altered gravity and gravitropic stimulation conditions. The magnitude of the gravitational force was changed from microgravity (real in space or simulated by horizontal clinostat) to 1-g (simulated by centrifugation in space or natural Earth's gravity) and its action direction was changed at 90° or 180° inversion with respect to the longitudinal axis of the seedlings. It was determined that the action of gravitational force is not an essential factor for the formation of gravisensing tissues in hypocotyl and root of garden cress seedlings; however, under real and simulated microgravity the growth of endodermal cells in hypocotyls is slower, the location of amyloplasts changes significantly with respect to the... [to full text] / Pirmą kartą buvo palyginti to paties daigo šaknies ir hipokotilio gravitacijos jutimo savitumai skirtingomis gravitacinio dirginimo sąlygomis. Netiesioginiu eksperimentiniu metodu, t.y. kiekybiškai analizuojant amiloplastų statikos ir kinetikos priklausomybę nuo gravitacinės jėgos veikimo krypties ir dydžio, buvo įvertinta citoskeleto reikšmė poliarizuotos šaknų ir hipokotilių statocitų struktūros palaikymui ir viduląsteliniams amiloplastų judesiams daigų gravitacinio dirginimo metu. Eksperimentai atlikti su sėjamosios pipirnės (Lepidium sativum L.) daigais tamsoje, gravitacijos pokyčių generavimui naudojant originalius prietaisus – borto centrifugą „Neris-5“ kosminio skrydžio sąlygomis (biopalydovas „Bion-10“) ir dviejų ortogonalių ašių centrifugą-klinostatą. Gravitacinės jėgos dydis buvo keičiamas nuo mikrogravitacijos lygmens (reali kosmose arba imituota horizontaliu klinostatavimu) iki 1 g (imituota centrifugavimu arba natūrali Žemės gravitacija), o jos veikimo kryptis buvo keičiama 90° arba 180° kampu daigo išilginės ašies atžvilgiu. Nustatyta, kad gravitacinės jėgos buvimas nėra būtina sąlyga sėjamosios pipirnės daigų šaknų ir hipokotilių gravisensorinio audinio formavimuisi, bet jai neveikiant (reali ir imituota mikrogravitacija) sulėtėja hipokotilių endodermio ląstelių augimas, pakinta gravisensorinių ląstelių poliškumas dėl esminio amiloplastų pakilimo ląstelių centro kryptimi. Nuolatinio gravitropinio dirginimo metu, kuomet sėjamosios pipirnės daigus šaknies... [toliau žr. visą tekstą]

Pirmą kartą buvo palyginti to paties daigo šaknies ir hipokotilio gravitacijos jutimo savitumai skirtingomis gravitacinio dirginimo sąlygomis. Netiesioginiu eksperimentiniu metodu, t.y. kiekybiškai analizuojant amiloplastų statikos ir kinetikos priklausomybę nuo gravitacinės jėgos veikimo krypties ir dydžio, buvo įvertinta citoskeleto reikšmė poliarizuotos šaknų ir hipokotilių statocitų struktūros palaikymui ir viduląsteliniams amiloplastų judesiams daigų gravitacinio dirginimo metu. Eksperimentai atlikti su sėjamosios pipirnės (Lepidium sativum L.) daigais tamsoje, gravitacijos pokyčių generavimui naudojant originalius prietaisus – borto centrifugą „Neris-5“ kosminio skrydžio sąlygomis (biopalydovas „Bion-10“) ir dviejų ortogonalių ašių centrifugą-klinostatą. Gravitacinės jėgos dydis buvo keičiamas nuo mikrogravitacijos lygmens (reali kosmose arba imituota horizontaliu klinostatavimu) iki 1 g (imituota centrifugavimu arba natūrali Žemės gravitacija), o jos veikimo kryptis buvo keičiama 90° arba 180° kampu daigo išilginės ašies atžvilgiu. Nustatyta, kad gravitacinės jėgos buvimas nėra būtina sąlyga sėjamosios pipirnės daigų šaknų ir hipokotilių gravisensorinio audinio formavimuisi, bet jai neveikiant (reali ir imituota mikrogravitacija) sulėtėja hipokotilių endodermio ląstelių augimas, pakinta gravisensorinių ląstelių poliškumas dėl esminio amiloplastų pakilimo ląstelių centro kryptimi. Nuolatinio gravitropinio dirginimo metu, kuomet sėjamosios pipirnės daigus šaknies... [toliau žr. visą tekstą] / The peculiarities of gravisensing of hypocotyls and roots of the same seedling for the first time were compared under different gravistimulation conditions. Indirect experimental method, i.e. quantitative analysis of the dependence of amyloplast statics and kinetics on the direction and magnitude of gravitational force, was applied to assess the cytoskeleton role in the maintenance of polarized root and hypocotyl statocyte structure and amyloplast movements during seedling gravistimulation. The experiments were performed with garden cress (Lepidium sativum L.) seedlings in the dark by using original devices ‒ in-flight centrifuge ‘Neris-5’ (biosatellite ‘Bion-10’) in space and centrifuge-clinostat (a device with two orthogonal axes) in the Earth for modelling of altered gravity and gravitropic stimulation conditions. The magnitude of the gravitational force was changed from microgravity (real in space or simulated by horizontal clinostat) to 1-g (simulated by centrifugation in space or natural Earth's gravity) and its action direction was changed at 90° or 180° inversion with respect to the longitudinal axis of the seedlings. It was determined that the action of gravitational force is not an essential factor for the formation of gravisensing tissues in hypocotyl and root of garden cress seedlings; however, under real and simulated microgravity the growth of endodermal cells in hypocotyls is slower, the location of amyloplasts changes significantly with respect to the... [to full text]

ABA insensitive mutants (abi1 - abi5) have been isolated in germination screens that use high concentrations of exogenous ABA, and this method is believed to be saturated. To overcome this problem, a sensitized screen that used much lower concentration of exogenous ABA was performed to isolate new ABA insensitive mutants. Some of the isolated mutants had defects in light or retrograde signalling. One particular mutant (18-11) developed long hypocotyls under normal light condition. Based on its response to blue, red and far-red light conditions, this mutant is likely a novel hy mutant. Genetic analysis revealed that while ABA insensitivity in this mutant is recessive, the long hypocotyl phenotype is dominant. Positional cloning is currently being carried out to identify the gene. Findings from this study supports that ABA signalling interacts with light signalling networks.

ABA insensitive mutants (abi1 - abi5) have been isolated in germination screens that use high concentrations of exogenous ABA, and this method is believed to be saturated. To overcome this problem, a sensitized screen that used much lower concentration of exogenous ABA was performed to isolate new ABA insensitive mutants. Some of the isolated mutants had defects in light or retrograde signalling. One particular mutant (18-11) developed long hypocotyls under normal light condition. Based on its response to blue, red and far-red light conditions, this mutant is likely a novel hy mutant. Genetic analysis revealed that while ABA insensitivity in this mutant is recessive, the long hypocotyl phenotype is dominant. Positional cloning is currently being carried out to identify the gene. Findings from this study supports that ABA signalling interacts with light signalling networks.

L’auxine est une hormone fondamentale dans le développement et la physiologie de la plante. L’obtention des plantes conditionnelles pour ABP1 a permis la mise en évidence de son importance dans la signalisation de l’auxine. Ainsi ABP1 agirait d’une part sur l’endocytose de vésicules à clathrine au niveau de la membrane plasmique et d’autre part sur la stabilité des Aux/IAAs. Ce dernier résultat suggère qu’une voie de signalisation en aval d’ABP1 permet de modifier l’homéostasie de la voie de régulation transcriptionnelle de l’auxine, la voie SCFTIR/AFBs.Mon travail de thèse a consisté à caractériser les plantes inactivées pour ABP1 lors de la croissance à l’obscurité dans la plante modèle Arabidopsis thaliana. Mon étude montre qu’ABP1 contrôle l’expansion cellulaire en jouant sur la plasticité pariétale. J’ai ainsi pu mettre en évidence une modification de la proportion de formes fucosylées des chaînes latérales des xyloglucanes, le principal hémicellulose de la paroi primaire chez Arabidopsis. Cette modification de la fucosylation des xyloglucanes requiert des changements d’expressions géniques médiés ce qui conforte l’existence d’une voie de signalisation reliant ABP1 à la voie SCFTIR/AFBs.En parallèle, j’ai mené une approche génétique de recherche de suppresseurs du phénotype lié à l’inactivation d’ABP1 à l’obscurité. Parmi les dix lignées validées, j’ai d’ores et déjà identifié le gène DCL3 comme étant impliqué dans la suppression du phénotype ss12k et mis en évidence l’implication de la voie d’extinction de gènes par l’intermédiaire de petits ARNs non codant (voie RdDM) dans le contrôle de l’expansion cellulaire. / Auxin is a key hormone concerning the control of plant physiology and the impact on plant development. Conditional plants for ABP1 allowed the post embryonic studies and have contributed to demonstrate the involvement of ABP1 in a broad range of cellular and developmental responses including the clathrin-dependent endocytosis and the regulation of Aux/IAAs homeostasis. These datas revealed that an ABP1-dependent pathway is acting on transcriptional regulation by modulating the SCFTIR/AFBs signaling pathway. I took advantage of the phenotype of dark grown seedlings to study cell expansion in ABP1 loss of function background. ABP1 knockdown induced modifications of fucosylated form of xyloglucan side chains that are the main hemicellulose in Arabidopsis primary cell wall. All data converge to show that this effect results from alterations of expression of cell wall related genes via the modulation of the SCFTIR/AFBs pathway. In parallel, I used a suppressor approach to discover new signaling components downstream of ABP1. Characterisation of one of the suppressor leads to the identification of a loss of function allele of DCL3. This data demonstrates the involvement of the RNA directed DNA methylation pathway downstream of ABP1.

Muitas respostas moduladas pela luz durante o desenvolvimento das plantas também são reguladas por hormônios vegetais, levando à hipótese da interação entre ambos os fatores. Uma ferramenta valiosa para testar tal interação seria o uso de mutantes fotomorfogenéticos e hormonais, bem como duplos mutantes combinando ambos. Em tomateiro, embora sejam disponíveis mutantes com alterações na biossíntese de fotorreceptores e/ou na transdução do sinal da luz, bem como mutantes no metabolismo e/ou sensibilidade hormonal, esses estão presentes em cultivares diferentes, o que pode limitar seu uso de modo integrado e a construção de duplos mutantes. No presente trabalho, foram introgredidas em uma única cultivar de tomateiro, Micro-Tom (cv. MT), dezenove mutações afetando a biossíntese ou a resposta a fitocromo, bem como aos hormônios auxina (AUX), citocinina (CK), giberelina (GA), ácido abscísico (ABA), etileno (ET) e brassinoesteróides (BR). Tomando-se vantagem de tal coleção, duas respostas notadamente controladas tanto pela luz quanto por hormônios foram estudadas: alongamento e acúmulo de antocianinas em hipocótilos. Para tal, foram utilizadas as seguintes abordagens: i) tratamentos exógenos de diferentes classes hormonais em mutantes fotomorfogenéticos, ii) observação de hipocótilos de mutantes hormonais crescidos na luz e no escuro, iii) observação de duplos mutantes combinando mutações hormonais e fotomorfogenéticas. Assim, o acúmulo de antocianinas foi promovido pela CK e ABA e inibido pela GA, concordando com a redução no mutante deficiente em ABA (notabilis ou not) e no mutante hipersensível à GA (procera ou pro). Apesar do mutante com baixa sensibilidade à AUX (diageotropica ou dgt) acumular exageradamente antocianinas, a aplicação exógena não evidenciou o papel da AUX, sendo, porém, coerente com a sugestão de que esse mutante possui um balanço AUX/CK voltado para CK. Tanto a aplicação exógena quanto a avaliação nos mutantes epinastic (epi), super produção de ET, e Never ripe (Nr), baixa sensibilidade ao ET, sugerem uma função limitada desse hormônio na biossíntese de antocianinas. Na luz e no escuro, AUX, CK, ABA e ET exógenos resultaram na inibição do alongamento do hipocótilo, sendo coerente com a promoção em dgt (luz), promoção em sit (luz), inibição em epi (luz e escuro). Por outro lado, GA promoveu o alongamento corroborando a promoção em pro. Contrariando o efeito exógeno da CK, brt reduziu o alongamento na luz e no escuro. No escuro, o único mutante que apresentou alongamento do hipocótilo superior a MT foi o mutante deficiente na biossíntese do phy (aurea ou au). A utilização de duplos mutantes combinando phy- e alterações hormonais mostrou uma interação aditiva (au epi, au Nr, au dgt e au sit), sinergística (au pro) e epinástica (au brt) no acúmulo de antocianinas e alongamento do hipocótilo na luz, porém nessa última resposta, au dgt e au sit indicaram uma interação sinergística. Juntos, esses resultados indicam que, embora phy possui vias distintas da AUX, ET, ABA e GA no controle do acúmulo de antocianinas e alongamento do hipocótilo, parece que esse fotorreceptor partilha vias comuns com CK em ambas as respostas. / Many responses regulated by light during plant development are also regulated by plant hormones, suggesting an interaction between these factors. One important approach to test this hypothesis is the use of photomorphogenic and hormonal mutants and double mutant analysis. Mutants with altered photoreceptor biosynthesis, light signal transduction, hormonal metabolism and hormonal sensitivity are available in tomato. However, since they are in different cultivars, this can be a limitation for their use in a comprehensive study, as well as, for the construction of double mutants. In this work we performed the introgression of nineteen mutations in a single cultivar of tomato, Micro- Tom (cv. MT). These mutations affect biosynthesis or response to phytochrome (phy), auxin (AUX), cytokinin (CK), gibberellin (GA), abscisic acid (ABA), ethylene (ET) and brassinosteroid (BR). Using this collection of hormone mutants, we studied two responses which are controlled by light and hormones: elongation and anthocyanin accumulation in hypocotyls. For this purpose, we used three approaches: i) hormonal treatment in the photomorphogenic mutants, ii) measurement of hypocotyl lengths from hormonal mutants grown under light and dark conditions and iii) double mutant (photomorphogenic-hormonal) analysis. Anthocyanin accumulation was promoted by CK and ABA and inhibited by GA. This is in accordance with the reduction of anthocyanin accumulation in the ABA deficient mutant (not) and in the GA hypersensitive mutant (pro). Although the diageotropica (dgt), auxin-insensitive mutant, showed a high anthocyanin accumulation, the addition of auxin did not supported a role for this hormone in anthocyanin accumulation. On the other hand, this could be due to a low auxin-tocytokinin ratio presented by dgt. Data from mutants with altered metabolism and sensitivity of ethylene, epinastic (epi) and Never ripe (Nr) respectively, and from plants treated with this hormone suggest a limited role of ethylene in the anthocyanin biosynthesis. Exogenous AUX, CK, ABA and ET inhibited the hypocotyl elongation. This is coherent with the promotion of hypocotyl elongation in dgt and sit mutants under light conditions and inhibition of hypocotyl elongation in the epi mutant in the light and dark. On the other hand, GA promoted the hypocotyl elongation corroborating the same effect seen in pro. The brt mutant showed a reduced hypocotyl elongation in light and dark conditions, which contradicts the effect of exogenous cytokinin. The phytochromedeficient aurea (au) mutant was the only one to show an enhanced hypocotyl elongation in the dark compared to the wild type (MT). The combination between photomorphogenic and hormonal mutants (double mutants) showed additive (au epi, au Nr, au dgt e au sit), synergistic (au pro) and epistatic (au brt) interactions considering the anthocyanin accumulation and hypocotyl elongation. Synergistic interaction was observed in the elongation hypocotyl of the au dgt and au sit double mutants. These results indicate that phy and CK may share some signaling/metabolic pathways in the control of anthocyanin accumulation and hypocotyl elongation. On the other hand, our data do not support an interaction between phy and the hormones AUX, ET, ABA and GA in the control of hypocotyls elongation or anthocyanin accumulation.

Muitas respostas moduladas pela luz durante o desenvolvimento das plantas também são reguladas por hormônios vegetais, levando à hipótese da interação entre ambos os fatores. Uma ferramenta valiosa para testar tal interação seria o uso de mutantes fotomorfogenéticos e hormonais, bem como duplos mutantes combinando ambos. Em tomateiro, embora sejam disponíveis mutantes com alterações na biossíntese de fotorreceptores e/ou na transdução do sinal da luz, bem como mutantes no metabolismo e/ou sensibilidade hormonal, esses estão presentes em cultivares diferentes, o que pode limitar seu uso de modo integrado e a construção de duplos mutantes. No presente trabalho, foram introgredidas em uma única cultivar de tomateiro, Micro-Tom (cv. MT), dezenove mutações afetando a biossíntese ou a resposta a fitocromo, bem como aos hormônios auxina (AUX), citocinina (CK), giberelina (GA), ácido abscísico (ABA), etileno (ET) e brassinoesteróides (BR). Tomando-se vantagem de tal coleção, duas respostas notadamente controladas tanto pela luz quanto por hormônios foram estudadas: alongamento e acúmulo de antocianinas em hipocótilos. Para tal, foram utilizadas as seguintes abordagens: i) tratamentos exógenos de diferentes classes hormonais em mutantes fotomorfogenéticos, ii) observação de hipocótilos de mutantes hormonais crescidos na luz e no escuro, iii) observação de duplos mutantes combinando mutações hormonais e fotomorfogenéticas. Assim, o acúmulo de antocianinas foi promovido pela CK e ABA e inibido pela GA, concordando com a redução no mutante deficiente em ABA (notabilis ou not) e no mutante hipersensível à GA (procera ou pro). Apesar do mutante com baixa sensibilidade à AUX (diageotropica ou dgt) acumular exageradamente antocianinas, a aplicação exógena não evidenciou o papel da AUX, sendo, porém, coerente com a sugestão de que esse mutante possui um balanço AUX/CK voltado para CK. Tanto a aplicação exógena quanto a avaliação nos mutantes epinastic (epi), super produção de ET, e Never ripe (Nr), baixa sensibilidade ao ET, sugerem uma função limitada desse hormônio na biossíntese de antocianinas. Na luz e no escuro, AUX, CK, ABA e ET exógenos resultaram na inibição do alongamento do hipocótilo, sendo coerente com a promoção em dgt (luz), promoção em sit (luz), inibição em epi (luz e escuro). Por outro lado, GA promoveu o alongamento corroborando a promoção em pro. Contrariando o efeito exógeno da CK, brt reduziu o alongamento na luz e no escuro. No escuro, o único mutante que apresentou alongamento do hipocótilo superior a MT foi o mutante deficiente na biossíntese do phy (aurea ou au). A utilização de duplos mutantes combinando phy- e alterações hormonais mostrou uma interação aditiva (au epi, au Nr, au dgt e au sit), sinergística (au pro) e epinástica (au brt) no acúmulo de antocianinas e alongamento do hipocótilo na luz, porém nessa última resposta, au dgt e au sit indicaram uma interação sinergística. Juntos, esses resultados indicam que, embora phy possui vias distintas da AUX, ET, ABA e GA no controle do acúmulo de antocianinas e alongamento do hipocótilo, parece que esse fotorreceptor partilha vias comuns com CK em ambas as respostas. / Many responses regulated by light during plant development are also regulated by plant hormones, suggesting an interaction between these factors. One important approach to test this hypothesis is the use of photomorphogenic and hormonal mutants and double mutant analysis. Mutants with altered photoreceptor biosynthesis, light signal transduction, hormonal metabolism and hormonal sensitivity are available in tomato. However, since they are in different cultivars, this can be a limitation for their use in a comprehensive study, as well as, for the construction of double mutants. In this work we performed the introgression of nineteen mutations in a single cultivar of tomato, Micro- Tom (cv. MT). These mutations affect biosynthesis or response to phytochrome (phy), auxin (AUX), cytokinin (CK), gibberellin (GA), abscisic acid (ABA), ethylene (ET) and brassinosteroid (BR). Using this collection of hormone mutants, we studied two responses which are controlled by light and hormones: elongation and anthocyanin accumulation in hypocotyls. For this purpose, we used three approaches: i) hormonal treatment in the photomorphogenic mutants, ii) measurement of hypocotyl lengths from hormonal mutants grown under light and dark conditions and iii) double mutant (photomorphogenic-hormonal) analysis. Anthocyanin accumulation was promoted by CK and ABA and inhibited by GA. This is in accordance with the reduction of anthocyanin accumulation in the ABA deficient mutant (not) and in the GA hypersensitive mutant (pro). Although the diageotropica (dgt), auxin-insensitive mutant, showed a high anthocyanin accumulation, the addition of auxin did not supported a role for this hormone in anthocyanin accumulation. On the other hand, this could be due to a low auxin-tocytokinin ratio presented by dgt. Data from mutants with altered metabolism and sensitivity of ethylene, epinastic (epi) and Never ripe (Nr) respectively, and from plants treated with this hormone suggest a limited role of ethylene in the anthocyanin biosynthesis. Exogenous AUX, CK, ABA and ET inhibited the hypocotyl elongation. This is coherent with the promotion of hypocotyl elongation in dgt and sit mutants under light conditions and inhibition of hypocotyl elongation in the epi mutant in the light and dark. On the other hand, GA promoted the hypocotyl elongation corroborating the same effect seen in pro. The brt mutant showed a reduced hypocotyl elongation in light and dark conditions, which contradicts the effect of exogenous cytokinin. The phytochromedeficient aurea (au) mutant was the only one to show an enhanced hypocotyl elongation in the dark compared to the wild type (MT). The combination between photomorphogenic and hormonal mutants (double mutants) showed additive (au epi, au Nr, au dgt e au sit), synergistic (au pro) and epistatic (au brt) interactions considering the anthocyanin accumulation and hypocotyl elongation. Synergistic interaction was observed in the elongation hypocotyl of the au dgt and au sit double mutants. These results indicate that phy and CK may share some signaling/metabolic pathways in the control of anthocyanin accumulation and hypocotyl elongation. On the other hand, our data do not support an interaction between phy and the hormones AUX, ET, ABA and GA in the control of hypocotyls elongation or anthocyanin accumulation.