RESUMO
In plants, light receptors play a pivotal role in photoperiod sensing, enabling them to track seasonal progression. Photoperiod sensing arises from an interaction between the plant's endogenous circadian oscillator and external light cues. Here, we characterize the role of phytochrome A (phyA) in photoperiod sensing. Our metaanalysis of functional genomic datasets identified phyA as a principal regulator of morning-activated genes, specifically in short photoperiods. We demonstrate that PHYA expression is under the direct control of the PHYTOCHROME INTERACTING FACTOR transcription factors, PIF4 and PIF5. As a result, phyA protein accumulates during the night, especially in short photoperiods. At dawn, phyA activation by light results in a burst of gene expression, with consequences for physiological processes such as anthocyanin accumulation. The combination of complex regulation of PHYA transcript and the unique molecular properties of phyA protein make this pathway a sensitive detector of both dawn and photoperiod.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Ritmo Circadiano , Fotoperíodo , Fitocromo A/metabolismo , Plantas Geneticamente Modificadas/metabolismo , Antocianinas/metabolismo , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Proteínas de Arabidopsis/genética , Regulação da Expressão Gênica de Plantas , Luz , Fitocromo A/genética , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/crescimento & desenvolvimentoAssuntos
Carbono/metabolismo , Fitocromo/metabolismo , Desenvolvimento Vegetal/fisiologia , Plantas/metabolismo , Transdução de Sinais/fisiologia , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Arabidopsis/efeitos da radiação , Biomassa , Luz , Fotossíntese/efeitos da radiação , Desenvolvimento Vegetal/efeitos da radiação , Plantas/efeitos da radiação , Transdução de Sinais/efeitos da radiaçãoRESUMO
MYB transcription factor genes play important roles in developmental and various other processes in plants. In this study, functional characterization of AmMYB1, a single-repeat MYB transcription factor isolated from the salt-tolerant mangrove tree Avicennia marina is reported. AmMYB1 cDNA was 1046 bp in length with an open reading frame of 783 bp, encoding 260 amino acids. The corresponding gene had two introns and three exons and was present as a single copy in A. marina. The deduced amino acid sequence showed similarities to MYB proteins reported in other plants, including the conserved MYB binding domain. RNA gel blot analysis showed that the AmMYB1 transcript expression was more pronounced in green photosynthetic tissue and was strongly induced by stresses such as salt (500 mM), light (500 µE m(-2) s(-1)), and the exogenous application of ABA (100 µM). An analysis of the upstream sequence of AmMYB1 gene revealed the presence of regulatory elements identical to those present in the promoters of stress inducible genes. The promoter was responsive to NaCl and could enhance reporter gene expression in planta. An in vitro DNA binding assay using the promoter region (TGGTTAG) of the AtRD22 gene and a transactivation assay in yeast cells suggest the possibility of AmMYB1 protein regulating the expression of other genes during salt stress. Transgenic tobacco plants constitutively expressing the AmMYB1 transcription factor showed better tolerance to NaCl stress.
Assuntos
Avicennia/genética , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Nicotiana/fisiologia , Cloreto de Sódio/farmacologia , Fatores de Transcrição/metabolismo , Ácido Abscísico/farmacologia , Sequência de Aminoácidos , Avicennia/efeitos dos fármacos , Avicennia/fisiologia , Regulação da Expressão Gênica de Plantas/genética , Luz , Dados de Sequência Molecular , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/genética , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/genética , Raízes de Plantas/metabolismo , Raízes de Plantas/efeitos da radiação , Caules de Planta/efeitos dos fármacos , Caules de Planta/genética , Caules de Planta/metabolismo , Caules de Planta/efeitos da radiação , Plantas Geneticamente Modificadas , Regiões Promotoras Genéticas/genética , Estrutura Terciária de Proteína , Proteínas Recombinantes de Fusão , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Tolerância ao Sal , Plântula/efeitos dos fármacos , Plântula/genética , Plântula/metabolismo , Plântula/efeitos da radiação , Sementes/efeitos dos fármacos , Sementes/genética , Sementes/metabolismo , Sementes/efeitos da radiação , Alinhamento de Sequência , Estresse Fisiológico , Nicotiana/efeitos dos fármacos , Nicotiana/genética , Nicotiana/efeitos da radiação , Fatores de Transcrição/genética , Ativação TranscricionalRESUMO
Damaged DNA Binding protein 1 (DDB1)-CULLIN4 E3 ubiquitin ligase complexes have been implicated in diverse biological processes in a range of organisms. Arabidopsis thaliana encodes two homologs of DDB1, DDB1A, and DDB1B. In this study we use a viable partial loss of function allele of DDB1B, ddb1b-2, to examine genetic interactions with DDB1A, DET1 and COP1. Although the ddb1b-2 ddb1a double mutant is lethal, ddb1a ddb1b-2/+ and ddb1b-2 ddb1a/+ heterozygotes exhibit few developmental phenotypes but do exhibit decreased tolerance of ultraviolet light. In addition, germination in ddb1a and ddb1a ddb1b-2/+ was found to be sensitive to salt and mannitol, and both DDB1 single mutants as well as the heterozygotes exhibited heat sensitivity. DE-ETIOLATED1 (DET1) and CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1) are negative regulators of light development which interact with DDB1-CUL4 complexes. Although ddb1a strongly enhances det1 phenotypes in both dark- and light-grown seedlings, ddb1b-2 weakly enhanced the det1 short hypocotyl phenotype in the dark, as well as enhancing anthocyanin levels and suppressing the det1 low chlorophyll phenotype in light-grown seedlings. In adults, ddb1a suppresses det1 early flowering and enhances the det1 dwarf phenotype. A similar trend was observed in ddb1b-2 det1 double mutants, although the effects were smaller in magnitude. In cop1 mutants, ddb1b-2 enhanced the cop1-4 short hypocotyl phenotype in dark and light, enhanced anthocyanin levels in cop1-1 in the light, but had no effect in adults. Thus the requirement for DDB1B varies in the course of development, from COP1-specific effects in hypocotyls to DET1-specific in adults.