ABSTRACT
BACKGROUND: Arabidopsis ZBF1/MYC2bHLH transcription factor is a repressor of photomorphogenesis, and acts as a point of cross talk in light, abscisic acid (ABA) and jasmonic acid (JA) signaling pathways. MYC2 also functions as a positive regulator of lateral root development and flowering time under long day conditions. However, the function of MYC2 in growth and development remains unknown in crop plants. RESULTS: Here, we report the functional analyses of LeMYC2 in tomato (Lycopersicon esculentum). The amino acid sequence of LeMYC2 showed extensive homology with Arabidopsis MYC2, containing the conserved bHLH domain. To study the function of LeMYC2 in tomato, overexpression and RNA interference (RNAi) LeMYC2 tomato transgenic plants were generated. Examination of seedling morphology, physiological responses and light regulated gene expression has revealed that LeMYC2 works as a negative regulator of blue light mediated photomorphogenesis. Furthermore, LeMYC2 specifically binds to the G-box of LeRBCS-3A promoter. Overexpression of LeMYC2 has led to increased root length with more number of lateral roots. The tomato plants overexpressing LeMYC2 have reduced internode distance with more branches, and display the opposite morphology to RNAi transgenic lines. Furthermore, this study shows that LeMYC2 promotes ABA and JA responsiveness. CONCLUSIONS: Collectively, this study highlights that working in light, ABA and JA signaling pathways LeMYC2 works as an important regulator for growth and development in tomato plants.
Subject(s)
Light , Solanum lycopersicum/growth & development , Solanum lycopersicum/metabolism , Abscisic Acid/metabolism , Arabidopsis Proteins/genetics , Arabidopsis Proteins/metabolism , Cyclopentanes/metabolism , Gene Expression Regulation, Plant/genetics , Gene Expression Regulation, Plant/radiation effects , Solanum lycopersicum/genetics , Solanum lycopersicum/radiation effects , Oxylipins/metabolism , Signal Transduction/genetics , Signal Transduction/radiation effectsABSTRACT
Arabidopsis HY1/HO1, heme oxygenase enzyme, catalyses the oxygenation of heme to produce biliverdin, an essential step in the phytochrome-chromophore biosynthesis pathway. GBF1/ZBF2 is a G/Z-box binding bZIP protein that plays a dual but opposite regulatory roles in blue light-mediated seedling development and gene expression. Here, we show the genetic interactions of HY1 and GBF1 in seedling photomorphogenesis, and the role of HY1 in the regulation of promoters containing the Z-box light responsive element. Our results indicate that whereas the additional mutation in GBF1 does not affect the phenotype of hy1 mutant seedlings in red or far-red light, the additional mutation in HY1 suppresses the hyper photomorphogenic phenotype of gbf1 in BL. Further, transgenic studies using promoter-reporter constructs indicate that functional HY1 is essential for the optimal induction of Z-box containing synthetic and native promoters at various stages of Arabidopsis growth and development. Thus, this study establishes a functional relation of HY1 with GBF1, and HY1-mediated regulation of Z-box containing promoters in Arabidopsis seedling development.
Subject(s)
Arabidopsis Proteins/genetics , Arabidopsis/genetics , Gene Expression Regulation, Plant , Oxidoreductases/genetics , Transcription Factors/genetics , Arabidopsis/growth & development , Arabidopsis/metabolism , Arabidopsis Proteins/metabolism , Light , Mutation , Oxidoreductases/metabolism , Phenotype , Promoter Regions, Genetic , Seedlings/genetics , Seedlings/growth & development , Seedlings/metabolism , Signal Transduction , Transcription Factors/metabolismABSTRACT
MYC2 is a basic helix-loop-helix transcription factor that cross talks with light, abscisic acid (ABA), and jasmonic acid (JA) signaling pathways. Here, we have shown that Arabidopsis (Arabidopsis thaliana) MYC2 directly binds to the G-box present in the SUPPRESSOR OF PHYTOCHROME A1 (SPA1) promoter and that it controls the expression of SPA1 in a COP1-dependent manner. Analyses of atmyc2 spa1 double mutants suggest that whereas MYC2 and SPA1 act redundantly to suppress photomorphogenic growth in the dark, they function synergistically for the suppression of photomorphogenic growth in the light. Our studies have also revealed that MYC2-mediated ABA and JA responses are further modulated by SPA1. Taken together, this study demonstrates the molecular and physiological interrelations of MYC2 and SPA1 in light, ABA, and JA signaling pathways.
