Integration of Regulatory Information for Seed Storage Protein Gene Expression

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In this project, we conducted functional analysis of master regulatory transcription factors of seed maturation including VPl/ABI3, FUS3 and LEC1, and ABA responsive element (ABRE)-binding factor TIW31. Through such study, we tried to elucidate the molecular mechanisms underlying the intergration of regulatory information directing the seed-specific expression of seed storage protein genes.By utilizing artificial gene expression induction system with dexamethazone (dex) or estrogen (est), FUS3 or ABI3 was ectopically induced in vegetative tissues of transgenic Arabidopsis plants. As known for ABI3, ectopic expression of FUS3 resulted in the ectopic expression of seed storage protein genes in the presence of ABA. Detailed kinetic analyses of induction Cruciferin C (CRC) by FUS3 was found to be significantly slower than that by ABI3. This and other evidence suggested that ABA-dependent FUS3 induction of CRC was mediated by FUS3 and ABA-dependent synthesis of intermediate regulatory facto … More r (s) (most likely to be banscription factor (s)). Kinetic microarray analysis and cotransfection experiment with cultured cell protoplasts identified bZIP67 transcription factor as the strong candidate for such a intermediate transcription factor.From the analyses using transgeneic Arabidopsis capable of ectopically inducing LEC1, LEC1 regulation of seed storage protein genes was mediated by FUS3 and ABI3. This conclusion was obtained from the observation that ABI3 and FUS3 were induced by ectopic expression of LEC1 and that the LEC1 induction of CRC and At2S expression was significantly recuced in the abi3 or fus3 munatant background.We previously identified ABA-responsive element binding factor TRAB1 as a transcription factor that mediate ABA signal to activated transcription of ABA-regulated genes. In this study, we demonstrated that TRAB1 is activated by ABA-dependent phosphorylation of Serl02. Furhteromre, we identified three SnRK2 protein kinases as those responsible for ABA-dependent phosphorylation of TRAB1. Less