Analysis of mutant showing abnormal response to light irradiation isolated from novel gain-of-function mutant lines for functional genomics in Arabidopsis

Abstract

We are establishing novel lines for functional genomics in Arabidopsis, in which each transcription factor ectopically is expressed. We have employed glucocorticoid receptor (GR)-mediated induction system to avoid lethality that may be caused by overexpression of transcription factors. We have isolated a mutant that has long hypocotyl phenotype and small cotyledons by application of dexamethasone (DEX) under long day condition. Interestingly, this long hypocotyl phenotype was observed on medium with low concentration but not high concentration of DEX. Oppositely, the phenotype of small cotyledons was dependent on the concentration of DEX. These phenotypes were observed under blue, red and far-red light conditions, but not under dark conditions. These results indicate that this mutant exhibits light dependent dwarfism. The gene encodes zinc finger type transcription factor, and the result of in vivo assay showed that this transcription factor is transcriptional repressor. We will discuss the functions of this transcription factor in light signal transductions.