Study On The Molecular Mechanism Of HOOKLESS1 Regulating The Flowering Time Of Arabidopsis

Flowering time is key during the transition from vegetative growth to reproductive growth in plants,and affects plant fitness and crop yields.FLOWERING LOCUS T(FT)is the longsought florigen,which determines plant floweing time.Transcription factor CONSTANS(CO)conveys photoperiod information and directly promotes FT transcription through binding to FT promoter.Blue light photoreceptor cryptochrome 2(CRY2)interacts with b HLH transcription factor CRY2-interacting b HLH 1(CIB1)to control flowering time,also through the regulation of FT transcription.Although the signaling mechanism underlying flowering time control has been extensively studied in the past decades,the detailed regulation on FT transcription is still not fully understood.HOOKLESS 1(HLS1)is a key regulatory factor in plant apical hook development.hls1 mutants fail to form apical hooks in etiolated seedlings.HLS1 controlls differential cell elongation through affecting the asymmetric distribution of auxin.HLS1 also converges multiple plant hormone signaling in the regulation of hook development.For example,ethylene treatment induces HLS1 expression,which promotes exaggerated apical hook formation.However,the biochemical function of HLS1 is still a mystery.We accidentally found that hls1 mutants displayed early flowering phenotypes,suggesting that HLS1 might participate in flowering time control.Further reporter gene expression and q RT-PCR assays showed that the spatial and temporal expression pattern of HLS1 overlapped with FT.Expression levels of FT were enhanced in hls1 mutants,which indiatced that HLS1 repressed FT transcription.HLS1 physically interacted with both CIB1 and CO,and suppressed their transcriptional activation on FT expression.Taken together,here we report that HLS1 is a new regulator to precisely control plant flowering time.