The transcriptional co-repressor SEED DORMANCY 4-LIKE(At SDR4L) promotes the embryonic-to-vegetative transition in Arabidopsis thaliana

Repression of embryonic traits during the seedto-seedling phase transition requires the inactivation of master transcription factors associated with embryogenesis.How the timing of such inactivation is controlled is unclear.Here,we report on a novel transcriptional corepressor,Arabidopsis thaliana SDR4 L,that forms a feedback inhibition loop with the master transcription factors LEC1 and ABI3 to repress embryonic traits post-imbibition.LEC1 and ABI3 regulate their own expression by inducing AtSDR4 L during mid to late embryogenesis.AtSDR4 L binds to sites upstream of LEC1 and ABI4,and these transcripts are upregulated in Atsdr4 l seedlings.Atsdr4 l seedlings phenocopy a LEC1 overexpressor.The embryonic traits of Atsdr4 l can be partially rescued by impairing LEC1 or ABI3.The penetrance and expressivity of the Atsdr4 l phenotypes depend on both developmental and external cues,demonstrating the importance of AtSDR4 L in seedling establishment under suboptimal conditions.