ADA2b acts to positively regulate blue light-mediated photomorphogenesis in Arabidopsis

Cryptochromes (CRYs) act as blue light photoreceptors to regulate various plant physiological processes including photomorphogenesis and repair of DNA double strand breaks (DSBs). ADA2b is a conserved transcription co -activator that is involved in multiple plant developmental processes. It is known that ADA2b interacts with CRYs to mediate blue light -promoted DSBs repair. Whether ADA2b may participate in CRYsmediated photomorphogenesis is unknown. Here we show that ADA2b acts to inhibit hypocotyl elongation and hypocotyl cell elongation in blue light. We found that the SWIRM domain -containing C -terminus mediates the blue light -dependent interaction of ADA2b with CRYs in blue light. Moreover, ADA2b and CRYs act to coregulate the expression of hypocotyl elongation -related genes in blue light. Based on previous studies and these results, we propose that ADA2b plays dual functions in blue light -mediated DNA damage repair and photomorphogenesis.