The coordination of OsbZIP72 and OsMYBS2 with reverse roles regulates the transcription of OsPsbS1 in rice.

Abstract

Nonphotochemical quenching (NPQ), an intricate photoprotective process, plays fundamental roles in maintaining plant fitness. The PsbS protein is essential for the rapid induction of NPQ, and acts in a dose-dependent manner in leaves. However, little information is known on the transcriptional control of PsbS in land plants. Here we demonstrated that the expression of OsPsbS1 is directly upregulated by OsbZIP72 while repressed by OsMYBS2 in rice. We identified a new cis-element GACAGGTG in japonica OsPsbS1 promoter, to which OsbZIP72 could strongly bind and activate the expression of OsPsbS1. The new cis-element CTAATC confers specific binding for OsMYBS2 in japonica OsPsbS1 promoter. OsbZIP72 can be activated by SAPK1, and acts depending on the abscisic acid (ABA) signalling pathway. GF14A protein affects the repression activity of OsMYBS2 by regulating its nucleocytoplasmic shuttling, and Ser53 is necessary for OsMYBS2 to be retained in the cytoplasm. The inducibility of OsPsbS1 transcription under high light conditions in OsbZIP72 knockout lines was greatly impaired, while the repression of OsPsbS1 transcription under a low light environment in OsMYBS2 knockout lines was significantly alleviated. These results reveal cross-talk among NPQ processes, the ABA signalling pathway and abiotic stress signalling. The elaborate mechanisms may help enhance photoprotection and improve photosynthesis in rice.