The coordination of OsbZIP72 and OsMYBS2 with reverse roles regulates the transcription ofOsPsbS1in rice

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 ofPsbSin land plants. Here we demonstrated that the expression ofOsPsbS1is directly upregulated by OsbZIP72 while repressed by OsMYBS2 in rice. We identified a newcis-element GACAGGTG injaponica OsPsbS1promoter, to which OsbZIP72 could strongly bind and activate the expression ofOsPsbS1. The newcis-element CTAATC confers specific binding for OsMYBS2 injaponica OsPsbS1promoter. 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 ofOsPsbS1transcription under high light conditions inOsbZIP72knockout lines was greatly impaired, while the repression ofOsPsbS1transcription under a low light environment inOsMYBS2knockout 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.

Automated summary

In rice, OsPsbS1 expression is directly regulated by OsbZIP72 and inhibited by OsMYBS2, with new cis-elements GACAGGTG and CTAATC playing specific roles in the OsPsbS1 promoter. OsbZIP72 is regulated by SAPK1 and the ABA signaling pathway, while GF14A protein affects the repression activity of OsMYBS2 by regulating its nucleocytoplasmic shuttling.