A clock regulatory module is required for salt tolerance and control of heading date in rice

The circadian clock plays multiple roles in plant stress responses and developmental transition phases. Nevertheless, the underlying molecular mechanisms and individual clock components that coordinately regulate important agronomic traits of rice such as salt tolerance and heading date remain to be elucidated. Here, we identify a rice ternary repressive protein complex composed of OsELF4a, OsELF3-1 and OsLUX, which was designated as OsEC1 in analogy to a similar complex in Arabidopsis. OsELF4a physically interacts with OsELF3-1 and OsELF3-2 in nucleus, whilst OsELF3-1 rather than OsELF3-2 strongly interacts with OsLUX, a Myb-domain containing transcriptional factor. Phenotypic analyses show a role for this complex in heading and salt tolerance. The loss-of-function mutants of OsEC1 exhibit lower survival rate under salt stress and late heading date. Transcriptomic profiling together with biochemical assays identified the GIGANTEA homologue OsGI as a direct transcriptional target of OsEC1. Notably, the osgi-101 mutant, generated by CRISPR/Cas9, is salt tolerant and exhibits early heading date in long day conditions. Together, our findings characterized a transcriptional module in rice composed by the OsEC1 repressing OsGI, which links the circadian clock with salt tolerance and control of heading date.

Automated summary

This study identified a rice ternary repressive protein complex composed of OsELF4a, OsELF3-1, and OsLUX, which plays important roles in salt tolerance and heading in rice. Loss-of-function mutants of OsEC1 showed reduced survival rate under salt stress and late heading date. Transcriptomic profiling revealed that OsEC1 regulates salt tolerance and heading by repressing OsGI, a homologue of GIGANTEA.