Roles of OsSOQ1 in photoprotection and fatty acid metabolism of rice

Abstract

Presented here is the function analysis of a homolog of Arabidopsis SOQ1, OsSOQ1 in rice. Homozygous mutants (ossoq1) were obtained by CRISPR/Cas9 to knockout OsSOQ1. The mutants showed significant lower plant height, tiller number, panicle length, effective panicle, and grain number per panicle compared to the wild-type (WT). Western blot analysis showed that OsSOQ1 is a thylakoid membrane protein, with the thioredoxin-like (Trx-like) domain facing the lumen. Loss of OsSOQ1 did not significantly affect the protein level of photosystem II (PSII) subunits, but down-regulated the content of a non-photochemical quenching (NPQ) player PsbS, resulting in a low NPQ under high light intensity in the mutant. UPLC-MS/MS experiments showed that OsSOQ1 is involved in the fatty acid biosynthesis pathway of rice. The Trx-like domain possessed redox activity in vitro as shown by insulin assay; and in the yeast two-hybrid experiment, it was found that the Trx-like domain interacted with the chloroplast lipocalin OsLCNP, which usually binds lipid molecules. These findings revealed that the role of OsSOQ1 is to maintain the photochemical efficiency of PSII under high light intensity and regulate fatty acid metabolism in rice.