The E3 ligase OsHel2 impedes readthrough of stalled mRNAs to regulate male fertility in thermosensitive genic male sterile rice

Abstract

Heterosis is extensively used in the 2-line hybrid breeding system. Photosensitive/thermosensitive genic male sterile (P/TGMS) lines are key components of 2-line hybrid rice, and TGMS lines containing tms5 have significantly advanced 2-line hybrid rice breeding. We cloned the TMS5 gene and found that TMS5 is a tRNA cyclic phosphatase that can remove 2',3'-cyclic phosphate (cP) from cP-ΔCCA-tRNAs for efficient repair to ensure maintenance of mature tRNA levels. tms5 mutation causes increased levels of cP-ΔCCA-tRNAs and reduced levels of mature tRNAs, leading to male sterility at restrictive temperatures. However, the regulatory network of tms5-mediated TGMS remains to be clarified. Here, we demonstrate that the E3 ligase OsHel2 cooperates with TMS5 to regulate TGMS at restrictive temperatures. Consistently, both the accumulation of cP-ΔCCA-tRNAs and the reduction in mature tRNAs in the tms5 mutant are largely recovered in the tms5 oshel2-1 mutant. A lesion in OsHel2 results in partial readthrough of the stalled sequences, thereby enabling evasion of ribosome-associated protein quality control (RQC) surveillance. Our findings reveal a mechanism by which OsHel2 impedes readthrough of stalled mRNA sequences to regulate male fertility in TGMS rice, providing a paradigm for investigating how disorders in components of the RQC pathway impair cellular functions and lead to diseases or defects in other organisms.