Ornithine δ-aminotransferase OsOAT is critical for male fertility and cold tolerance during rice plant development.

Cold stress is a major factor limiting the production and geographical distribution of rice (Oryza sativa) varieties. However, the molecular mechanisms underlying cold tolerance remain to be elucidated. Here, we report that ornithine δ-aminotransferase (OsOAT) contributes to cold tolerance during the vegetative and reproductive development of rice. osoat mutant was identified as a temperature-sensitive male sterile mutant with deformed floral organs and seedlings sensitive to cold stress. Comparative transcriptome analysis showed that OsOAT mutation and cold treatment of the wild-type plant led to similar changes in the global gene expression profiles in anthers. OsOAT genes in indica rice Huanghuazhan (HHZ) and japonica rice Wuyungeng (WYG) are different in gene structure and response to cold. OsOAT is cold-inducible in WYG but cold-irresponsive in HHZ. Further studies showed that indica varieties carry both WYG-type and HHZ-type OsOAT, whereas japonica varieties mostly carry WYG-type OsOAT. Cultivars carrying HHZ-type OsOAT are mainly distributed in low-latitude regions, whereas varieties carrying WYG-type OsOAT are distributed in both low- and high-latitude regions. Moreover, indica varieties carrying WYG-type OsOAT generally have higher seed-setting rates than those carrying HHZ-type OsOAT under cold stress at reproductive stage, highlighting the favorable selection for WYG-type OsOAT during domestication and breeding to cope with low temperatures.