Environment-sensitive genic male sterility (EGMS) lines are used widely in two-line hybrid breeding in rice (Oryza sativa). At present, photoperiod-sensitive genic male sterility (PGMS) lines and thermo-sensitive genic male sterility (TGMS) lines are predominantly used in two-line hybrid rice, with humidity-sensitive genic male sterility (HGMS) lines rarely being reported. Here, it is shown that HUMIDITY-SENSITIVE GENIC MALE STERILITY 1 (HMS1), encoding a β-ketoacyl-CoA synthase, plays key roles in the biosynthesis of very-long-chain fatty acids (VLCFAs) and HGMS in rice. The hms1 mutant displayed decreased seed setting under low humidity, but normal seed setting under high humidity. HMS1 catalyzed the biosynthesis of the C26 and C28 VLCFAs, contributing to the formation of bacula and tryphine in the pollen wall, which protect the pollen from dehydration. Under low-humidity conditions, hms1 pollen showed poor adhesion and reduced germination on the stigmas, which could be rescued by increasing humidity. HMS1-INTERACTING PROTEIN (HMS1I) interacted with HMS1 to coregulate HGMS. Furthermore, both japonica and indica rice varieties with defective HMS1 exhibited HGMS, suggesting that hms1 potentially could be used in hybrid breeding. The results herein reveal the novel mechanism of VLCFA-mediated pollen wall formation, which protects pollen from low-humidity stress in rice, and has a potential use in hybrid crop breeding.

中文翻译：

---

HMS1与HMS1I相互作用，调节水稻中的长链脂肪酸生物合成和对湿度敏感的雄性不育。

对环境敏感的雄性不育（EGMS）品系广泛用于水稻（Oryza sativa）的两系杂交育种。目前，在两系杂交水稻中主要使用光周期敏感性雄性不育系（PGMS）和热敏感性雄性不育系（TGMS），很少报道对湿度敏感的雄性不育系（HGMS）。此处显示，编码β-酮酰基-CoA合酶的湿度敏感基因男性不育1（HMS1）在水稻的超长链脂肪酸（VLCFA）和HGMS的生物合成中起关键作用。hms1突变体在低湿度下显示出降低的结实，而在高湿度下显示出正常的结实。HMS1催化C26和C28 VLCFA的生物合成，有助于在花粉壁中形成小球菌和胰蛋白酶。保护花粉免于脱水。在低湿度条件下，hms1花粉显示出较差的附着力并减少了柱头上的发芽，这可以通过增加湿度来挽救。HMS1相互作用蛋白（HMS1I）与HMS1相互作用以整合HGMS。此外，HMS1缺陷的粳稻和in稻品种均表现出HGMS，这表明hms1潜在地可用于杂交育种。本文的结果揭示了VLCFA介导的花粉壁形成的新机制，其保护花粉免受水稻中的低湿胁迫，并且在杂交作物育种中具有潜在用途。此外，HMS1缺陷的粳稻和in稻品种均表现出HGMS，这表明hms1可以用于杂交育种。本文的结果揭示了VLCFA介导的花粉壁形成的新机制，其保护花粉免受水稻中的低湿胁迫，并且在杂交作物育种中具有潜在用途。此外，HMS1缺陷的粳稻和in稻品种均表现出HGMS，这表明hms1潜在地可用于杂交育种。本文的结果揭示了VLCFA介导的花粉壁形成的新机制，其保护花粉免受水稻中的低湿胁迫，并且在杂交作物育种中具有潜在用途。