温敏两用核不育水稻株1S低起点育性转育温度的分子机理解析及应用

Hybrid rice, produced by crossings of male-sterile lines and restorer lines, has become the major planting type of rice production in China. The male-sterile line is the key determinator in both three- and two-line systems of rice hybrid breeding. Two-line system has a wide spectrum of restoration and can provide broader genetic resources for rice breeding to produce hybrids with strong hybrid vigor, thus becoming more and more favoring by breeders. However, the two-line breeding system is largely influenced by climate owing to its using photoperiod- or thermos-sensitive genic male sterility lines (P/TGMS) as maternal parents to produce hybrid seeds. Therefore, it is urgent to decrease the risk of hybrid rice breeding in the current climatic-condition with high frequency of extreme weather, which is important for ensuring the safety of grain production in China. Zhu1S is one of the widely used TGMS line with the critical temperature of sterility (CTS) around 22-23°C。We and collaborators previously cloned TMS5 controlling the TGMS of Zhu1S and AnnongS-1 (CTS around 26-27°C), respectively. However, the molecular mechanism underlying lower CTS of Zhu1S remains uncovered. In this proposal, we will clone the causal genes or QTL loci and then dissect their molecular mechanism in controlling lower CTS of Zhu1S using multiple biological methods. The marker-assistant selection or genome editing will be used to improve or breed TGMS with suitable CTS.

杂交水稻由雄性不育系与恢复系杂交获得，为我国水稻生产的主要类型。无论是生产杂交水稻的三系法还是两系法，雄性不育系均是实现育种的关键。两系法因配组自由，更利于选育出杂种优势强大的组合，越来越受到育种家的重视。然而两系法利用光温敏两用核不育系，制种易受气候条件影响。特别是当今极端天气频发，降低杂交水稻制种风险已成为保障我国粮食生产安全的迫切需求。株1S是目前生产上广泛应用的温敏两用核不育系，其转育起点温度为22-23°C，制种安全。我们及合作者前期克隆了控制株1S和安农S-1（转育起点温度26-27°C）的温敏不育基因TMS5，但调控株1S低起点转育温度的分子机制还不清楚。本项目拟采用遗传学、分子生物学和生物化学等多种研究手段，克隆控制株1S低起点转育温度的基因或QTL位点，并解析其分子机制。进而采用分子辅助或基因编辑手段，选育或创建转育温度适宜的两用不育系。

在两系杂交水稻生产中，低起点转育温度的温敏不育系是安全制种的关键。株1S是生产上广泛应用的温敏两用核不育系，转育起点温度为22-23°C，制种安全。我们及合作者前期克隆了控制株1S和安农S-1（转育起点温度26-27°C）的温敏不育基因TMS5，但调控株1S低起点转育温度的分子机制还不清楚。本研究通过对株1S和安农S-1的杂交配组和遗传分析，克隆了株1S低起点转育温度的控制基因。为两系杂交水稻安全制种所需的低起点温敏不育系快速、定向培育提供了关键基因资源。同时发现该基因的表达和DNA甲基化在株1S和安农S-1存在差异，暗示可能受表观遗传调控。为此我们建立了水稻定点去甲基化编辑体系，可特异去除靶位点DAN甲基化，产生可遗传的基因表达和农艺性状改变，为该基因的应用和作物遗传改良提供了新的工具。此外，通过对株1S诱变进行育性回复的高温抑制子筛选，获得了5个抑制子，克隆了2个控制株1S高温不育基因，并解析了其分别参与核糖体加工和核糖体翻译机器质量控制来调控株1S高温不育的分子机制，为株1S高温不育提供了理论基础。