华南农业大学生命科学学院庄楚雄研究员课题组成功克隆了水稻光温敏核不育基因。2月21日生命科学杂志《Cell Research》在线报道了该研究成果。该项研究成果与近日报道的华中农业大学张启发研究团队对“农垦58S”该相同光敏不育基因克隆的成果代表了我国在杂交稻分子基础研究领域的重大突破。

利用光温敏不育系培育的两系杂交水稻免除了保持系，在不同的光温条件下既可以作为不育系与恢复系杂交制种，又可以自身繁殖，从而简化了繁种制种程序，降低了杂交种子生产成本。更重要的是，两系杂交稻的配组较自由，选配到优良组合的机率较高。因此，两系杂交育种是我国在水稻杂种优势利用的重大突破。目前，两系杂交稻育种主要利用温敏不育系。

“培矮64S”是由国家杂交水稻工程技术研究中心的罗孝和研究员以我国水稻育种专家石明松发现的光敏水稻品种“农垦58S”为供体，以“培矮64”为受体，以回交选育成新型水稻品种“培矮64S”。由于其广亲和性及良好的农艺性状，“培矮64S”已成为了推广面积最大的两系杂交稻不育系亲本。“培矮64”虽然由“农垦58S”转育而来，但它却表现出温敏不育特性而非光敏不育特性。这种特性差异来源于哪，是否由相同的基因控制，以及它们的分子调控机制有何异同等重要问题一直不清楚。

在国家重大基础研究计划（973）的支持下，该课题组经多年的研究发现，“培矮64S”温敏不育性主要受第12染色体的一个主效基因座p/tms12-1控制。p/tms12-1是一个非编码RNA基因，它的原始转录本经过至少2次加工产生一个小RNA。与正常水稻品种相比，温敏不育水稻在该小RNA序列内存在一个单碱基突变。研究结果进一步表明，“农垦58S”也具有相同的该突变基因，这个单碱基突变是在籼稻产生温敏不育性和在粳稻产生光敏不育性的共同原因。在正常水稻中，野生型P/TMS12-1的表达抑制了温敏或光敏不育的发生。而温敏和光敏不育水稻中，p/tms12-1的该突变影响了小RNA的表达水平及其可能与靶基因的互作能力而产生雄性不育。该成果在水稻中率先发现了一类新的小RNA作为水稻光温敏育性转换的重要调控因子。

论文摘要：

Photoperiod- and thermo-sensitive genic male sterility (PGMS and TGMS) are the core components for hybrid breeding in crops. Hybrid rice based on the two-line system using PGMS and TGMS lines has been successfully developed and applied widely in agriculture. However, the molecular mechanism underlying the control of PGMS and TGMS remains obscure. In this study, we mapped and cloned a major locus, p/tms12-1 (photo- or thermo-sensitive genic male sterility locus on chromosome 12), which confers PGMS in the japonica rice line Nongken 58S (NK58S) and TGMS in the indica rice line Peiai 64S (PA64S, derived from NK58S). A 2.4-kb DNA fragment containing the wild-type allele P/TMS12-1 was able to restore the pollen fertility of NK58S and PA64S plants in genetic complementation. P/TMS12-1 encodes a unique noncoding RNA, which produces a 21-nucleotide small RNA that we named osa-smR5864w. A substitution of C-to-G in p/tms12-1, the only polymorphism relative to P/TMS12-1, is present in the mutant small RNA, namely osa-smR5864m. Furthermore, overexpression of a 375-bp sequence of P/TMS12-1 in transgenic NK58S and PA64S plants also produced osa-smR5864w and restored pollen fertility. The small RNA was expressed preferentially in young panicles, but its expression was not markedly affected by different day lengths or temperatures. Our results reveal that the point mutation in p/tms12-1, which probably leads to a loss-of-function for osa-smR5864m, constitutes a common cause for PGMS and TGMS in the japonica and indica lines, respectively. Our findings thus suggest that this noncoding small RNA gene is an important regulator of male development controlled by cross-talk between the genetic networks and environmental conditions.

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