Monsanto Company, St. Louis, Missouri, United States of America.
PLoS One. 2018 Aug 23;13(8):e0202921. doi: 10.1371/journal.pone.0202921. eCollection 2018.
Hybrid crops produce higher yields than their inbred parents due to heterosis. For high purity of hybrid seeds, it is critical to eliminate self-pollination. Manual or mechanical removal of male parts (such as detasseling in maize) is labor-intensive, fuel and time-consuming, and can cause physical damage to female plants, resulting in significant seed yield reductions. Many male-sterility systems either require a maintainer for male-sterile line propagation or are often affected by environmental factors. Roundup® Hybridization System (RHS) utilizes glyphosate to induce male sterility, which effectively eliminates the need for maintainer lines and removal of male parts for commercial hybrid seed production. The first-generation RHS (RHS1) is based on low expression of a glyphosate-insensitive 5-enolpyruvylshikimate-3-phosphate synthase (CP4 EPSPS) in pollen. This report presents the second-generation RHS (RHS2) technology built on RNA interference (RNAi) combined with CP4 EPSPS. It utilizes maize endogenous male tissue-specific small interfering RNAs (mts-siRNAs) to trigger cleavage of the CP4 EPSPS mRNA specifically in tassels, resulting in glyphosate-sensitive male cells due to lack of the CP4 EPSPS protein. Male sterility is then induced by glyphosate application at the stages critical for pollen development, and the male-sterile plants are used as the female parent to produce hybrid seed. The endogenous mts-siRNAs are conserved across maize germplasms, and the inducible male sterility was replicated in representative germplasms through introgression of a CP4 EPSPS transgene containing the mts-siRNA target sequence. This technology combines the relative simplicity and convenience of a systemic herbicide spray methodology with targeted protein expression to create an inducible male sterility system for industrial production of row crop hybrid seeds in an environmentally-independent manner.
杂种作物由于杂种优势，比其自交亲本产生更高的产量。为了获得高纯度的杂交种子，消除自花授粉至关重要。手动或机械去除雄性部分（如玉米的去雄）是劳动密集型的，耗费燃料和时间，并且会对雌性植物造成物理损伤，导致种子产量显著降低。许多雄性不育系统要么需要雄性不育系繁殖的保持系，要么经常受到环境因素的影响。Roundup® Hybridization System（RHS）利用草甘膦诱导雄性不育，有效地消除了对保持系的需求以及去除雄性部分以用于商业杂交种子生产。第一代 RHS（RHS1）基于花粉中草甘膦不敏感的 5-烯醇丙酮酰莽草酸-3-磷酸合酶（CP4 EPSPS）的低表达。本报告介绍了第二代 RHS（RHS2）技术，该技术基于 RNA 干扰（RNAi）与 CP4 EPSPS 的结合。它利用玉米内源雄性组织特异性小干扰 RNA（mts-siRNA）来特异性切割 tassels 中的 CP4 EPSPS mRNA，导致由于缺乏 CP4 EPSPS 蛋白，草甘膦敏感的雄性细胞。然后，在花粉发育关键阶段应用草甘膦诱导雄性不育，并用雄性不育植物作为母本生产杂交种子。内源 mts-siRNA 在玉米种质资源中是保守的，通过含有 mts-siRNA 靶序列的 CP4 EPSPS 转基因的导入，在代表性种质资源中复制了可诱导的雄性不育。该技术将系统除草剂喷雾方法的相对简单性和便利性与靶向蛋白表达相结合，为以环境独立的方式在工业上生产行播作物杂交种子创建了一个可诱导的雄性不育系统。
