State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Sciences, South China Agricultural University, Guangzhou, China.
Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing, China.
J Exp Bot. 2018 Mar 24;69(7):1533-1543. doi: 10.1093/jxb/ery017.
Plant architecture is a major target of rice (Oryza sativa) breeding and selection, but the underlying regulatory networks remain unclear. Here, we overexpressed an OsNAC2 mutant (OErN) that cannot be cleaved by the miRNA miR164b. OErN plants had better plant architecture and longer panicles, and produced more grains. The parental line averaged 12.2 primary and 31.5 secondary branches in the main panicles; two OErN lines averaged 15.0 and 15.2 primary, and 41.5 and 44.3 secondary branches. In large-scale field trials, OErN plants produced at least 58.62% more total grain (by weight) compared with the parental line. They also had more large and small vascular bundles in the stem internodes and leaves. Overexpression of miR164b or down-regulation of OsNAC2 led to decreased panicle length and grain yield in the main panicle. The OErN plants showed significant up-regulation of the grain number and plant architecture-related genes IPA1 and DEP1. A survey of >3000 rice varieties found no natural mutations in the miR164b-binding site of OsNAC2. OErN increased yield in Nipponbare and the commonly grown Yangyujing 3 cultivars. In summary, we identified an efficient new strategy to increase rice yield substantially and improve plant architecture through overexpression of OsmiR164b-resistant OsNAC2.
植物结构是水稻（Oryza sativa）育种和选择的主要目标，但基础调控网络仍不清楚。在这里，我们过表达了一个不能被 miRNA miR164b 切割的 OsNAC2 突变体（OErN）。OErN 植株具有更好的植物结构和更长的穗，并且产生更多的谷物。亲本系主穗上平均有 12.2 个一级和 31.5 个二级分枝；两个 OErN 系平均有 15.0 和 15.2 个一级，和 41.5 和 44.3 个二级分枝。在大规模田间试验中，OErN 植株的总谷物产量（按重量计）比亲本系至少增加了 58.62%。它们在茎节和叶片中的大、小维管束也更多。miR164b 的过表达或 OsNAC2 的下调导致主穗上的穗长和谷物产量减少。OErN 植株显著上调了与谷物数量和植物结构相关的 IPA1 和 DEP1 基因。对 >3000 个水稻品种的调查发现，OsNAC2 的 miR164b 结合位点没有自然突变。OErN 增加了 Nipponbare 和广泛种植的 Yangyujing 3 品种的产量。总之，我们通过过表达抗 miR164b 的 OsNAC2，鉴定出一种有效提高水稻产量和改善植物结构的新策略。
