China National Center for Rice Improvement & State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China; Crop Breeding and Cultivation Research Institute, Shanghai Academy of Agricultural Sciences, Shanghai 201403, China.
China National Center for Rice Improvement & State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China; Xuzhou Institute of Agricultural Sciences, Xuzhou 221131, China.
Plant Sci. 2022 Nov;324:111446. doi: 10.1016/j.plantsci.2022.111446. Epub 2022 Aug 27.
Heading date is crucial for rice reproduction and the geographical expansion of cultivation. We fine-mapped qHD5 and identified LOC_Os05g03040, a gene that encodes an AP2 transcription factor, as the candidate gene of qHD5 in our previous study. In this article, using two near-isogenic lines NIL(BG1) and NIL(XLJ), which were derived from the progeny of the cross between BigGrain1 (BG1) and Xiaolijing (XLJ), we verified that LOC_Os05g03040 represses heading date in rice through genetic complementation and CRISPR/Cas9 gene-editing experiments. Complementary results showed that qHD5 is a semi-dominant gene and that the qHD5 and qHD5 alleles are both functional. The homozygous mutant line generated from knocking out qHD5 in NIL(XLJ) headed earlier than NIL(XLJ) under both short-day and long-day conditions. In addition, the homozygous mutant line of qHD5 in NIL(BG1) also headed slightly earlier than NIL(BG1). All of these results show that qHD5 represses the heading date in rice. Transient expression showed that the qHD5 protein localizes to the nucleus. Transactivation activity assays showed that the C-terminus is the critical site that affects self-activation in qHD5. qRT-PCR analysis revealed that qHD5 represses flowering by down-regulating Ehd2. qHD5 may have been selected during indica rice domestication.
穗期对于水稻繁殖和种植的地理扩张至关重要。在之前的研究中，我们精细定位了 qHD5，并鉴定出 LOC_Os05g03040 是编码 AP2 转录因子的候选基因。在本文中，我们利用两个近等基因系 NIL(BG1)和 NIL(XLJ)，它们是由 BigGrain1 (BG1)和 Xiaolijing (XLJ)杂交后代衍生而来的，通过遗传互补和 CRISPR/Cas9 基因编辑实验验证了 LOC_Os05g03040 通过抑制水稻抽穗期来发挥作用。互补结果表明，qHD5 是一个半显性基因，qHD5 和 qHD5 等位基因都是有功能的。在 NIL(XLJ)中敲除 qHD5 后产生的纯合突变体在短日和长日条件下均比 NIL(XLJ)更早抽穗。此外，在 NIL(BG1)中敲除 qHD5 的纯合突变体也比 NIL(BG1)更早抽穗。所有这些结果表明 qHD5 抑制了水稻的抽穗期。瞬时表达表明 qHD5 蛋白定位于细胞核。转激活活性测定表明，C 端是影响 qHD5 自我激活的关键位点。qRT-PCR 分析表明 qHD5 通过下调 Ehd2 来抑制开花。qHD5 可能在籼稻驯化过程中被选择。
