Xu Fan, Tang Jiuyou, Wang Shengxing, Cheng Xi, Wang Hongru, Ou Shujun, Gao Shaopei, Li Boshu, Qian Yangwen, Gao Caixia, Chu Chengcai
State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, China.
Key Laboratory of Biotechnology and Crop Quality Improvement, Ministry of Agriculture/Biotechnology Research Center, Southwest University, Chongqing, China.
Nat Genet. 2022 Dec;54(12):1972-1982. doi: 10.1038/s41588-022-01240-7. Epub 2022 Dec 5.
Preharvest sprouting (PHS) due to lack of seed dormancy seriously threatens crop production worldwide. As a complex quantitative trait, breeding of crop cultivars with suitable seed dormancy is hindered by limited useful regulatory genes. Here by repeatable phenotypic characterization of fixed recombinant individuals, we report a quantitative genetic locus, Seed Dormancy 6 (SD6), from aus-type rice, encoding a basic helix-loop-helix (bHLH) transcription factor, which underlies the natural variation of seed dormancy. SD6 and another bHLH factor inducer of C-repeat binding factors expression 2 (ICE2) function antagonistically in controlling seed dormancy by directly regulating the ABA catabolism gene ABA8OX3, and indirectly regulating the ABA biosynthesis gene NCED2 via OsbHLH048, in a temperature-dependent manner. The weak-dormancy allele of SD6 is common in cultivated rice but undergoes negative selection in wild rice. Notably, by genome editing SD6 and its wheat homologs, we demonstrated that SD6 is a useful breeding target for alleviating PHS in cereals under field conditions.
由于种子休眠缺失导致的收获前发芽（PHS）严重威胁着全球作物生产。作为一个复杂的数量性状，由于有用的调控基因有限，培育具有合适种子休眠性的作物品种受到阻碍。在此，通过对固定重组个体进行可重复的表型鉴定，我们报道了一个来自籼稻类型水稻的数量遗传位点——种子休眠6（SD6），它编码一个碱性螺旋-环-螺旋（bHLH）转录因子，是种子休眠自然变异的基础。SD6和另一个C-重复结合因子表达诱导子2（ICE2）这一bHLH因子，通过直接调控脱落酸（ABA）分解代谢基因ABA8OX3，并通过OsbHLH048间接调控ABA生物合成基因NCED2，以温度依赖的方式在控制种子休眠中发挥拮抗作用。SD6的弱休眠等位基因在栽培稻中很常见，但在野生稻中经历负选择。值得注意的是，通过对SD6及其小麦同源基因进行基因组编辑，我们证明SD6是在田间条件下减轻谷物收获前发芽的一个有用的育种靶点。
