RLB (RICE LATERAL BRANCH) recruits PRC2-mediated H3K27 tri-methylation on OsCKX4 to regulate lateral branching
RLB (RICE LATERAL BRANCH) recruits PRC2-mediated H3K27 tri-methylation on OsCKX4 to regulate lateral branching
复制标题
RLB（水稻侧枝）在 OsCKX4 上招募 PRC2 介导的 H3K27 三甲基化来调节侧枝。
DOI：
10.1093/plphys/kiab494
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发表时间：
2021-11-03
期刊：
影响因子：
7.4
通讯作者：
Zhang, Jian
中科院分区：
文献类型：
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作者：
Wang, Huimei;Tong, Xiaohong;Zhang, Jian
侧枝结构是水稻生长发育的决定因素和目标性状。产量提高。细胞分裂素促进水稻分枝，然而，在水稻分枝细胞分裂素稳态微调的机制仍然在很大程度上未知。在这里，我们报告的RLB（水稻侧枝）的图位克隆编码核定位，KNOX型同源框蛋白从水稻细胞分裂素缺陷突变体显示更多的分蘖，稀疏的圆锥花序，有缺陷的小花形态，以及衰减芽再生愈伤组织。RLB直接与启动子结合，抑制水稻穗分支分生组织中高丰度的细胞分裂素氧化酶基因OsCKX 4的转录。OsCKX4过表达株表型为rlb，表现出OsCKX4水平上调。同时，RLB与Polycomb阻遏复合物2（PRC2）组分OsEMF 2b物理结合，并与H3K27me3共定位在OsCKX4启动子中，H3K27me3是PRC2介导的抑制性组蛋白修饰。我们认为RLB将PRC2募集到OsCKX4启动子上，表观遗传地抑制其转录，从而抑制细胞分裂素的释放，从而促进水稻的侧向分枝。此外，OsCKX4启动子下的反义抑制成功地增加了穗大小和单株小穗数，而不影响其他主要农艺性状。目前的研究提供了深入了解细胞分裂素稳态，植物的横向分支，也有希望的目标基因水稻遗传改良。
Lateral branches such as shoot and panicle are determining factors and target traits for rice (Oryza sativa L.) yield improvement. Cytokinin promotes rice lateral branching; however, the mechanism underlying the fine-tuning of cytokinin homeostasis in rice branching remains largely unknown. Here, we report the map-based cloning of RLB (RICE LATERAL BRANCH) encoding a nuclear-localized, KNOX-type homeobox protein from a rice cytokinin-deficient mutant showing more tillers, sparser panicles, defected floret morphology as well as attenuated shoot regeneration from callus. RLB directly binds to the promoter and represses the transcription of OsCKX4, a cytokinin oxidase gene with high abundance in panicle branch meristem. OsCKX4 over-expression lines phenocopied rlb which showed up-regulated OsCKX4 levels. Meanwhile, RLB physically binds to Polycomb repressive complex 2 (PRC2) component OsEMF2b and co-localized with H3K27me3, a suppressing histone modification mediated by PRC2, in the OsCKX4 promoter. We proposed that RLB recruits PRC2 to the OsCKX4 promoter to epigenetically repress its transcription, which suppresses the catabolism of cytokinin, thereby promoting rice lateral branching. Moreover, antisense inhibition of OsCKX4 under the LOG promoter successfully increased panicle size and spikelet number per plant without affecting other major agronomic traits. The current study provides insight into cytokinin homeostasis, lateral branching in plants, and also promising target genes for rice genetic improvement.