Gu Dachuan, Wang Yahan, Zhao Minglei, Chen Hangcong, Wu Suhua, Jin Xia, Deng Ling, Ji Rujun, Xu Jinyan, Zheng Feng, Liu Xuncheng
Guangdong Provincial Key Laboratory of Applied Botany, Key Laboratory of South China Agricultural Plant Molecular Analysis and Genetic Improvement, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, 510650, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China.
College of Horticulture, South China Agricultural University, Guangzhou, China.
Plant Commun. 2025 Sep 4:101517. doi: 10.1016/j.xplc.2025.101517.
Seed germination is a critical step in the life cycle of plants. The far-red/red light photoreceptor phytochrome B (phyB) plays a dominant role in promoting seed germination, mainly by modulating the metabolism of gibberellin (GA) and abscisic acid (ABA), although the underlying mechanism remains poorly understood. In this study, we identified BREVIPEDICELLUS (BP)/KNAT1, a KNOX transcription factor that acted downstream of phyB and activated light-initiated seed germination in Arabidopsis thaliana. BP underwent ubiquitination modification and was degraded through the 26S proteasome pathway. PhyB directly interacted with BP in vitro and in vivo and stabilized BP protein by decreasing its ubiquitination in imbibed seeds. A genome-wide transcriptomic analysis revealed that BP and phyB co-regulated the expression of genes related to ABA biosynthesis and signaling transduction, seed dormancy, and cell wall organization. BP repressed the expression of two key ABA biosynthetic genes, NCED6 and NCED9, and decreased ABA levels in imbibed seeds under phyB-activated conditions. BP directly bound to NCED6 and NCED9 and repressed their expression by increasing the levels of H3K27me3, a repressive histone modification marker. Genetic analysis revealed that NCED6/NCED9 acted epistasis of BP in phyB-dependent seed germination. Taken together, this study reveals a transcriptional module consisting of phyB-BP-NCED6/9, which transfers light signals that inhibit ABA biosynthesis, thereby promoting light-induced seed germination.
种子萌发是植物生命周期中的关键步骤。远红光/红光光感受器phytochrome B（phyB）在促进种子萌发中起主导作用，主要通过调节赤霉素（GA）和脱落酸（ABA）的代谢，尽管其潜在机制仍知之甚少。在本研究中，我们鉴定了BREVIPEDICELLUS（BP）/KNAT1，一种KNOX转录因子，它在phyB下游起作用并激活拟南芥中光启动的种子萌发。BP经历泛素化修饰并通过26S蛋白酶体途径降解。phyB在体外和体内直接与BP相互作用，并通过降低其在吸胀种子中的泛素化来稳定BP蛋白。全基因组转录组分析表明，BP和phyB共同调节与ABA生物合成、信号转导、种子休眠和细胞壁组织相关的基因表达。BP抑制两个关键ABA生物合成基因NCED6和NCED9的表达，并在phyB激活条件下降低吸胀种子中的ABA水平。BP直接结合NCED6和NCED9，并通过增加抑制性组蛋白修饰标记H3K27me3的水平来抑制它们的表达。遗传分析表明，NCED6/NCED9在phyB依赖的种子萌发中起BP的上位作用。综上所述，本研究揭示了一个由phyB-BP-NCED6/9组成的转录模块，该模块传递抑制ABA生物合成的光信号，从而促进光诱导的种子萌发。
