Regulatory feedback mechanisms in rice crown root development

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Geng et al. reveal a feedback system that orchestrates the expression of genes controlling crown root development in rice (Oryza sativa) and uncover a molecular rheostat of this system.

https://doi.org/10.1093/plcell/koad318

By Leping Geng and Yu Zhao

National Key Laboratory of Crop Genetic Improvement, Hubei Hongshan Laboratory, Huazhong Agricultural University, Wuhan, 430070, China

Background: Crown roots (also called adventitious roots) are the main components of root systems in cereals and play essential roles in nutrient uptake, stress tolerance, and yield. WUSCHEL-related homeobox (WOX) and lateral organ boundaries domain (LBD) transcription factors regulate adventitious root morphogenesis in angiosperms. However, the molecular mechanisms by which these transcription factors regulate rice crown root development remain unclear.

Questions: Does LBD16 control crown root development in rice (Oryza sativa)? What is the relationship between LBD16 and WOX11 in governing rice crown root morphogenesis?

Findings: LBD16 promotes the emergence and outgrowth of crown roots in rice by influencing cell division. WOX11 recruits the histone demethylase JMJ706 that removes histone H3 lysine 9 dimethylation (H3K9me2) from the LBD16 promoter, thereby activating LBD16 transcription. More importantly, LBD16 competes with JMJ706 for interaction with WOX11 and represses its own upregulation by the WOX11–JMJ706 complex. These results reveal a feedback regulatory system controlling the expression of genes orchestrating crown root development in rice, in which LBD16 acts as a molecular rheostat.

Next steps: Root system improvement will enhance rice environmental adaptation and yield potential. Future research will focus on the underlying mechanisms mediating WOX11 recruitment of JMJ706 and removal of H3K9me2 leading to altered root architecture. Such advances would help breeders cultivate excellent varieties with ideal root systems.

Reference:

Leping Geng, Mingfang Tan, Qiyu Deng, Yijie Wang, Ting Zhang, Xiaosong Hu, Miaomiao Ye, Xingming Lian, Dao-Xiu Zhou, Yu Zhao. (2024). Transcription factors WOX11 and LBD16 function with histone demethylase JMJ706 to control crown root development in rice https://doi.org/10.1093/plcell/koad318

 背景：冠根（即不定根）是禾本科作物如水稻、小麦等根系最主要的组成成分，在营养吸收、土壤环境适应以及产量提升等方面起着重要的作用。人们发现两类重要的转录因子WOX和LBD 在被子植物不定根形态建成中发挥着关键的作用。然而，这两类转录因子调控水稻冠根发育的分子机制并不清楚。

问题：LBD调控水稻冠根发育的分子机制是什么？在调控水稻冠根发育中LBD和WOX家族蛋白的相互关系是什么？

发现：我们发现LBD16通过促进冠根原基分生组织细胞分裂而使原基伸长生长，其作用机制是WOX11招募组蛋白JMJ706去甲基化酶特异地去除LBD16启动子上的H3K9me2，从而激活LBD16的转录。更为重要的是，当细胞中LBD16蛋白增加后，就可以与JMJ706竞争性地与WOX11互作，抑制LBD16 mRNA的转录，从而维持细胞中LBD16水平的稳定。因此，我们的研究结果揭示了WOX-LBD控制水稻冠根发育的负反馈调节系统。

下一步工作计划：根系的改良有助于提高作物的环境适应性和产量。我们未来的研究将集中在该反馈系统和表观修饰因子如何相互作用促进水稻根系构型改变，为育种家培育出具有理想根系构型的水稻品种做出贡献。