Cystathionine beta-lyase is crucial for embryo patterning and the maintenance of root stem cell niche in Arabidopsis

First author: Guolan Liu; Affiliations: South China Agricultural University (华南农业大学): Guangzhou, China

Corresponding author: Li-Zhen Tao

The growth and development of roots in plants depends on the specification and maintenance of the root apical meristem. Here, we report the identification of CBL, a gene required for embryo and root development in Arabidopsis, and encodes cystathionine beta-lyase (CBL), which catalyzes the penultimate step in methionine (Met) biosynthesis, and which also led to the discovery of a previous unknown, but crucial, metabolic contribution by the Met biosynthesis pathway. CBL is expressed in embryos and shows quiescent center (QC)-enriched expression pattern in the root. cbl mutant has impaired embryo patterning, defective root stem cell niche, stunted root growth, and reduces accumulation of the root master regulators PLETHORA1 (PLT1) and PLT2. Furthermore, mutation in CBL severely decreases abundance of several PINFORMED (PIN) proteins and impairs auxin-responsive gene expression in the root tip. cbl seedlings also exhibit global reduction in histone H3 Lys-4 trimethylation (H3K4me3) and DNA methylation. Importantly, mutation in CBL reduces the abundance of H3K4me3 modification in PLT1/2 genes and downregulates their expression. Overexpression of PLT2 partially rescues cbl root meristem defect, suggesting that CBL acts in part through PLT1/2. Moreover, exogenous supplementation of Met also restores the impaired QC activity and the root growth defects of cbl. Taken together, our results highlight the unique role of CBL to maintain the root stem cell niche by cooperative actions between Met biosynthesis and epigenetic modification of key developmental regulators.

植物根的生长和发育依赖于根尖分生组织的特化和维持。本文中，作者报道了一个拟南芥中对于胚胎和根发育都必需的基因CBL，该基因编码一个胱硫醚-beta-裂合酶，能够催化甲硫氨酸生物合成的倒数第二个反应，这在之前的研究中是没有人发现的。CBL基因在胚胎中表达，并且在根的静止中心QC中富集表达。cbl突变体存在胚胎模式建成缺陷，根的干细胞龛也存在缺陷，根的生长发育不良，同时降低了根的主要调控因子PLT1和PLT2的积累。此外，CBL基因的突变还极大降低了一些PIN蛋白的丰度，导致根尖中的生长素响应基因表达受到影响。cbl的幼苗在H3K4me3和DNA甲基化方面均存在整体下降的情况。重要的是，CBL基因的突变导致了PLT1/2基因上H3K4me3修饰水平降低，并且下调了这两个基因的表达。过表达PLT2基因能够部分拯救cbl突变体根分生组织缺陷的表型，说明CBL基因的功能发挥部分通过PLT1/2。此外，补充外源的Met同样能够拯救cbl突变体QC活性和根生长的缺陷。综上，本文的研究揭示了CBL蛋白通过协调Met生物合成以及关键发育调控因子的表观修饰来作用于根干细胞龛的维持。

通讯：陶利珍 (http://life.scau.edu.cn/nav-staff-30002770.asp)

研究方向：以拟南芥和水稻等模式植物为实验材料，采用分子生物学、细胞生物学、生物化学和遗传学手段，研究植物激素信号及其激素信号间互作在调节植物生长、 发育和植物对环境适应的分子机理。

doi: 10.1111/tpj.14343

Journal: the plant journal

Accept date: April 01, 2019