2018年1月16日PNAS在线发表了题目为“Regulation of the stability of RGF1 receptor by the ubiquitin-specific proteases UBP12/UBP13 is critical for root meristem maintenance”的文章。

该文章为河北师范大学生命科学学院博士生安志超、刘玉良为共第一作者，汤文强教授和孙玉教授为共同通讯作者。

根是植物的重要器官，不但和植物的水分和营养吸收相关，还是许多植物生长调节物质合成的重要场所。植物根的发育主要受CLE40途径、RGF1途径和SHR-SCR途径等三条遗传途径调节，但它们遗传通路作用分子机理都仍不清楚。汤文强教授课题组的最新研究结果发现拟南芥中两个高度同源的蛋白去泛素化蛋白酶UBP12和UBP13能通过调节小肽激素RGF1信号传导途径来调节拟南芥根的生长发育。ubp12,13双突变体根非常短小，根尖分生区细胞数目少，对RGF1不敏感。通过生物化学、遗传学和分子生物学的研究手段，汤文强课题组证明了UBP12/13能和RGF1的受体RGFR1（有时也被称为RGI1）直接相互作用，抑制RGF1结合RGFR1后诱导的RGFR1的泛素化降解。UBP12/13通过维持根尖分生区细胞质膜上RGFR1的数目来保持根尖分生区细胞对RGF1的敏感性，从而保证根尖分生区细胞处于旺盛的分裂、生长状态，维持根的生长发育。

本项研究的重要意义还在于发现蛋白的可逆泛素化也是调节质膜受体激酶作用的重要调控方式。这是汤文强课题组继2016年发现蛋白磷酸酶PP2A调节受体激酶BRI1的活性之后，对质膜上受体激酶活性调节机制的又一重要发现。

ROOT MERISTEM GROWTH FACTOR (RGF) 1 is an important peptide hormone that regulates root growth. Upon binding to its receptor, RGFR1, RGF1 regulates the expression of two transcription factors, PLETHORA 1 and 2 (PLT1/2), to influence root meristem development. Here, we show that the ubiquitin-specific proteases UBP12 and UBP13 are positive regulators of root meristem development and that UBP13 interacts directly with RGF1 receptor (RGFR1) and its close homolog RGFR2. The ubp12,13 double-mutant root is completely insensitive to exogenous applied RGF1. Consistent with this result, RGF1-induced ubiquitination and turnover of RGFR1 protein were accelerated in ubp12,13-mutant plants but were delayed in transgenic plants overexpressing UBP13. Genetic analysis showed that PLT2 or RGFR1 overexpression partially rescued the short-root phenotype and the reduced cortical root meristem cell number in ubp12,13 plants. Together, our results demonstrate that UBP12/13 are regulators of the RGF1–RGFR1–PLT1/2 signaling pathway and that UBP12/13 can counteract RGF1-induced RGFR1 ubiquitination, stabilize RGFR1, and maintain root cell sensitivity to RGF1.

Fig. 1. UBP12 and UBP13 regulate PLT1 and PLT2 expression.