State Key Laboratory of Crop Stress Biology for Arid Areas, College of Life Science, Northwest A&F University, Yangling, Shaanxi, 712100, China.
Hybrid Rapeseed Research Centre of Shaanxi Province, Yangling, Shaanxi, 712100, China.
Biochem Biophys Res Commun. 2018 Sep 5;503(2):495-500. doi: 10.1016/j.bbrc.2018.04.185. Epub 2018 Jun 30.
Abscisic acid (ABA) signaling is a vital physiological step that is used by many land plants to fight against environmental stress. As components of the linear ABA signaling pathway, clade A protein phosphatases type 2C (PP2C-As) are mainly inhibited by PYRABACTIN RESISTANCE1/PYR1-LIKE/REGULATORY COMPONENTS OF ABA RECEPTORS (PYLs)-type receptors upon their binding to ABA. Here, we show that the genome of Brassica rapa encodes 14 putative clade A PP2C-like proteins (BrPP2C-As). Two of these BrPP2C-As, Bra025964 and Bra016595, show high similarity to the HAB2 (Homology to ABI2) protein in Arabidopsis. RNAseq data reveal that nearly all BrPP2C-As, like BrHAB2a (Bra025964) and BrHAB2b (Bra016595), were highly expressed in at least one tissue. Overexpression of BrHAB2a conferred ABA insensitivity to Arabidopsis thaliana seedlings. Furthermore, the phosphatase activity of BrHAB2a could be inhibited by AtPYL1 or BrPYL1 in the presence of ABA. Overall, these results suggest that BrHAB2a is a functional PP2C-A like protein phosphotase and a key component of ABA signaling in Brassica rapa.
脱落酸（ABA）信号是许多陆地植物用来对抗环境胁迫的重要生理步骤。作为线性 ABA 信号通路的组成部分，clade A 蛋白磷酸酶 2C（PP2C-As）主要被 PYRABACTIN RESISTANCE1/PYR1-LIKE/ABA RECEPTORS（PYLs）-type 受体结合 ABA 所抑制。在这里，我们展示了芸薹属白菜基因组编码 14 种假定的 clade A PP2C 样蛋白（BrPP2C-As）。其中两种 BrPP2C-As，Bra025964 和 Bra016595，与拟南芥中的 HAB2（ABI2 同源物）蛋白具有高度相似性。RNAseq 数据显示，几乎所有的 BrPP2C-As，如 BrHAB2a（Bra025964）和 BrHAB2b（Bra016595），在至少一种组织中都有高表达。BrHAB2a 的过表达使拟南芥幼苗对 ABA 不敏感。此外，在 ABA 存在的情况下，AtPYL1 或 BrPYL1 可以抑制 BrHAB2a 的磷酸酶活性。总的来说，这些结果表明 BrHAB2a 是一种功能性的 PP2C-A 样蛋白磷酸酶，是芸薹属白菜 ABA 信号转导的关键组成部分。
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