TMK1-based auxin signaling regulates abscisic acid responses via phosphorylating ABI1/2 in <i>Arabidopsis</i>
Jie Yang, Hang He, Yuming He, Qiaozhen Zheng, Qingzhong Li, Xin Feng, Pengcheng Wang, Guochen Qin, Yangtao Gu, Ping Wu, Chao Peng, Shilei Sun, Yi Zhang, Mingzhang Wen, Rong Chen, Yang Zhao, Tongda Xu
Abstract
, which partially relies on TRANS-MEMBERANE KINASE 1 (TMK1), a key regulator in auxin signaling. We show that high auxin and TMK1 play essential and positive roles in ABA signaling through regulating ABA INSENSITIVE 1 and 2 (ABI1/2), two negative regulators of the ABA pathway. TMK1 inhibits the phosphatase activity of ABI2 by direct phosphorylation of threonine 321 (T321), a conserved phosphorylation site in ABI2 proteins, whose phosphorylation status is important for both auxin and ABA responses. This TMK1-dependent auxin signaling in the regulation of ABA responses provides a possible mechanism underlying the high auxin responses in plants and an alternative mechanism involved in the coordination between auxin and ABA signaling.