Zhang Haiwen, Feng Hao, Zhang Junwen, Ge Rongchao, Zhang Liyuan, Wang Yunxiao, Li Legong, Wei Jianhua, Li Ruifen
Beijing Agro-biotechnology Research Center, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China.
Beijing Key Laboratory of Agricultural Genetic Resources and Biotechnology, Beijing, China.
J Exp Bot. 2020 Jul 6;71(14):4345-4358. doi: 10.1093/jxb/eraa191.
K+/Na+ homeostasis is the primary core response for plant to tolerate salinity. Halophytes have evolved novel regulatory mechanisms to maintain a suitable K+/Na+ ratio during long-term adaptation. The wild halophyte Hordeum brevisubulatum can adopt efficient strategies to achieve synergistic levels of K+ and Na+ under high salt stress. However, little is known about its molecular mechanism. Our previous study indicated that HbCIPK2 contributed to prevention of Na+ accumulation and K+ reduction. Here, we further identified the HbCIPK2-interacting proteins including upstream Ca2+ sensors, HbCBL1, HbCBL4, and HbCBL10, and downstream phosphorylated targets, the voltage-gated K+ channel HbVGKC1 and SOS1-like transporter HbSOS1L. HbCBL1 combined with HbCIPK2 could activate HbVGKC1 to absorb K+, while the HbCBL4/10-HbCIPK2 complex modulated HbSOS1L to exclude Na+. This discovery suggested that crosstalk between the sodium response and the potassium uptake signaling pathways indeed exists for HbCIPK2 as the signal hub, and paved the way for understanding the novel mechanism of K+/Na+ homeostasis which has evolved in the halophytic grass.
钾离子/钠离子稳态是植物耐受盐胁迫的主要核心反应。盐生植物在长期适应过程中进化出了新的调节机制，以维持合适的钾离子/钠离子比率。野生盐生植物野大麦能够采用有效的策略，在高盐胁迫下实现钾离子和钠离子的协同水平。然而，其分子机制尚不清楚。我们之前的研究表明，HbCIPK2有助于防止钠离子积累和钾离子减少。在此，我们进一步鉴定了与HbCIPK2相互作用的蛋白，包括上游钙离子传感器HbCBL1、HbCBL4和HbCBL10，以及下游磷酸化靶点，电压门控钾离子通道HbVGKC1和类SOS1转运蛋白HbSOS1L。HbCBL1与HbCIPK2结合可激活HbVGKC1以吸收钾离子，而HbCBL4/10-HbCIPK2复合物调节HbSOS1L以排出钠离子。这一发现表明，作为信号枢纽的HbCIPK2确实存在钠反应和钾吸收信号通路之间的串扰，为理解盐生草中进化出的钾离子/钠离子稳态新机制铺平了道路。
