背景回顾：Plants have evolved signaling mechanisms that guide growth away from adverse environments that can cause yield losses. Root halotropism is a sodium-specific negative tropism that is crucial for surviving and thriving under high salinity. 

提出问题：Although root halotropism was discovered some years ago, the underlying molecular and cellular mechanisms remain unknown. 

主要发现：Here, we show that abscisic acid (ABA)-mediated root twisting determines halotropism in Arabidopsis. 

结果1-ABA-SnRK2.6-SP2L：An ABA-activated SnRK2 protein kinase (SnRK2.6) phosphorylates the microtubule-associated protein SP2L at Ser406, which induces a change in the anisotropic cell expansion at the root transition zone and is required for root twisting during halotropism. 

结果2-微管重定向：Salt stress triggers SP2L-mediated cortical microtubule reorientation, which guides cellulose microfibril patterns. 

结论：Our findings thus outline the molecular mechanism of root halotropism and indicate that anisotropic cell expansion through microtubule reorientation and microfibril deposition has a central role in mediating tropic responses.

Figure 7. Schematic model for ABA- and SP2L-mediated root halotropism.

植物演化出信号转导机制来避免可能会导致产量损失的不利环境。根的避盐性是一种钠离子特异性的负向性，对于植物在高盐环境下的存活和茁壮生长至关重要。尽管几年前就已经发现的根的避盐性，但是潜在的分子和细胞学机制仍不清楚。本文中，作者发现ABA介导的根扭曲决定了拟南芥的根避盐性。一个受到ABA激活的SnRK2蛋白激酶SnRK2.6能够磷酸化微管相关蛋白SP2L上406号位的丝氨酸残基，从而诱导根过渡区（位于根尖分生区和伸长区之间）的各向异性细胞扩张的改变，这对于拟南芥根避盐性过程中的根扭曲是必要的。盐胁迫会诱导SP2L介导的皮层微管的重定向，指导纤维素微纤丝模式。本文的研究结果揭示了一个植物根避盐性的分子机制，通过微管重定向和微纤丝沉积作用的各向异性细胞扩张在根的向性响应方面发挥重要作用。

** 赵 杨 **