Qabi2-2表型：The hab1-1 abi1-2 abi2-2 pp2ca-1 quadruple mutant (Qabi2-2) seedlings lacking key negative regulators of ABA signaling, namely, clade A protein phosphatases type 2C (PP2Cs), show more apoplastic H+ efflux in roots and display an enhanced root growth under normal medium or water stress medium compared to the wild type. 

低浓度ABA处理模拟Qabi2-2表型：The presence of low ABA concentration (0.1 micromolar), inhibiting PP2C activity via monomeric ABA receptors, enhances root apoplastic H+ efflux and growth of the wild type, resembling the Qabi2-2 phenotype in normal medium.

Qabi2-2的向水性与不对称的H+外流：Qabi2-2 seedlings also demonstrate increased hydrotropism compared to the wild type in obliquely-oriented hydrotropic experimental system, and asymmetric H+ efflux in root elongation zone is crucial for root hydrotropism. 

ABI与下游AHA2：Moreover, we reveal that Arabidopsis ABA-insensitive 1, a key PP2C in ABA signaling, interacts directly with the C terminus of Arabidopsis plasma membrane H+-dependent adenosine triphosphatase 2 (AHA2) and dephosphorylates its penultimate threonine residue (Thr947), whose dephosphorylation negatively regulates AHA2.

 摘 要 

hab1-1abi1-2abi2-2pp2ca-1四突植株Qabi2-2缺少ABA信号转导的关键负调控因子PP2Cs。因此，相比于野生型，该突变体的幼苗在正常培养基或水分胁迫的培养基中，根组织表现出更多的质外体H+外流，并且根生长增强。用0.1mmol的低浓度ABA处理野生型植株，会通过单体ABA受体抑制PP2C的活性，增强正常培养基条件下的根组织质外体H+外流和根生长，模拟了Qabi2-2突变体的表型。另外，在倾斜的定向向水性试验中，相比于野生型，Qabi2-2幼苗还表现出向水性方面的增强，而根伸长区不对称的H+外流对于根的向水性是十分关键的。此外，作者还发现拟南芥ABA信号转导中一个关键的PP2C蛋白ABA-insensitive 1与拟南芥质膜H+依赖型三磷酸腺苷酶AHA2的C端发生直接互作，并去磷酸化该蛋白947号位上的苏氨酸残基，从而负调控AHA2。