Department of Plant and Environmental Sciences, University of Copenhagen, DK-1871, Frederiksberg, Denmark.
Physiol Plant. 2019 Jul;166(3):848-861. doi: 10.1111/ppl.12842. Epub 2018 Nov 20.
Plasma membrane H -ATPase pumps build up the electrochemical H gradients that energize most other transport processes into and out of plant cells through channel proteins and secondary active carriers. In Arabidopsis thaliana, the AUTOINHIBITED PLASMA MEMBRANE H -ATPases AHA1, AHA2 and AHA7 are predominant in root epidermal cells. In contrast to other H -ATPases, we find that AHA7 is autoinhibited by a sequence present in the extracellular loop between transmembrane segments 7 and 8. Autoinhibition of pump activity was regulated by extracellular pH, suggesting negative feedback regulation of AHA7 during establishment of an H gradient. Due to genetic redundancy, it has proven difficult to test the role of AHA2 and AHA7, and mutant phenotypes have previously only been observed under nutrient stress conditions. Here, we investigated root and root hair growth under normal conditions in single and double mutants of AHA2 and AHA7. We find that AHA2 drives root cell expansion during growth but that, unexpectedly, restriction of root hair elongation is dependent on AHA2 and AHA7, with each having different roles in this process.
质膜 H+-ATP 酶通过通道蛋白和次级主动载体将电化学 H+梯度建立起来，为大多数其他物质进出植物细胞的运输过程提供能量。在拟南芥中，AUTOINHIBITED PLASMA MEMBRANE H+-ATPases AHA1、AHA2 和 AHA7 在根表皮细胞中占主导地位。与其他 H+-ATPases 不同，我们发现 AHA7 被存在于跨膜段 7 和 8 之间的细胞外环中的序列自动抑制。泵活性的自动抑制受细胞外 pH 调节，这表明在 H+梯度建立过程中 AHA7 的负反馈调节。由于遗传冗余，证明很难测试 AHA2 和 AHA7 的作用，并且以前只在营养胁迫条件下观察到突变表型。在这里，我们在 AHA2 和 AHA7 的单突变体和双突变体中研究了正常条件下的根和根毛生长。我们发现 AHA2 在生长过程中驱动根细胞的扩张，但出乎意料的是，根毛伸长的限制依赖于 AHA2 和 AHA7，它们在这个过程中具有不同的作用。
