Department for Plant and Environmental Sciences, University of Copenhagen, 1871, Frederiksberg C, Denmark.
Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, 20742, USA.
Nat Commun. 2020 May 14;11(1):2395. doi: 10.1038/s41467-020-16253-1.
Pollen tubes are highly polarized tip-growing cells that depend on cytosolic pH gradients for signaling and growth. Autoinhibited plasma membrane proton (H) ATPases (AHAs) have been proposed to energize pollen tube growth and underlie cell polarity, however, mechanistic evidence for this is lacking. Here we report that the combined loss of AHA6, AHA8, and AHA9 in Arabidopsis thaliana delays pollen germination and causes pollen tube growth defects, leading to drastically reduced fertility. Pollen tubes of aha mutants had reduced extracellular proton (H) and anion fluxes, reduced cytosolic pH, reduced tip-to-shank proton gradients, and defects in actin organization. Furthermore, mutant pollen tubes had less negative membrane potentials, substantiating a mechanistic role for AHAs in pollen tube growth through plasma membrane hyperpolarization. Our findings define AHAs as energy transducers that sustain the ionic circuit defining the spatial and temporal profiles of cytosolic pH, thereby controlling downstream pH-dependent mechanisms essential for pollen tube elongation, and thus plant fertility.
花粉管是高度极化的顶端生长细胞，依赖细胞质 pH 梯度进行信号转导和生长。自动抑制的质膜质子（H）ATP 酶（AHAs）被认为能够为花粉管生长提供能量，并为细胞极性提供基础，然而，缺乏这方面的机制证据。在这里，我们报告拟南芥中 AHA6、AHA8 和 AHA9 的联合缺失会延迟花粉萌发并导致花粉管生长缺陷，从而导致生育力大幅降低。AHA 突变体的花粉管的胞外质子（H）和阴离子通量降低，细胞质 pH 值降低，尖端到柄部的质子梯度降低，肌动蛋白组织缺陷。此外，突变花粉管的膜电位更负，这证实了 AHAs 通过质膜超极化在花粉管生长中发挥机械作用。我们的研究结果将 AHAs 定义为能量转换器，它们维持着定义细胞质 pH 时空分布的离子回路，从而控制下游依赖 pH 的机制对于花粉管伸长至关重要，因此对于植物的生育能力至关重要。
