自然通讯：NMT为质子泵激发花粉管生长并支撑其极性提供证据

旭月公司

2020/05/25 14:42

阅读：27

NMT作为生命科学底层核心技术，是建立活体创新科研平台的必备技术。2005年~2020年，NMT已扎根中国15年。2020年，中国NMT销往瑞士苏黎世大学，正式打开欧洲市场。

期刊：Nature Communications

主题：NMT为质子泵激发花粉管生长并支撑细胞极性提供直接证据

标题：Plasma membrane H+-ATPases sustain pollen tube

growth and fertilization

影响因子：11.878

检测指标：H+流速

检测样品：拟南芥

H+流实验处理方法：

拟南芥野生型和不同突变体（AHA6/8、AHA6/8/9、AHA6/9、AHA8/9）花粉管萌发3小时

H+流实验测试液成份：

0.1mM KCl，0.1mM CaCl2、0.1mM MgCl2、0.5mM NaCl，0.3mM MES，0.2mM Na2SO4，pH 6.0

作者：丹麦哥本哈根大学 Michael Palmgren、美国马里兰大学 jose A. Fejio

中文摘要（谷歌机翻）

花粉管是高度极化的顶端生长细胞，其依赖于细胞质的pH梯度进行信号传递和生长。已经提出了自抑制质膜质子（H⁺）ATPase（AHA）来激发花粉管生长并支撑细胞极性，但是，缺乏机械证据。

在这里，我们报道拟南芥中AHA6，AHA8和AHA9的综合损失会延迟花粉萌发并导致花粉管生长缺陷，从而导致生育力大大降低。aha突变体的花粉管具有降低的细胞外质子（H⁺）和阴离子通量，降低的胞质pH，降低的顶端-柄质子梯度和肌动蛋白组织缺陷。

此外，突变的花粉管具有较少的负膜电位，证实了AHA通过质膜超极化作用在花粉管生长中的机制作用。

我们的发现将AHAs定义为能维持定义细胞质pH的时空分布的离子回路的能量转换器，从而控制下游对花粉管伸长至关重要的pH依赖性机制，进而控制植物的育性。

Fig. 3 Reduced pollen tube growth in aha6 double and triple mutants is associated with reduced extracellular ion fluxes and intracellular pH gradients. (a) Representative WT pollen tube summarizing H⁺fluxes measured at the surface (arrows) and cytosolic pH gradient (false color). Arrow size is scaled with the flux intensity shown on the bottom bar, while direction denotes influx or efflux.(b) Extracellular H⁺ fluxes at the pollen tube tip. Violin plots show the probability density with color-filled curves obtained from individual observations (open gray circles), with boxplots (thick black lines and outliers asblack dots) overlaid with the mean and standard error (red circle and lines). (c) Extracellular H+ fluxes throughout the pollen tube sampled every 5 μm, averaged and interpolated with a local polynomial fit (loess) with n > 10 for all genotypes. Negative values indicate influx and positive values efflux. (d) Extracellular anion efflux at the tip.

Fig. 6 Model implicating plasma membrane H⁺-ATPases (AHAs) in the spatio-temporal control of ion fluxes and intracellular gradients required for actin organization during pollen tube growth. In the absence of AHAs (barrel shapes), extracellular H⁺ fluxes (colored arrows) and anionic efflux (black arrow) vanish, leading to a lower pH throughout the tube with ashallower cytosolic pH gradient (color fill heatmap), lower frequency of synchronized growth rate/[H+]cyt oscillations (magenta trace), and absence of organized actin at the tip (thin black lines), ultimately resulting in growth defects (represented by a shorter tube). Modified image of an Arabidopsis pollen grain by courtesy of Prof. David Twell, Electron Microscopy Facility, College of Life Sciences, University of Leicester.

英文摘要

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-toshank 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.