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自然 通訊：NMT為質(zhì)子泵激發(fā)花粉管生長并支撐其極性提供證據(jù)
NMT作為生命科學(xué)底層核心技術(shù)，是建立活體創(chuàng)新科研平臺(tái)的*技術(shù)。2005年~2020年，NMT已扎根中國15年。2020年，中國NMT銷往瑞士蘇黎世大學(xué)，正式打開歐洲市場(chǎng)。
期刊：Nature Communications
主題：NMT為質(zhì)子泵激發(fā)花粉管生長并支撐細(xì)胞極性提供直接證據(jù)
標(biāo)題：Plasma membrane H+-ATPases sustain pollen tube
growth and fertilization
影響因子：11.878
檢測(cè)指標(biāo)：H+流速
檢測(cè)樣品：擬南芥
H+流實(shí)驗(yàn)處理方法：
擬南芥野生型和不同突變體（AHA6/8、AHA6/8/9、AHA6/9、AHA8/9）花粉管萌發(fā)3小時(shí)
H+流實(shí)驗(yàn)測(cè)試液成份：
0.1mM KCl，0.1mM CaCl2、0.1mM MgCl2、0.5mM NaCl，0.3mM MES，0.2mM Na2SO4，pH 6.0
作者：丹麥哥本哈根大學(xué) Michael Palmgren、美國馬里蘭大學(xué) jose A. Fejio
中文摘要（谷歌機(jī)翻）
花粉管是高度極化的頂端生長細(xì)胞，其依賴于細(xì)胞質(zhì)的pH梯度進(jìn)行信號(hào)傳遞和生長。已經(jīng)提出了自抑制質(zhì)膜質(zhì)子（H+）ATPase（AHA）來激發(fā)花粉管生長并支撐細(xì)胞極性，但是，缺乏機(jī)械證據(jù)。
在這里，我們報(bào)道擬南芥中AHA6，AHA8和AHA9的綜合損失會(huì)延遲花粉萌發(fā)并導(dǎo)致花粉管生長缺陷，從而導(dǎo)致生育力大大降低。aha突變體的花粉管具有降低的細(xì)胞外質(zhì)子（H+）和陰離子通量，降低的胞質(zhì)pH，降低的-柄質(zhì)子梯度和肌動(dòng)蛋白組織缺陷。
此外，突變的花粉管具有較少的負(fù)膜電位，證實(shí)了AHA通過質(zhì)膜超極化作用在花粉管生長中的機(jī)制作用。
我們的發(fā)現(xiàn)將AHAs定義為能維持定義細(xì)胞質(zhì)pH的時(shí)空分布的離子回路的能量轉(zhuǎn)換器，從而控制下游對(duì)花粉管伸長至關(guān)重要的pH依賴性機(jī)制，進(jìn)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.