NO調(diào)節(jié)花粉管生長(zhǎng)過程中胞內(nèi)外Ca2+的變化和細(xì)胞壁構(gòu)建

NO在極性生長(zhǎng)中的功能

NO調(diào)節(jié)花粉管生長(zhǎng)過程中胞內(nèi)外Ca2+的變化和細(xì)胞壁構(gòu)建

一氧化氮（NO） 在植物的生長(zhǎng)發(fā)育過程中具有非常重要的作用。近日，中科院植物所林金星研究組深入研究了裸子植物白皮松花粉管生長(zhǎng)過程中，NO對(duì)Ca2+、微絲骨架、囊泡轉(zhuǎn)運(yùn)和細(xì)胞壁構(gòu)建的調(diào)節(jié)作用。 NO作為重要的信號(hào)分子，參與調(diào)控花粉管極性生長(zhǎng)。通過應(yīng)用顯微注射、非損傷微測(cè)、免疫熒光標(biāo)記等技術(shù)發(fā)現(xiàn)NO釋放劑促進(jìn)花粉萌發(fā)和花粉管伸長(zhǎng)，并且具有濃度效應(yīng)，而抑制劑則抑制花粉萌發(fā)和花粉管生長(zhǎng)，同時(shí)使花粉管頂端膨大，喪失極性；NO釋放劑促進(jìn)胞外Ca2+內(nèi)流，頂端Ca2+濃度梯度增加，NO抑制劑抑制胞外Ca2+內(nèi)流，頂端Ca2+濃度梯度降低。 此外，NO釋放劑促進(jìn)囊泡運(yùn)輸，使花粉管頂端微絲束解聚，NO抑制劑具有相反的作用，同時(shí)NO使花粉管頂端酯化果膠增加而酸性果膠降低。 在白皮松花粉管中，NO促進(jìn)胞外Ca2+內(nèi)流，從而維持胞內(nèi)Ca2+濃度梯度，進(jìn)而影響花粉管頂端微絲骨架的組裝，促進(jìn)囊泡運(yùn)輸，使花粉管頂端酯化果膠累積，最終促進(jìn)花粉管的正常生長(zhǎng)。通過Ca2+流和細(xì)胞學(xué)實(shí)驗(yàn)結(jié)果，全面地認(rèn)識(shí)了NO在花粉管中極性生長(zhǎng)中的功能。 右圖:使用熒光標(biāo)記技術(shù)和非損傷微測(cè)技術(shù)得到的花粉管尖端Ca2+在NO釋放劑和抑制劑處理后的Ca2+含量以及Ca2+流的變化圖(右圖)。正值為外流，負(fù)值為內(nèi)流。

Summary
• Nitric oxide (NO) plays a key role in many physiological processes in plants, including pollen tube growth. Here, effects of NO on extracellular Ca²⁺ flux and microfilaments during cell wall construction in Pinus bungeana pollen tubes were investigated.
• Extracellular Ca²⁺ influx, the intracellular Ca²⁺ gradient, patterns of actin organization,vesicle trafficking and cell wall deposition upon treatment with the NO donor S-nitroso-N-acetylpenicillamine (SNAP), the NO synthase (NOS) inhibitor Nω-nitro-L-arginine(L-NNA) or the NO scavenger 2-(4-carboxyphenyl)-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) were analyzed.
• SNAP enhanced pollen tube growth in a dose-dependent manner, while L-NNA and cPTIO inhibited NO production and arrested pollen tube growth. Noninvasive detection and microinjection of a Ca²⁺ indicator revealed that SNAP promoted extracellular Ca²⁺ influx and increased the steepness of the tip-focused Ca²⁺ gradient, while cPTIO and L-NNA had the opposite effect. Fluorescence labeling indicated that SNAP, cPTIO and L-NNA altered actin organization, which subsequently affected vesicle trafficking. Finally, the configuration and/or distribution of cell wall components such as pectins and callose were significantly altered in response to L-NNA. Fourier transform infrared (FTIR) microspectroscopy confirmed the changes in the chemical composition of walls.
• Our results indicate that NO affects the configuration and distribution of cell wall components in pollen tubes by altering extracellular Ca2+ influx and F-actin organization.