中科院最新PNAS文章

　　

　2月29日，《美国科学院院刊》（PNAS）杂志发表了中国科学院上海生命科学研究院植物生理生态研究所王永飞研究组题为Cyclic nucleotide-gated channel 18 is an essential Ca2+ channel in pollen tube tips for pollen tube guidance to ovules in Arabidopsis 的研究论文。该研究发现，CNGC18（cyclic nucleotide-gated channel 18）作为花粉管顶端质膜Ca2+通道，在拟南芥花粉管生长方向调控中发挥核心作用。

　　植物的花粉管生长方向受到来自胚珠的引导信号的精细调控，确保花粉管准确找到胚珠珠孔，并进入胚珠，从而使两个精子细胞被送入胚珠，完成双受精。其中，花粉管顶端质膜Ca2+通道被认为是控制花粉管生长方向的核心功能蛋白，通过介导和精细调控胞外Ca2+内流，调控花粉管顶端Ca2+浓度梯度，从而进一步调控花粉管的生长方向。因此，花粉管顶端质膜Ca2+通道就成为从胚珠引导信号到花粉管本身对胚珠引导信号的感知和应答系统这一完整信号链的关键环节。

    但该Ca2+通道的遗传身份几十年来一直是未知的，其通过介导和调控胞外Ca2+内流，从而调控花粉管生长方向的假说也一直缺乏遗传学证据的支持。该研究发现CNGC18是控制拟南芥花粉管生长方向最主要的一个质膜Ca2+通道，并用遗传学证据证实了其通过调控花粉管顶端Ca2+浓度梯度的动态变化，从而调控花粉管生长方向的假说。

    该研究很好地解决了这一植物生殖生物学领域的重要科学问题，为进一步解析整个花粉管生长方向的信号调控网络打开了一个突破口。

 

上海生科院揭示植物花粉管生长方向调控机理

原文摘要：

Cyclic nucleotide-gated channel 18 is an essential Ca2+ channel in pollen tube tips for pollen tube guidance to ovules in Arabidopsis

In flowering plants, pollen tubes are guided into ovules by multiple attractants from female gametophytes to release paired sperm cells for double fertilization. It has been well-established that Ca2+ gradients in the pollen tube tips are essential for pollen tube guidance and that plasma membrane Ca2+ channels in pollen tube tips are core components that regulate Ca2+ gradients by mediating and regulating external Ca2+ influx. Therefore, Ca2+ channels are the core components for pollen tube guidance. However, there is still no genetic evidence for the identification of the putative Ca2+ channels essential for pollen tube guidance. Here, we report that the point mutations R491Q or R578K in cyclic nucleotide-gated channel 18 (CNGC18) resulted in abnormal Ca2+ gradients and strong pollen tube guidance defects by impairing the activation of CNGC18 in Arabidopsis. The pollen tube guidance defects of cngc18-17 (R491Q) and of the transfer DNA (T-DNA) insertion mutant cngc18-1 (+/−) were completely rescued by CNGC18. Furthermore, domain-swapping experiments showed that CNGC18’s transmembrane domains are indispensable for pollen tube guidance. Additionally, we found that, among eight Ca2+ channels (including six CNGCs and two glutamate receptor-like channels), CNGC18 was the only one essential for pollen tube guidance. Thus, CNGC18 is the long-sought essential Ca2+ channel for pollen tube guidance in Arabidopsis.