Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan.
Plant Cell. 2014 Feb;26(2):636-49. doi: 10.1105/tpc.113.121350. Epub 2014 Feb 25.
In the Brassicaceae, intraspecific non-self pollen (compatible pollen) can germinate and grow into stigmatic papilla cells, while self-pollen or interspecific pollen is rejected at this stage. However, the mechanisms underlying this selective acceptance of compatible pollen remain unclear. Here, using a cell-impermeant calcium indicator, we showed that the compatible pollen coat contains signaling molecules that stimulate Ca(2+) export from the papilla cells. Transcriptome analyses of stigmas suggested that autoinhibited Ca(2+)-ATPase13 (ACA13) was induced after both compatible pollination and compatible pollen coat treatment. A complementation test using a yeast Saccharomyces cerevisiae strain lacking major Ca(2+) transport systems suggested that ACA13 indeed functions as an autoinhibited Ca(2+) transporter. ACA13 transcription increased in papilla cells and in transmitting tracts after pollination. ACA13 protein localized to the plasma membrane and to vesicles near the Golgi body and accumulated at the pollen tube penetration site after pollination. The stigma of a T-DNA insertion line of ACA13 exhibited reduced Ca(2+) export, as well as defects in compatible pollen germination and seed production. These findings suggest that stigmatic ACA13 functions in the export of Ca(2+) to the compatible pollen tube, which promotes successful fertilization.
在十字花科植物中，种内非自身花粉（亲和花粉）可以发芽并生长成柱头乳突细胞，而此时自身花粉或种间花粉则被排斥。然而，这种亲和花粉选择性接受的机制尚不清楚。在这里，我们使用一种非细胞渗透性的钙指示剂，表明亲和花粉外被含有信号分子，刺激乳突细胞中的 Ca(2+)输出。柱头的转录组分析表明，在亲和授粉和亲和花粉外被处理后，自动抑制 Ca(2+)-ATPase13（ACA13）被诱导。使用缺乏主要 Ca(2+)转运系统的酵母酿酒酵母菌株进行的互补测试表明，ACA13 确实作为一种自动抑制的 Ca(2+)转运体发挥作用。授粉后，ACA13 在乳突细胞和传递道中转录增加。ACA13 蛋白定位于质膜和靠近高尔基体的小泡中，并在授粉后花粉管穿透部位积累。ACA13 的 T-DNA 插入系的柱头表现出 Ca(2+)输出减少，以及亲和花粉萌发和种子产生缺陷。这些发现表明，柱头 ACA13 参与将 Ca(2+)输出到亲和花粉管中，从而促进受精成功。
