Department of Plant and Microbial Biology, University of California at Berkeley, Berkeley, CA, USA.
College of Life Sciences, Capital Normal University, Beijing, China.
Cell Res. 2023 Jan;33(1):71-79. doi: 10.1038/s41422-022-00754-3. Epub 2023 Jan 2.
Pollen tube tip growth requires intricate Ca signaling. Recent studies have also identified rapid alkalization factor (RALF)-family peptides and their receptors as critical components for pollen tube tip growth and integrity. The functional relationship of RALF and calcium signaling modules remains largely unclear. Here we report that disruption of RALF signaling pathway abolished the cytosolic Ca gradient in the pollen tube, indicating that Ca signaling is downstream of the RALF signaling pathway. We identified MILDEW RESISTANCE LOCUS O (MLO) family proteins MLO1, 5, 9, 15, as Ca channels required for Ca influx and pollen tube integrity. We further reconstituted the biochemical pathway in which signaling via RALF and RALF receptors activated MLO1/5/9/15 calcium channels. Together, we conclude that RALF peptides derived from pollen tube bind to their receptors to establish pollen tube Ca gradient through activation of the MLO channels. Our finding has thus provided a mechanistic link between the RALF signaling pathway and Ca signaling in controlling pollen tube integrity and growth.
花粉管顶端生长需要复杂的钙信号转导。最近的研究还发现，快速碱化因子（RALF）家族肽及其受体是花粉管顶端生长和完整性的关键组成部分。RALF 和钙信号转导模块之间的功能关系在很大程度上仍不清楚。在这里，我们报告称，RALF 信号通路的破坏消除了花粉管中的胞质 Ca 梯度，表明 Ca 信号转导是 RALF 信号通路的下游。我们鉴定了 MILDEW RESISTANCE LOCUS O（MLO）家族蛋白 MLO1、5、9、15 作为 Ca 通道，它们是 Ca 内流和花粉管完整性所必需的。我们进一步重建了生化途径，其中 RALF 信号和 RALF 受体通过激活 MLO1/5/9/15 钙通道来传递信号。总之，我们的结论是，花粉管中衍生的 RALF 肽与它们的受体结合，通过激活 MLO 通道来建立花粉管 Ca 梯度。我们的发现因此提供了 RALF 信号通路和 Ca 信号转导在控制花粉管完整性和生长中的机制联系。
