Institut für Biologie und Biotechnologie der Pflanzen, Universität Münster, Schlossplatz 4, 48149 Münster, Germany.
Mol Plant. 2013 Jul;6(4):1149-62. doi: 10.1093/mp/sst095. Epub 2013 Jun 5.
Ca(2+) has been established as an important second messenger regulating pollen germination and tube growth. However, to date, only a few signaling components have been identified to decode and relay Ca(2+) signals in growing pollen tubes. Here, we report a function for the calcineurin B-like (CBL) Ca(2+) sensor proteins CBL1 and CBL9 from Arabidopsis in pollen germination and tube growth. Both proteins are expressed in mature pollen and pollen tubes and impair pollen tube growth and morphology if transiently overexpressed in tobacco pollen. The induction of these phenotypes requires efficient plasma membrane targeting of CBL1 and is independent of Ca(2+) binding to the fourth EF-hand of CBL1. Overexpression of CBL1 or its closest homolog CBL9 in Arabidopsis renders pollen germination and tube growth hypersensitive towards high external K(+) concentrations while disruption of CBL1 and CBL9 reduces pollen tube growth under low K(+) conditions. Together, our data identify a crucial function for CBL1 and CBL9 in pollen germination and tube growth and suggest a model in which both proteins act at the plasma membrane through regulation of K(+) homeostasis.
钙离子（Ca(2+)）已被确立为调节花粉萌发和管生长的重要第二信使。然而，迄今为止，只有少数信号成分被鉴定出来，以解码和传递生长花粉管中的 Ca(2+)信号。在这里，我们报告了拟南芥中的钙调磷酸酶 B 样（CBL）Ca(2+)传感器蛋白 CBL1 和 CBL9 在花粉萌发和管生长中的功能。这两种蛋白都在成熟花粉和花粉管中表达，如果在烟草花粉中瞬时过表达，会损害花粉管的生长和形态。这些表型的诱导需要 CBL1 有效的质膜靶向，并且不依赖于 CBL1 的第四 EF 手对 Ca(2+)的结合。CBL1 或其最接近的同源物 CBL9 在拟南芥中的过表达使花粉萌发和管生长对高外部 K(+)浓度敏感，而 CBL1 和 CBL9 的缺失则降低了低钾（K(+)）条件下花粉管的生长。总之，我们的数据确定了 CBL1 和 CBL9 在花粉萌发和管生长中的关键功能，并提出了一个模型，其中这两种蛋白通过调节 K(+)稳态在质膜上发挥作用。
