title: The calcineurin B-like Ca2+ sensors CBL1 and CBL9 function in pollen germination and pollen tube growth in Arabidopsis.
abstract: 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.
authors.affiliation: Institut für Biologie und Biotechnologie der Pflanzen, Universität Münster, Schlossplatz 4, 48149 Münster, Germany.
authors.forename: Anette
authors.initials: A
authors.lastname: Mähs
authors.forename: Leonie
authors.initials: L
authors.lastname: Steinhorst
authors.forename: Jian-Pu
authors.initials: JP
authors.lastname: Han
authors.forename: Li-Ke
authors.initials: LK
authors.lastname: Shen
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.forename: Jörg
authors.initials: J
authors.lastname: Kudla
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000254:growth & development / Q000378:metabolism* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D018525:Germination / Q000187:drug effects; D006706:Homeostasis / Q000187:drug effects; D009154:Mutation; D053205:Pollen Tube / Q000033:anatomy & histology / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D021381:Protein Transport; D014026:Nicotiana / Q000235:genetics / Q000254:growth & development
chemical_list: D029681:Arabidopsis Proteins; C514582:CBL9 protein, Arabidopsis; D002135:Calcium-Binding Proteins; C483419:calcineurin B-like protein 1, Arabidopsis; D011188:Potassium; D002118:Calcium
keywords: CBL; calcium; pollen tube growth; potassium.