title: A calcium-dependent protein kinase interacts with and activates a calcium channel to regulate pollen tube growth.
abstract: Calcium, as a ubiquitous second messenger, plays essential roles in tip-growing cells, such as animal neurons, plant pollen tubes, and root hairs. However, little is known concerning the regulatory mechanisms that code and decode Ca(2+) signals in plants. The evidence presented here indicates that a calcium-dependent protein kinase, CPK32, controls polar growth of pollen tubes. Overexpression of CPK32 disrupted the polar growth along with excessive Ca(2+) accumulation in the tip. A search of downstream effector molecules for CPK32 led to identification of a cyclic nucleotide-gated channel, CNGC18, as an interacting partner for CPK32. Co-expression of CPK32 and CNGC18 resulted in activation of CNGC18 in Xenopus oocytes where expression of CNGC18 alone did not exhibit significant calcium channel activity. Overexpression of CNGC18 produced a growth arrest phenotype coupled with accumulation of calcium in the tip, similar to that induced by CPK32 overexpression. Co-expression of CPK32 and CNGC18 had a synergistic effect leading to more severe depolarization of pollen tube growth. These results provide a potential feed-forward mechanism in which calcium-activated CPK32 activates CNGC18, further promoting calcium entry during the elevation phase of Ca(2+) oscillations in the polar growth of pollen tubes.
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA.
authors.forename: Liming
authors.initials: L
authors.lastname: Zhou
authors.forename: Wenzhi
authors.initials: W
authors.lastname: Lan
authors.forename: Yuanqing
authors.initials: Y
authors.lastname: Jiang
authors.forename: Wei
authors.initials: W
authors.lastname: Fang
authors.forename: Sheng
authors.initials: S
authors.lastname: Luan
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D011058:Pollen / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D053205:Pollen Tube / Q000201:enzymology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D011485:Protein Binding; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D014026:Nicotiana / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D014981:Xenopus
chemical_list: D029681:Arabidopsis Proteins; C000589714:CNGC18 protein, Arabidopsis; D054815:Cyclic Nucleotide-Gated Cation Channels; C000589713:CPK32 protein, Arabidopsis; D011494:Protein Kinases; D002118:Calcium
keywords: Ca2+ oscillations.; calcium-dependent protein kinase; cyclic nucleotide-gated channel; pollen tubes