Phosphatidylinositol-4,5-bisphosphate influences Nt-Rac5-mediated cell expansion in pollen tubes of Nicotiana tabacum.
The regulation of pollen tube growth by the phospholipid phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P(2) ) is not well understood. The Arabidopsis genome encodes two type A phosphatidylinositol-4-phosphate (PI4P) 5-kinases, PIP5K10 and PIP5K11, which are exclusively expressed in pollen and produce PtdIns(4,5)P(2) in vitro. Fluorescence-tagged PIP5K10 and PIP5K11 localized to lateral subapical plasma membrane microdomains in tobacco pollen tubes in a pattern closely resembling the distribution of PtdIns(4,5)P(2,) with the exception of notably weaker association at the extreme apex. Overexpression of PIP5K10 or PIP5K11 in tobacco pollen tubes resulted in severe tip swelling and altered actin fine structure similar to that reported for overexpression of tobacco Nt-Rac5, a monomeric GTPase known to regulate the actin cytoskeleton. Increased sensitivity of Arabidopsis pip5k10 pip5k11 double mutant pollen tubes to Latrunculin B (LatB) further supports a role for type A PI4P 5-kinases in controlling the actin cytoskeleton. Despite the disruption of both its type A PI4P 5-kinases, the pip5k10 pip5k11 double mutant was fertile, indicating that one of the remaining type B PI4P 5-kinase isoforms might be functionally redundant with PIP5K10 and PIP5K11. Antagonistic effects of PIP5K11 and the Nt-Rac5-specific guanine nucleotide dissociation inhibitor, Nt-RhoGDI2, on tip swelling observed in coexpression-titration experiments indicate a link between PtdIns(4,5)P(2) and Rac-signaling in pollen tubes. The data suggest that type A PI4P 5-kinases influence the actin cytoskeleton in pollen tubes in part by counteracting Nt-RhoGDI2, possibly contributing to the control of the pool of plasma membrane-associated Nt-Rac5.
Department of Plant Biochemistry, Albrecht-von-Haller-Institute for Plant Sciences, Georg-August-University Göttingen, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany.
Till
T
Ischebeck
Irene
I
Stenzel
Franziska
F
Hempel
Xu
X
Jin
Alina
A
Mosblech
Ingo
I
Heilmann
D000199:Actins / Q000737:chemistry; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000235:genetics / Q000378:metabolism; D016254:Mutagenesis, Insertional; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D053205:Pollen Tube / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D053778:Thiazolidines / Q000494:pharmacology; D014026:Nicotiana / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
D000199:Actins; D029681:Arabidopsis Proteins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D004269:DNA, Bacterial; D020730:Guanine Nucleotide Dissociation Inhibitors; D019269:Phosphatidylinositol 4,5-Diphosphate; D010940:Plant Proteins; C036483:T-DNA; D053778:Thiazolidines; D017853:Phosphotransferases (Alcohol Group Acceptor); C020077:1-phosphatidylinositol-4-phosphate 5-kinase; D020744:rac GTP-Binding Proteins; C037068:latrunculin B