Misregulation of phosphoinositides in Arabidopsis thaliana decreases pollen hydration and maternal fertility
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Phosphoinositides are important lipids involved in membrane identity, vesicle trafficking, and intracellular signaling. In recent years, phosphoinositides have been shown to play a critical role in polarized secretion in plants, as perturbations of phosphoinositide metabolism, through loss of function mutants, result in defects in root hair elongation and pollen tube growth, where polarized secretion occurs rapidly. In the Brassicaceae, responses of stigmatic papillae to compatible pollen are also thought to involve highly regulated secretory events to facilitate pollen hydration and penetration of the pollen tube through the stigmatic surface. We therefore sought to analyze the female sporophyte fertility of the root hair defective4-1 mutant and the PI 4-kinase β1/β2 double mutant, which differentially affect phosphatidylinositol-4-phosphate (PI4P) levels. Stigmas from both mutants supported slower rates of pollen grain hydration, and the fecundity of these mutants was also diminished as a result of failed pollination events. This study therefore concludes that PI4P is integral to appropriate pistil responses to compatible pollen.
KeywordsPollen-pistil interactions Compatible pollen PI 4-kinase Phosphoinositide phosphatase Arabidopsis
We are very grateful to Dr. Erik Nielsen for helpful discussions and for providing the rhd4-1 and pi4kβ1/β2 mutants used in this study. We also thank Emily Indriolo for critical reading of the manuscript. LAC was supported by an Ontario Graduate Scholarship and a graduate scholarship from the Natural Sciences and Engineering Research Council of Canada (NSERC). Research in the laboratory of DRG is supported by grants from NSERC and a Canada Research Chair to DRG.
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