Abstract
Phosphatidylinositol-4-phosphate-5-kinase genes (PIP5Ks) play important roles in root hair formation. We investigated functions of PIP5K2, PIP5K3, and PIP5K4 genes in the regulation of root hair elongation during phosphate starvation. pip5k2 and pip5k4 mutants showed short root hair phenotypes similar to that of pip5k3. In pip5k2pip5k3 and pip5k3pip5k4 double mutants, those phenotypes were additively enhanced. These results indicate a redundant function in root hair elongation between these genes. pip5k3 and pip5k4, but not pip5k2, affected the enhancement of root hair elongation by phosphate starvation, indicating that PIP5K3 and PIP5K4 are involved in the phosphate starvation response. This is supported by the fact that promoters of PIP5K3 and PIP5K4 have recognition sites of the transcription factor, PHR1, which mediates phosphate-starvation responses. We constructed partial complementation plants by introducing PIP5K3 and PIP5K4 transgenes lacking PHR1-recognition sites into pip5k3 and pip5k4, respectively. These partial complementation plants are being used to investigate the biological significance of root hair elongation during phosphate starvation.
