Enzyme activities of A rabidopsis inositol polyphosphate kinases A t IPK 2α and A t IPK 2β are involved in pollen development, pollen tube guidance and embryogenesis

Inositol polyphosphate kinase ( IPK 2) is a key component of inositol polyphosphate signaling. There are two highly homologous inositol polyphosphate kinases ( A t IPK 2α and A t IPK 2β) in A rabidopsis. Previous studies that overexpressed or reduced the expression of A t IPK 2α and At IPK 2β revealed their roles in auxiliary shoot branching, abiotic stress responses and root growth. Here, we report that A t IPK 2 α and A t IPK 2 β act redundantly during pollen development, pollen tube guidance and embryogenesis. Single knock‐out mutants of atipk2 α and atipk2 β were indistinguishable from the wild type, whereas the atipk2 α atipk2 β double mutant could not be obtained. Detailed genetic and cytological investigations showed that the mutation of At IPK 2 α and At IPK 2 β resulted in severely reduced transmission of male gametophyte as a result of abnormal pollen development and defective pollen tube guidance. In addition, the early embryo development of the atipk2 α atipk2 β double mutant was also aborted. Expressing either catalytically inactive or substrate specificity‐altered variants of At IPK 2β could not rescue the male gametophyte and embryogenesis defects of the atipk2 α atipk2 β double mutant, implying that the kinase activity of A t IPK 2 is required for pollen development, pollen tube guidance and embryogenesis. Taken together, our results provide genetic evidence for the requirement of inositol polyphosphate signaling in plant sexual reproduction. Our results in this study demonstrate that AtIPK2α and AtIPK2β play an essential role in pollen development, pollen tube guidance and embryogenesis in a kinase activity‐dependent manner. Our data provides insights into the underlying molecular mechanism of pollen tube guidance.