Arabidopsis VAC14 Is Critical for Pollen Development through Mediating Vacuolar Organization

Abstract

Pollen viability depends on dynamic vacuolar changes during pollen development involving increases and decreases of vacuolar volume through water and osmolite accumulation and vacuolar fission. Mutations in to, the genes encoding phosphatidylinositol 3,5-bisphosphate [PI(3,5)P]-converting kinases, are male gametophyte lethal in Arabidopsis () due to defective vacuolar fission after pollen mitosis I, suggesting a key role of the phospholipid in dynamic vacuolar organization. However, other genetic components that regulate the production of PI(3,5)P and its involvement in pollen germination and tube growth are unknown. Here, we identified and characterized Arabidopsis VAC14, a homolog of the yeast and metazoan VAC14s that are crucial for the production of PI(3,5)P is constitutively expressed and highly present in developing pollen. Loss of function of was male gametophyte lethal due to defective pollen development. Ultrastructural studies showed that vacuolar fission after pollen mitosis I was compromised in mutant microspores, which led to pollen abortion. We further showed that inhibiting the production of PI(3,5)P or exogenous application of PI(3,5)P mimicked or rescued the pollen developmental defect of the mutant, respectively. Genetic interference and pharmacological approaches suggested a role of PI(3,5)P in pollen germination and tube growth. Our results provide insights into the function of VAC14 and, by inference, that of PI(3,5)P in plant cells.

MYB81, a microspore‐specific GAMYB transcription factor, promotes pollen mitosis I and cell lineage formation in Arabidopsis

“…However, it is unclear whether the persistent central vacuole in scp microspores is the cause or consequence of the delayed division. In a further example that is linked to phosphatidylinositol 3,5‐bisphosphate [PI(3,5)P 2 ] production, mutation of VAC14 , hinders vacuolar fission in microspores and division at PMI leading to pollen abortion (Zhang et al , ). These studies emphasize an important link between the genetic control of vacuolar reorganization and successful transition to PMI.…”

Diverse Physiological Functions of FAB1 and Phosphatidylinositol 3,5-Bisphosphate in Plants

“…FAB1B and FAB1D have complementary roles in the regulation of membrane recycling, vacuolar pH, and the homeostatic ROS control in pollen tube growth, despite the cytosolic localization of FAB1D in the pollen tube (Serrazina et al., 2014). Unlike the gene arrangement of FAB1, Arabidopsis has a single VAC14 gene (Zhang et al., 2018). Bimolecular fluorescence complementation has revealed that FAB1A/B and VAC14 physically interact to form a functional protein complex in Arabidopsis (Whitley et al., 2009; Hirano et al., 2011; Zhang et al., 2018).…”

“…Unlike the gene arrangement of FAB1, Arabidopsis has a single VAC14 gene (Zhang et al., 2018). Bimolecular fluorescence complementation has revealed that FAB1A/B and VAC14 physically interact to form a functional protein complex in Arabidopsis (Whitley et al., 2009; Hirano et al., 2011; Zhang et al., 2018). The Arabidopsis genome includes 9 SAC-domain containing phosphatase (SAC1-SAC9) genes (Zhong and Ye, 2003) which can be separated into three different classes based on their homology; SAC1-SAC5 are the most similar to yeast FIG4p, SAC6-SAC8 have two C-terminal transmembrane domains and are the most similar to yeast SAC1p, and SAC9 is the largest protein containing a unique WW domain (Zhong and Ye, 2003) (Figure 1).…”

“…Loss of VAC14 function leads to a lethal male gametophyte phenotype caused by vacuolar reorganization defects during pollen development (Zhang et al., 2018). A similar male gametophyte phenotype is observed in vac14 and fab1afab1b mutants, and bimolecular fluorescence complementation suggests that FAB1A/B and VAC14 physically interact to form a crucial functional protein complex in Arabidopsis (Whitley et al., 2009; Hirano et al., 2011; Zhang et al., 2018).…”

“…In contrast, gain of function SAC1 mutants have longer root hairs than the wild-type, indicating that SAC1 is essential for elongation during root hair morphogenesis (Vijayakumar et al., 2016). Although a direct interaction between FAB1 and SAC1 has not yet been reported, SAC1 and FAB1B have been found to co-localize in the wortmannin-sensitive vesicles of pollen and pollen tubes (Zhang et al., 2018). These data suggest the formation of a complex between SAC1 and FAB1 in Arabidopsis .…”