Functional Characterization of PeVLN4 Involved in Regulating Pollen Tube Growth from Passion Fruit

Passion fruit (<i>Passiflora edulis</i>), mainly distributed in tropical and subtropical regions, is popular for its unique flavor and health benefits. The actin cytoskeleton plays a crucial role in plant growth and development, and villin is a key regulator of actin dynamics. However, the mechanism underlying the actin filament regulation of reproductive development in passion fruit remains poorly understood. Here, we characterized a villin isovariant in passion fruit, <i>Passiflora edulis VLN4</i> (<i>PeVLN4</i>), highly and preferentially expressed in pollen. Subcellular localization analysis showed that PeVLN4 decorated distinct filamentous structures in pollen tubes. We next introduced <i>PeVLN4</i> into <i>Arabidopsis villin</i> mutants to explore its functions on the growing pollen tubes. <i>PeVLN4</i> rescued defects in the elongation of <i>villin</i> mutant pollen tubes. Pollen tubes expressing <i>PeVLN4</i> were revealed to be less sensitive to latrunculin B, and <i>PeVLN4</i> partially rescued defects in the actin filament organization of <i>villin</i> mutant pollen tubes. Additionally, biochemical assays revealed that PeVLN4 bundles actin filaments in vitro. Thus, PeVLN4 is an important regulator of F-actin stability and is required for normal pollen tube growth in passion fruit. This study provides a new insight into the function of the actin regulator villin involved in the reproduction development of passion fruit.