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

Passion fruit (Passiflora edulis), 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, Passiflora edulis VLN4 (PeVLN4), highly and preferentially expressed in pollen. Subcellular localization analysis showed that PeVLN4 decorated distinct filamentous structures in pollen tubes. We next introduced PeVLN4 into Arabidopsis villin mutants to explore its functions on the growing pollen tubes. PeVLN4 rescued defects in the elongation of villin mutant pollen tubes. Pollen tubes expressing PeVLN4 were revealed to be less sensitive to latrunculin B, and PeVLN4 partially rescued defects in the actin filament organization of villin 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.