Affiliation:
1. Center for Plant Biology, School of Life Sciences Tsinghua University Beijing 100084 China
2. College of Life Sciences Fujian Agriculture and Forestry University Fuzhou Fujian China
3. College of Life Sciences Hebei Normal University Shijiazhuang 050016 China
Abstract
SUMMARYBeing a bona fide actin bundler, Arabidopsis villin5 (VLN5) plays a crucial role in regulating actin stability and organization within pollen tubes. Despite its significance, the precise mechanism through which VLN5 bundles actin filaments has remained elusive. Through meticulous deletion analysis, we have unveiled that the link between gelsolin repeat 6 (G6) and the headpiece domain (VHP), rather than VHP itself, is indispensable for VLN5‐mediated actin bundling. Further refinement of this region has pinpointed a critical sequence spanning from Val763 to Ser823, essential for VLN5's actin‐bundling activity. Notably, the absence of Val763‐Ser823 in VLN5 results in decreased filamentous decoration within pollen tubes and a diminished ability to rescue actin bundling defects in vln2vln5 mutant pollen tubes compared to intact VLN5. Moreover, our findings highlight that the Val763‐Ser823 sequence harbors a binding site for F‐actin, suggesting that this linker‐based F‐actin binding site, in conjunction with the F‐actin binding site localized in G1–G6, enables a single VLN5 to concurrently bind to two adjacent actin filaments. Therefore, our study unveils a novel mechanism by which VLN5 bundles actin filaments.
Funder
National Natural Science Foundation of China
Natural Science Foundation of Fujian Province