The universal bundling activity of AtVLN4 in diffusely growing cells.

We recently reported that AtVLN4, a member of villin/gelsolin/fragmin superfamily in Arabidopsis thaliana, participated in root hair growth through its actin bundling activity. To further understand the functions of AtVLN4, we investigated its in vivo expression pattern and roles in diffusely growing cells. Transcription analysis of AtVLN4 and detection of AtVLN 4 promoter-GUS activity consistently indicated that AtVLN4 had a universal expression pattern and was preferentially expressed in vegetative tissues. Observation of actin structures labeled by GFP-fABD2 revealed that there were less actin bundles in many diffusely growing cell types in atvln4-1 seedlings than in wild-type seedlings. Pharmacological studies by treatment with Latrunculin B showed that the actin filaments were much easier to be disrupted in diffusely growing cells of atvln4-1 seedlings. Collectively, these results demonstrate that AtVLN4 has a universal actin bundling activity in diffusely growing cells just like that in the tip growing cell, root hairs.