Arabidopsis thalianasubclass I ACTIN DEPOLYMERIZING FACTORs regulate nuclear organization and gene expression

Abstract

ABSTRACTACTIN DEPOLYMERIZING FACTOR (ADF) is a conserved protein that regulates the organization and dynamics of actin microfilaments. Eleven ADFs in theArabidopsis thalianagenome are grouped into four subclasses, and subclass I ADFs, ADF1–4, are all expressed throughout the plant. Previously, we showed that subclass I ADFs function in the regulation of the response against powdery mildew fungus as well as in the regulation of cell size and endoreplication. Here, we report a new role of subclass I ADFs in the regulation of nuclear organization and gene expression. Through a microscopic observation of epidermal cells in mature leaves, we found that the size of chromocenters in bothadf4and transgenic lines where expression of subclass IADFs are downregulated (ADF1-4Ri) was reduced compared with that of wild-type Col-0.A. thalianapossesses eightACTINgenes, among whichACT2,-7, and-8are expressed in vegetative organs. The chromocenter size inact7, but not in theact2/8double mutant, was enlarged compared with that in Col-0. Microarray analysis revealed that 1,818 genes were differentially expressed inadf4andADF1-4Ri. In particular, expression of 22 nucleotide-binding leucine-rich repeat (NLR) genes, which are involved in effector-triggered plant immunity, was reduced inadf4andADF1-4Ri. qRT-PCR confirmed the altered expressions shown with microarray analysis. Overall, these results suggest that ADF regulates various aspects of plant physiology through its role in regulation of nuclear organization and gene expression. The mechanism how ADF and ACTIN regulate nuclear organization and gene expression is discussed.