Arabidopsis actin capping protein (AtCP) subunits have different expression patterns, and downregulation of AtCPB confers increased thermotolerance of Arabidopsis after heat shock stress

As a heterodimer actin-binding protein, capping protein is composed of alpha and beta subunits, and can stabilize the actin filament cytoskeleton by binding to F-actin ends to inhibit G-actin addition or loss from that end. Until now, studies on plant capping protein have focused on biochemical functions in vitro, and so the expression patterns and physiological functions of actin capping protein in Arabidopsis (AtCP) are poorly understood. In the present study, real-time quantitative PCR and Western blot analysis showed that although AtCP alpha and beta subunits (i.e. AtCPA and AtCPB) were expressed in various tissues, their expression patterns were significantly different. GUS staining further indicated they were present in different parts of the same organs. We also demonstrated that the expression levels of both subunits were induced by heat shock stress. However, only the atcp beta-mutant showed enhanced thermotolerance, and confocal microscopy showed that the actin filaments of the atcp beta-mutant were much more complete than that in the wild-type and the atcp alpha-mutant after heat treatment at 45 degrees C for 40 and 45 min. In conclusion, these results demonstrated that AtCPA and AtCPB showed distinct expression patterns in vivo, and that downregulation of AtCPB conferred increased plant thermotolerance after heat shock stress. (C) 2012 Elsevier Ireland Ltd. All rights reserved.