DIS1 and DIS2 play a role in tropisms in Arabidopsis thaliana

To better understand the role of the cytoskeleton in tropisms, we performed studies of gravitropism and phototropism with seedlings of distorted I (dis1) and distorted2 (dis2) mutants of Arabidopsis thaliana which are defective in the ARP (actin related protein) 2/3 complex. The aim of this investigation was to test the hypothesis that this actin-binding protein family is involved in mechanisms of tropisms in plants. In general, we found that DIS1 has a greater effect on tropisms compared to DIS2. DIS1 enhanced gravitropism in roots of dark-grown seedlings and in inflorescence stems while DIS2 also enhanced gravitropic responses in inflorescences. In contrast, in blue-light-based phototropism, DIS1 attenuated the response in hypocotyls of dark-grown seedlings and in red-light-based positive phototropism in roots. Taken together, these studies are the first to suggest that the ARP 2/3 complex, a major family of actin-binding proteins, is involved in the pathways of gravitropism and phototropism. (C) 2009 Elsevier B.V. All rights reserved.