Auxin-induced ROS mobilizes intracellular Ca2+ in maize root

Abstract

The natural auxin, IAA (Indole-3-acetic acid) induced H_(2)O_(2) in maize root. When seedlings were incubated in 5μMIAA solution, ROS production was increased and shown maximum content at 60 minutes. The efficient concentration of IAA for the ROS production in Maize root was 5μM. PCIB(α-(p-chlorophenoxy)isobutyric acid), anti auxin, reduced IAA effect on ROS generation. And other synthetic hormones such as 2,4-D(2,4- dichlorophenoxyacetic acid) and α-NAA(α-naphthalene acetic acid) were also induced ROS. However β-NAA(β-naphthalene acetic acid), inactive auxin, did not cause ROS generation meaning that ROS production by IAA is related to functional mechanism. We next asked the signal transduction roles of ROS in response to auxin, intracellular Ca^(2+) mobilization was investigated. When protoplasts were treated with 5μM IAA, intracellular calcium level was increased. Furthermore, scavenging of ROS by the treatment of N-acetyl cystein(NAC) abolished intracellular calcium mobilization. Moreover, as soon as 1mM H_(2)O_(2) was added into protoplasts, intracellular calcium level was promptly raised up. These results indicated that ROS by auxin is essential factor for the intracellular calcium. To identify the ROS target molecules in cells, biotin-labeled iodoacetate (IA) were engaged. Three candidate proteins (70kD, 40kD, and 23kD) are detected in cell. Identification and characterization of ROS target molecules will be elucidated.