Protein phosphorylation is a prerequisite for the Ca²⁺-dependent activation of Arabidopsis NADPH oxidases and may function as a trigger for the positive feedback regulation of Ca²⁺ and reactive oxygen species

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• 作者：Sachie Kimura¹ ; Hidetaka Kaya¹ ; Tomoko Kawarazaki ; Goro Hiraoka ; Eriko Senzaki ; Masataka Michikawa ; Kazuyuki Kuchitsu ; ^{kuchitsu@rs.noda.tus.ac.jp}
• 关键词：AtRbohD ; AtRbohF ; Ca2+ ; Positive feedback regulation ; Protein phosphorylation ; Reactive oxygen species (ROS)
• 刊名：Biochimica et Biophysica Acta (BBA)/Molecular Cell Research
• 出版年：2012
• 出版时间：February 2012
• 年：2012
• 卷：1823
• 期：2
• 页码：398-405
• 全文大小：1028 K

文摘

Reactive oxygen species (ROS) produced by NADPH oxidases play critical roles in signalling and development. Given the high toxicity of ROS, their production is tightly regulated. In Arabidopsis, respiratory burst oxidase homologue F (AtrbohF) encodes NADPH oxidase. Here we characterised the activation of AtRbohF using a heterologous expression system. AtRbohF exhibited ROS-producing activity that was synergistically activated by protein phosphorylation and Ca²⁺. The two EF-hand motifs of AtRbohF in the N-terminal cytosolic region were crucial for its Ca²⁺-dependent activation. AtrbohD and AtrbohF are involved in stress responses. Although the activation mechanisms for AtRbohD and AtRbohF were similar, AtRbohD had significantly greater ROS-producing activity than AtRbohF, which may reflect their functional diversity, at least in part. We further characterised the interrelationship between Ca²⁺ and phosphorylation regarding activation and found that protein phosphorylation-induced activation was independent of Ca²⁺. In contrast, K-252a, a protein kinase inhibitor, inhibited the Ca²⁺-dependent ROS-producing activity of AtRbohD and AtRbohF in a dose-dependent manner, suggesting that protein phosphorylation is a prerequisite for the Ca²⁺-dependent activation of Rboh. Positive feedback regulation of Ca²⁺ and ROS through AtRbohC has been proposed to play a critical role in root hair tip growth. Our findings suggest that Rboh phosphorylation is the initial trigger for the plant Ca²⁺-ROS signalling network.