On April 6th, a research paper entitled "Phosphorylation of OsRbohB by the CaM-dependent protein kinase OsDMI3 promotes H2O2 production to potentiate ABA responses in rice" was published in the prestigious academic journal Molecular Plant (impact factor: 21.949) by Professor Jiang Mingyi's research group from the College of Life Sciences at Nanjing Agricultural University, the National Key Laboratory of Crop Genetic and Germplasm Innovation and Utilization, and the Key Laboratory of Crop Physiology, Ecology, and Production Management of the Ministry of Agriculture and Rural Affairs.
The study highlights the significance of the calcium/calmodulin-dependent protein kinase (CCaMK), which plays a critical role in the signal transduction of the plant hormone abscisic acid (ABA) and abiotic stress. In particular, the CCaMK OsDMI3 in rice has been shown to be a positive regulator of ABA responses, enhancing crop tolerance to drought, salt, and oxidative stress. H2O2 is essential for ABA-induced activation of OsDMI3, as it can oxidize and inactivate the type 2C protein phosphatase (PP2C) OsPP45, thereby relieving the inhibition of OsDMI3 by OsPP45.
The study discovered that ABA induces biphasic H2O2 bursts, and both NADPH oxidases OsRbohB and OsRbohE are involved, with OsRbohB playing a major role, and OsDMI3 only regulating the second-phase extracellular H2O2 burst induced by ABA. It was also demonstrated that OsRbohB is crucial for important physiological processes regulated by ABA, such as seed germination, root growth, stomatal movement, and rice tolerance to water and oxidative stress.
Furthermore, the study found that OsDMI3 can directly interact with OsRbohB and phosphorylate OsRbohB Ser-191, which positively regulates NADPH oxidase activity and H2O2 production in the extracellular space. This enhances rice sensitivity to ABA in seed germination and root growth, as well as rice tolerance to water and oxidative stress. Additionally, the study identified that the rice protein SAPK8/9/10 can regulate ABA-induced biphasic extracellular H2O2 bursts and act upstream of the OsDMI3-OsRbohB pathway in ABA signal transduction.
Overall, this research not only uncovers an important regulatory pathway that directly regulates the activation of NADPH oxidase in ABA signal transduction, but also connects this regulatory pathway to the core pathway of ABA signal transduction. This knowledge could be useful for developing crops that are more resilient to environmental stress, such as drought and oxidative stress.
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