Hidenori Matsui

National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan

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Publications (3)9.96 Total impact

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    ABSTRACT: OsPti1a, an ortholog of tomato SlPti1, functions as a negative regulator of innate immunity in rice (Oryza sativa L.). In ospti1a mutants, the activation of immune responses including HR-like cell death is caused by the loss of OsPti1a protein; however, it is as yet unclear how OsPti1a suppresses immune responses. Here, we report that OsPti1a localizes to detergent-resistant membrane (DRM) fractions of the plasma membrane through lipid modification of the protein's N-terminus, which is highly conserved among Pti1 orthologs in several plant species. Importantly, mis-localization of OsPti1a after deletion of its N-terminus reduced its ability to complement the mutant phenotypes including HR-like cell death. Further, complex formation of OsPti1a depends on its N terminus-mediated membrane localization. LC-MS/MS analysis of OsPti1a complex-interacting proteins identified several defense-related proteins. Collectively, these findings indicate that appropriate complex formation by OsPti1a at the plasma membrane is required for negative regulation of plant immune responses in rice.
    Plant physiology. 06/2014;
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    ABSTRACT: The AGC kinase OsOxi1, which has been isolated as an interactor with OsPti1a, positively regulates basal disease resistance in rice. In eukaryotes, AGC kinase family proteins are regulated by 3-phosphoinositide-dependent protein kinase 1 (Pdk1). In Arabidopsis, AtPdk1 directly interacts with phosphatidic acid, which functions as a second messenger in both biotic and abiotic stress responses. However, the functions of Pdk1 are poorly understood in plants. We show here that OsPdk1 acts upstream of the OsOxi1-OsPti1a signal cascade in disease resistance in rice. OsPdk1 interacts with OsOxi1 and phosphorylates the Ser283 residue of OsOxi1 in vitro. To investigate whether OsPdk1 is involved in immunity that is triggered by microbial-associated molecular patterns, we analyzed the phosphorylation status of OsPdk1 in response to chitin elicitor. Like OsOxi1, OsPdk1 is rapidly phosphorylated in response to chitin elicitor, suggesting that OsPdk1 participates in signal transduction through pathogen recognition. The overexpression of OsPdk1 enhanced basal resistance against a blast fungus, Magnaporthe oryzae, and a bacterial pathogen, Xanthomonas oryzae pv. oryzae (Xoo). Taken together, these results suggest that OsPdk1 positively regulates basal disease resistance through the OsOxi1-OsPti1a phosphorylation cascade in rice.
    Plant and Cell Physiology 11/2010; 51(12):2082-91. · 4.98 Impact Factor
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    ABSTRACT: OsPti1a, a functional ortholog of tomato SlPti1, negatively regulates both basal resistance and R-gene-mediated resistance in rice. To investigate the molecular function of OsPti1a in defense responses, we searched for components interacting with OsPti1a using a yeast two-hybrid system. One of the interacting proteins is a Ser/Thr kinase that directly phosphorylates OsPti1a in vitro. This protein belongs to the AGC kinase family and is highly similar to AtOxi1, which is induced in response to a wide range of reactive oxygen species (ROS)-generating stimuli in Arabidopsis. Thus, it was designated OsOxi1. OsOxi1 was transiently phosphorylated in response to ROS and chitin elicitor. Both OsOxi1-overexpressing transgenic lines and the ospti1a mutant were highly sensitive to ROS treatment, indicating that OsOxi1 and OsPti1a are involved in ROS-mediated signaling in opposing ways. OsOxi1 is specifically expressed at infection sites where ROS are produced after inoculation with a blast fungus, Magnaporthe oryzae. Overexpression of OsOxi1 enhanced basal resistance to the blast fungus, indicating that OsOxi1 positively regulates disease resistance. OsOxi1 phosphorylates Thr-233 of OsPti1a and a point mutation of Thr-233 enhanced disease susceptibility to a bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo), suggesting that the phosphorylation of OsPti1a by OsOxi1 is essential for basal resistance to Xoo. Taken together, our data suggest that OsOxi1 positively regulates defense responses through the phosphorylation of OsPti1a, causing the release from an OsPti1a-dependent inhibition of the responses.
    Plant and Cell Physiology 10/2010; 51(10):1731-44. · 4.98 Impact Factor