| Budget Amount *help |
¥4,680,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥1,080,000)
Fiscal Year 2012: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2011: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
Fiscal Year 2010: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
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| Research Abstract |
Hormone crosstalk is pivotal in plant.pathogen interactions. In this study, we found that blast infection to rice seedlings lead to massive accumulation of N^6-(Δ^2-isopentenyl) adenine (iP), iP riboside (iPR) and iPR 5′-phosphates (iPRP) in leaf blades. Consistent with this, cytokinin (CK) signaling was activated around the infection sites as shown by histochemical staining for β-glucuronidase activity driven by a CK-responsive OsRR6 promoter. A diverse CK species were also detected in the hyphae (mycelium), conidia and culture filtrates of blast fungus, indicating that M. oryzae is capable of production, as well as hyphal secretion of CKs. Co-treatment of leaf blades with CK and salicylic acid (SA), but not with either one alone, markedly induced pathogenesis-related genes OsPR1b and PBZ1 (probenazole-induced protein 1). These effects were diminished by RNAi-knockdown of OsNPR1 or WRKY45, the key regulators of SA signaling pathway in rice, indicating that the effects of CKs depend on these two regulators. Taken together, our data imply a coevolutionary rice.M. oryzae interaction, wherein M. oryzae probably elevates rice CK levels for its own benefits such as nutrient translocation. Rice plants, on the other hand, sense it as an infection signal and activate defense reactions through the synergistic action with SA.
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