Enhanced virulence induced by coinfection with plant virus and bacteria

Research Project

Project/Area Number	17K19263
Research Category	Grant-in-Aid for Challenging Research (Exploratory)
Allocation Type	Multi-year Fund
Research Field	Agricultural and Environmental Biology and related fields
Research Institution	Shizuoka University
Principal Investigator	Hirata Hisae 静岡大学, 農学部, 准教授 (00432196)
Project Period (FY)	2017-06-30 – 2020-03-31
Project Status	Completed (Fiscal Year 2019)
Budget Amount *help	¥6,110,000 (Direct Cost: ¥4,700,000、Indirect Cost: ¥1,410,000) Fiscal Year 2019: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000) Fiscal Year 2018: ¥2,470,000 (Direct Cost: ¥1,900,000、Indirect Cost: ¥570,000) Fiscal Year 2017: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000)
Keywords	カンキツ / ウイルス / 細菌 / 細菌病 / ウイルス病 / 病原性
Outline of Final Research Achievements	To understand the influence of coinfection with a plant virus and a plant pathogenic bacterium, Xanthomonas citri pv. citri (Xcc) was inoculated to leaves of citrus plants infected with Apple stem grooving virus and to leaves of uninfected plants. After inoculation with Xcc, the population of Xcc and the size of citrus canker lesions on ASGV-infected leaves were larger than those on ASGV-uninfected leaves. Expression of genes related to canker formation was highly upregulated and that of genes related to plant defense responses was repressed after coinoculation with ASGV and Xcc, relative to Xcc alone, suggesting that the defense response against Xcc was suppressed by ASGV infection.
Academic Significance and Societal Importance of the Research Achievements	従来の重複感染の研究は、病原性が弱い系統や、非病原性系等を用いた近縁種を用いた交叉反応による生物的防除法を目的とした例が多く、異種病原体の重複感染に関する知見は限られていた。本研究では、研究材料としては例が少ない果樹のカンキツをモデルに、病原細菌と病原ウイルスの重複感染の実験系を立ち上げ、ウイルス感染が細菌病の発病を促進することを示した。永年生の果樹では潜在感染するウイルスも多く報告されており、植物病の診断では病原性の変化により特定が難しい事例もある。重複感染が病徴発現に影響を及ぼすことが具体的に示されたことで、ターゲットを広げた病害管理の重要性を示すことができた。