Analysis of defense responses based on innate immunity against viroid infection and mechanism to develop dwarfing and necrosis

2020 Fiscal Year Final Research Report

• Project/Area Number: 18H02201
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 39040:Plant protection science-related
• Research Institution: Hirosaki University
• Principal Investigator: Sano Teruo 弘前大学, 農学生命科学部, 教授 (30142699)
• Co-Investigator(Kenkyū-buntansha): 葛西 厚史 弘前大学, 農学生命科学部, 研究機関研究員 (80633982) ; 中原 健二 北海道大学, 農学研究院, 講師 (90315606)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: ウイロイド / 自然免疫 / 矮化 / 壊疽 / 活性酸素種（ROS) / miR398 / miR398a-3p / 2-オキソグルタル酸ジオキシゲナーゼ

Outline of Final Research Achievements

In tomato plants infected with the virulent strain of potato spindle tuber viroid (PSTVd), stress-responsive microRNAs (miR398 and miR398a-3p) were excessively induced, and the expression of SOD genes encoding reactive oxygen species (ROS) scavenging enzymes were down-regulated, which caused loss of normal ROS scavenging function resulted in excessive accumulation of ROS, leading to severe pathological symptoms accompanied by necrosis. The nucleotides at position 42 and 64 of the attenuated strain of PSTVd were key nucleotides for the attenuation, and in cooperation with the nucleotides 43, 310, and 311/312, contributed to its low and stable accumulation. The attenuated strain did not elicit an excessive defense responses, such as pathogenesis-related protein 1b1. A novel 2-oxoglutarate Fe (II)-dependent oxygenase gene associated with dwarfing and leaf malformation characteristic of viroid disease was identified in tomato plant (Solanum lycopersicum).

Free Research Field

植物保護科学関連

Academic Significance and Societal Importance of the Research Achievements

ウイロイドは小環状1本鎖RNA病原体で、侵入した宿主細胞中で自己増殖し、矮化・葉巻・壊疽・塊茎/果実の肥大異常や着色障害を起こす。ジャガイモ、トマト、キク、ココヤシ、ホップ、リンゴなど様々な農作物に経済的被害を与えている。治療薬はなく、診断により早期に発見して除去する以外に有効な防除方法がない。本研究では、ウイロイド感染に対する宿主の基礎的自然免疫で生じる抵抗性反応、特に活性酸素種の発生機構とそれがウイロイド特有の病徴発現に至る分子機構の一端を明らかした。これらの研究成果は、植物本来の自然免疫を活用した実用的ウイロイド防御戦略の開発に貢献するものである。