Evolutionary implications of small RNAs on plant-microbe interactins

2018 Fiscal Year Final Research Report

• Project/Area Number: 17K19269
• 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: Kobe University
• Principal Investigator: NAKAYASHIKI HITOSHI 神戸大学, 農学研究科, 教授 (50252804)
• Research Collaborator: Nguyen Quyet
• Project Period (FY): 2017-06-30 – 2019-03-31
• Keywords: いもち病菌 / 小分子RNA / RNAi

Outline of Final Research Achievements

We performed sRNA sequencing analysis using the Pyricularia oryzae strain Br48 and its gene knock-out (KO) mutants including double dicer- and triple RNA-dependent RNA polymerase (RdRP)-KO mutants. In wild type, approximately 65% of the sRNAs were derived from rRNA and tRNA, and 10% from gene coding and intergenic regions. Several small rRNA sequences, called small rDNA-derived RNAs (srRNAs), exhibited more than 100-fold enrichment in the AGO-libraries relative to the WT library, suggesting a tight association of RNAi with rRNA processing and/or degradation. Consistently, the srRNAs were significantly depleted in the dicer and RdRP KO mutants.
The majority of sRNAs mapped to the gene coding and intergenic regions were not considerably affected by deletion of either dicer or RdRP, suggesting that their biogenesis were dicer- and RdRP-independent. This suggests that significant portions of coding gene-derived sRNAs in the Br48 strain are independent of the canonical RNAi pathways.

Free Research Field

植物病理学

Academic Significance and Societal Importance of the Research Achievements

いもち病菌はイネに甚大な被害を及ぼす植物病原菌であるが、この菌は植物の病害抵抗性を抑止するために、蛋白質や低分子の毒素など、様々な分子を分泌している。近年、これらに加えて小分子RNAを分泌することにより、植物の遺伝子発現をコントロールして病害を発生させる病原菌の例が発見され、本菌においても同様の機構がないのか、また現在ないとしても、今後の進化の過程で獲得する可能性がないのか調査した。