Analysis of the mechanism of internal browning of Japanese radish

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K05567
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 39030:Horticultural science-related
• Research Institution: Ishikawa Prefectural University
• Principal Investigator: Fukuoka Nobuyuki 石川県立大学, 生物資源環境学部, 教授 (30502637)
• Co-Investigator(Kenkyū-buntansha): 濱田 達朗 石川県立大学, 生物資源環境学部, 准教授 (50310496)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: Heat stress / Internal browning / Lipid peroxidation / Lipoxygenase / Radish / Reactive oxygen species / Unsaturated fatty acid

Outline of Final Research Achievements

Two types of studies were conducted to clarify the cause of internal browning in radish root. As a result, it was revealed that the occurrence of this disorder is related to ROS production via NADPH-dependent ROS burst and activation of fatty acid degrading enzymes such as lipoxygenase (LOX) induced by high temperature during root maturation stage. A large amount of ROS derived from NADPH-dependent ROS burst and activated LOX act on the unsaturated sites of membrane-constituting fatty acids and induce peroxidation of membrane lipids, thereby inducing membrane collapse. This membrane breakdown causes an enzymatic browning reaction to proceed, leading to damage. The initial hypothesis that advanced glycation end products (AGEs) derived from the Maillard reaction was the main cause of browning was suggested to be AGEs derived from carbonyl compounds generated during the reaction process of membrane lipid peroxidation.

Free Research Field

園芸学

Academic Significance and Societal Importance of the Research Achievements

研究成果は、ダイコン内部褐変症の発生原因を生理学的に究明するものとして、その新規性が認められ国際誌2編に受理された。本研究成果で得られた障害発生の鍵となるNADPH依存性ROSバーストやLOXなどの脂肪酸分解酵素に関わる遺伝子を改変することで、新たな障害抵抗性品種育成の可能性が示唆される。また、生育途中に貯蔵器官の内部が褐変化する障害は、ダイコン以外にもジャガイモ、キャッサバ、ナシ、リンゴなどでもみられ、本研究成果はこれら作物の褐変障害の発生機構を解明する上での基礎的知見ともなり得る。