Studies on molecular mechanism controlling food preference in Bombyx mori and the related silkmoths and the process of their evolution and domestication of their food

2021 Fiscal Year Final Research Report

• Project/Area Number: 18H03949
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Medium-sized Section 39:Agricultural and environmental biology and related fields
• Research Institution: Gakushuin University
• Principal Investigator: Shimada Toru 学習院大学, 理学部, 教授 (20202111)
• Co-Investigator(Kenkyū-buntansha): 永田 晋治 東京大学, 大学院新領域創成科学研究科, 教授 (40345179)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 食性 / カイコ / エリサン / 感覚神経 / 植物毒素

Outline of Final Research Achievements

Although the silkworm, Bombyx mori, is monophagous to mulberry (Morus spp.), there are polyphagous mutants that can feed on non-mulberry diets. The eri silkworm, Samia ricini, mainly feeds on leaves of castor (Ricinus communis) while the wild species Samia cynthia does on leaves of Ailanthus spp. Genetic studies of the B. mori revealed a responsible gene for the polyphagous trait, and inter-specific hybridization experiments between S. ricini and S. cynthia elucidated that a genomic region potentially controls the resistance to toxicity of castor leaves. Our physio-biochemical analyses indicated that ricinine (a pyridone alkaloid) contained in castor inhibits the larval growth of S. cynthia. RNA-seq analysis revealed that several genes encoding cytochrome P-450, nitrilase, etc. are specifically unregulated in midgut of the larvae fed on castor leaves, suggesting that their gene products contribute to the resistance of S. ricini.

Free Research Field

昆虫遺伝学

Academic Significance and Societal Importance of the Research Achievements

植食性昆虫の多くは単食性または狭食性であり、限られた寄主植物のみを食害する。この昆虫・植物間の関係の特異性は、生態系の成り立ちを理解するために重要なテーマであるとともに、害虫防除や養蚕分野の問題解決に必要な課題でもある。本研究は、植物が食害への防御のために作り出す化合物（毒素）に対して、昆虫がどのような遺伝子を進化させて、それらに対抗してきたか、そのメカニズムの一端を明らかにした。特に、エリサンでは家畜化に伴って食性が大きく変化し、新しい餌であるヒマへの適応を果たしたことを示すとともに、その適応の分子機構の一部を解明した。