Recombination at apple S locus and molecular evolution of non-self-recognition systems

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K06764
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 45020:Evolutionary biology-related
• Research Institution: Chiba University
• Principal Investigator: KIKUCHI Shinji 千葉大学, 大学院園芸学研究院, 准教授 (80457168)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 自家不和合性 / 遺伝的組換え / 減数分裂 / FISH / 花粉 / ASP-PCR

Outline of Final Research Achievements

Self-incompatibility "S-locus" contains male and female specific genes for self/non-self recognition, which are strongly linked. The aim of this study was to clarify the frequency of recombination in ~1 Mb of the apple S-locus, where there is a cluster of male-specific F-box genes, and to discuss the molecular evolution of male-specific genes in the non-self-recognition system. The BAC-FISH analysis visualized recombination within the apple S-locus during meiosis. Next, DNA was extracted from each pollen grain and genotyped by allele-specific PCR. As a result, pollen with recombinant S-haplotype was found at a lower rate than in meiosis. Further genotyping of the cross seedlings did not reveal any individuals with the recombinant S-haplotype. This potential S-locus recombination may be involved in the creation of S-locus diversity and the maintenance of the non-self-recognition system.

Free Research Field

遺伝育種学、細胞遺伝学

Academic Significance and Societal Importance of the Research Achievements

自家不和合性遺伝子座における雄性側の遺伝子と雌性側の遺伝子は、自他認識システムの崩壊につながるために、それらの間では遺伝的な組換えが抑制されている。しかし、協調的非自己認識システムを持つ植物では、新たに出現した雌性側因子を認識するために、雄性側の因子を多様化し、ハプロイド間で共有する必要がある。これに遺伝的な組換えが必要であると考えた。先行研究と同様、後代で組換えSハプロタイプは見つからなかった（完全連鎖）。一方、減数分裂や花粉で組換えSハプロタイプを発見し、潜在的に自家不和合性遺伝子座内で遺伝的な組換えが起こることを初めて示した。これは、非自己認識機構の分子進化の解明につながる成果と言える。