Analysis of flower type formation mechanism in chrysanthemum

2020 Fiscal Year Final Research Report

• Project/Area Number: 17H03762
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Horticultural science
• Research Institution: The University of Tokyo
• Principal Investigator: SHIBATA Michio 東京大学, 大学院農学生命科学研究科(農学部), 教授 (80355718)
• Co-Investigator(Kenkyū-buntansha): 樋口 洋平 東京大学, 大学院農学生命科学研究科(農学部), 准教授 (00746844)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Keywords: 遺伝子 / 花型 / 頭状花序 / 八重咲き

Outline of Final Research Achievements

Seven CYC2 genes, which had been reported to be involved in ray floret formation in Senecio vulgaris, were isolated from a diploid wild species of Chrysanthemum, Chrysanthemum seticuspe. Spatiotemporal expression analyses of three CYC2 genes with high expression levels in the early stage of capitulum development showed that CYC2 genes were expressed in stamens and pistils of disc florets, as well as petals of ray florets. Gene knock-out by CRISPR/Cas9 genome editing system targeting CYC2 gene resulted in multiple transformants lacking several bases within the target site of CYC2 gene, and phenotypic analysis of these transformants showed a tendency for ray florets to be converted to disc florets. The results of gene disruption by genome editing also suggested that the CYC2 gene is involved in florets formation not only in ray florets but also in disc florets.

Free Research Field

園芸科学

Academic Significance and Societal Importance of the Research Achievements

花きでは一般に一重咲きに比べて八重咲きの観賞価値が高い。八重咲きはABCクラス遺伝子の変異によるとの報告があるが、キク科の花は舌状花と筒状花からなる頭状花序を形成していることから、八重咲きのメカニズムは異なると推定される。近年、キク科における筒状花から舌状花への分化を制御する候補遺伝子としてCYC2が注目されてきたが、本研究では、キク科花きで最も重要なキク属のキクタニギクで初めて内在遺伝子破壊に成功し、CYC2遺伝子が舌状花アイデンティティの獲得のみならず筒状花形成にも関与することを明らかにできた。今後の栽培ギクの品種改良にとっても有用な成果である。