2025-09-14 中国科学院(CAS)
中国科学院華南植物園と山東理工大学の研究チームは、四倍体植物Schizomussaenda henryiのゲノム解析により、多型花現象「異型花柱性」が多倍体化後も維持されていることを発見した。通常、全ゲノム重複は複雑な遺伝システムを崩壊させ、同型花柱性に移行すると考えられてきたが、本研究はその常識を覆した。研究チームは本種で初の染色体レベルのゲノムを組み立て、S遺伝子座が短花柱型個体にのみ存在し、4つの連鎖遺伝子を含むことを解明。その中でSchzAUX22が異型花柱性の主要制御因子とされた。系統解析では、約3.6百万年前に異種倍数化で本種が誕生し、S遺伝子座自体は約5000万年前に出現したと推定された。成果は多倍体植物の繁殖進化や花の多様性理解に新たな視点を与えるもので、『New Phytologist』に掲載された。
A. The L-morph and S-morph flowers ofSchizomussaenda henryi. B. Circos map illustrating basic information on the S. henryi genome (S-morph). C. Model of the genomic structure of S-locus genes in S. henryi. D. Ks distributions of paralogous genes in S. henryi (S-morph), Mussaenda pubescens, Coffea canephora (Rubiaceae) and Thymus quinquecostatus (Lamiaceae). (Image by SHI Miaomiao et al)
<関連情報>
- https://english.cas.cn/newsroom/research_news/life/202509/t20250915_1054668.shtml
- https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.70521
四倍体雌雄異株種におけるS遺伝子座スーパー遺伝子の遺伝的構造解明 Genetic architecture of the S-locus supergene revealed in a tetraploid distylous species
Zhonglai Luo, Spencer C. H. Barrett, Tieyao Tu, Zhongtao Zhao, Shanshan Jia, Shiran Gu, Tingting Duan, Yu Zhang, Bingqiang Xu, Lei Gu, Xiaofang Deng …
New Phytologist Published: 05 September 2025
DOI:https://doi.org/10.1111/nph.70521
Summary
- Heterostyly is a polymorphic floral adaptation controlled by supergenes. The molecular basis of distyly has been investigated in diploid species from several unrelated families, but information is lacking for polyploid systems.
- Here, we address this knowledge gap in Schizomussaenda henryi, a tetraploid distylous species of Rubiaceae, the family with the greatest number of heterostylous species. Using chromosome-level genome assemblies and transcriptome profiling, we characterized its tetraploid genome, identified the S-locus region, and performed evolutionary analysis.
- The S-locus contains four hemizygous genes in the S-morph. SchzAUX22 emerged as a candidate gene potentially regulating both style length and filament growth via auxin signaling. Phylogenetic and k-mer-based analysis suggested a hybrid allopolyploid origin for S. henryi, while no subgenome dominance was detected. Results from the comparison of Ks values indicated that S-locus formation likely occurred through stepwise duplications.
- This study provides the first comprehensive genomic analysis of distyly in a polyploid species and demonstrates that the S-locus remains intact despite allopolyploidization resulting from hybridization. Our results indicated that polyploidization does not necessitate the breakdown of distyly, which occurs in several other heterostylous lineages.
