Li Xinlei, Fan Zhengqi, Guo Haobo, Ye Ning, Lyu Tao, Yang Wen, Wang Jie, Wang Jia-Tong, Wu Bin, Li Jiyuan, Yin Hengfu
State Key Laboratory of Tree Genetics and Breeding, Research Institute of Subtropical Forestry, Chinese Academy of Forestry, Fuyang, Zhejiang, 311400, China.
Key Laboratory of Forest Genetics and Breeding, Chinese Academy of Forestry, Fuyang, Zhejiang, 311400, China.
Funct Integr Genomics. 2018 Nov;18(6):659-671. doi: 10.1007/s10142-018-0617-9. Epub 2018 Jun 12.
Yellow-flowering species are unique in the genus Camellia not only for their bright yellow pigments but also the health-improving substances in petals. However, little is known regarding the biosynthesis pathways of pigments and secondary metabolites. Here, we performed comparative genomics studies in two yellow-flowered species of the genus Camellia with distinctive flowering periods. We obtained 112,190 and 89,609 unigenes from Camellia nitidissima and Camellia chuongtsoensis, respectively, and identified 9547 gene family clusters shared with various plant species and 3414 single-copy gene families. Global gene expression analysis revealed six comparisons of differentially expressed gene sets in different developmental stages of floral bud. Through the identification of orthologous pairs, conserved and specific differentially expressed genes (DEGs) between species were compared. Functional enrichment analysis suggested that the gibberellin (GA) biosynthesis pathway might be related to the alteration of flowering responses. Furthermore, the expression patterns of secondary metabolism pathway genes were analyzed between yellow- and red-flowered Camellias. We showed that the key enzymes involved in glycosylation of flavonoids displayed differential expression patterns, indicating that the direct glycosylation of flavonols rather than anthocyanins was pivotal to coloration and health-improving metabolites in the yellow Camellia petals. Finally, the gene family analysis of UDP-glycosyltransferases revealed an expansion of group C members in C. nitidissima. Through comparative genomics analysis, we demonstrate that changes of gene expression and gene family members are critical to the variation of natural traits. This work provides valuable insights into the molecular regulation of trait adaptations of floral pigmentation and flowering timing.
黄花物种在山茶属中独具特色，不仅因其明亮的黄色色素，还因其花瓣中含有的有益健康的物质。然而，关于色素和次生代谢产物的生物合成途径，我们所知甚少。在此，我们对山茶属中两个花期不同的黄花物种进行了比较基因组学研究。我们分别从金花茶和长柱红山茶中获得了112,190个和89,609个单基因，并鉴定出与多种植物物种共有的9547个基因家族簇和3414个单拷贝基因家族。全基因组表达分析揭示了花芽不同发育阶段差异表达基因集的六组比较。通过直系同源对的鉴定，比较了物种间保守和特异的差异表达基因（DEG）。功能富集分析表明，赤霉素（GA）生物合成途径可能与开花反应的改变有关。此外，我们还分析了黄花和红花山茶之间次生代谢途径基因的表达模式。我们发现，参与黄酮类糖基化的关键酶呈现出不同的表达模式，这表明黄酮醇而非花青素的直接糖基化对于黄花山茶花瓣的着色和有益健康的代谢产物至关重要。最后，UDP-糖基转移酶的基因家族分析显示，金花茶中C组成员有所扩增。通过比较基因组学分析，我们证明基因表达和基因家族成员的变化对于自然性状的变异至关重要。这项工作为花卉色素沉着和开花时间性状适应的分子调控提供了有价值的见解。
