The marvelously diverse Orchidaceae constitutes the largest family of angiosperms. The genus Cymbidium in Orchidaceae is well known for its unique vegetation, floral morphology, and flower scent traits. Here, a chromosome-scale assembly of the genome of Cymbidium ensifolium (Jianlan) is presented. Comparative genomic analysis showed that C. ensifolium has experienced two whole-genome duplication (WGD) events, the most recent of which was shared by all orchids, while the older event was the τ event shared by most monocots. The results of MADS-box genes analysis provided support for establishing a unique gene model of orchid flower development regulation, and flower shape mutations in C. ensifolium were shown to be associated with the abnormal expression of MADS-box genes. The most abundant floral scent components identified included methyl jasmonate, acacia alcohol and linalool, and the genes involved in the floral scent component network of C. ensifolium were determined. Furthermore, the decreased expression of photosynthesis-antennae and photosynthesis metabolic pathway genes in leaves was shown to result in colorful striped leaves, while the increased expression of MADS-box genes in leaves led to perianth-like leaves. Our results provide fundamental insights into orchid evolution and diversification.

中文翻译：

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大花蕙兰基因组揭示了独特形态特征的进化

种类繁多的兰科植物构成了最大的被子植物科。属兰花兰科植物以其独特的植被、花卉形态和花香特征而闻名。在这里，染色体规模的基因组组装大花蕙兰（剑兰）呈现。比较基因组分析表明，C. ensifolium经历了两次全基因组复制（WGD）事件，其中最近一次是所有兰花共有的，而较旧的事件是大多数单子叶植物共有的τ事件。MADS-box基因分析结果为建立独特的兰花发育调控基因模型和兰花花形突变提供了支持。C. ensifolium显示与 MADS-box 基因的异常表达有关。鉴定出的最丰富的花香成分包括茉莉酸甲酯、金合欢醇和芳樟醇，以及参与花香成分网络的基因。C. ensifolium被确定。此外，叶片中光合作用天线和光合作用代谢途径基因的表达降低导致叶片出现彩色条纹，而叶片中 MADS-box 基因表达增加导致叶片呈花被样。我们的结果为兰花进化和多样化提供了基本的见解。