Yang Xia, Liu Qi, Wang Miao-Miao, Wang Xiao-Ya, Han Meng-Qi, Liu Fang-Pu, Lü Tian-Feng, Liu Jing, Wang Yin-Zheng
Key Laboratory of Plant Diversity and Specialty Crops, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
China National Botanical Garden (South Garden), Beijing 100093, China.
Plant Cell. 2024 Dec 23;37(1). doi: 10.1093/plcell/koae283.
Plants bearing double flowers have long been cultivated as ornamental plants. Hose-in-hose flowers, bearing two-whorled corolla tubes in whorls 1 and 2, are uncommon but recur in Sinningia (Gesnerioideae, Gesneriaceae). In this study, we selected 15 hose-in-hose cultivars as materials to explore the underlying molecular and genetic mechanisms of this floral architecture. We found that they originated from different hybridization events within the Dircaea clade. Three B-class MADS-box genes were globally expressed in all floral whorls, but only GLOBOSA1 (GLO1) has accumulated a dominant mutation, i.e. the insertion of a hAT-like miniature inverted-repeat transposable element (MITE) into its promoter, that co-segregated with the hose-in-hose phenotype. In addition, all 15 hose-in-hose cultivars contained the same dominant GLO1 allele. Transient gene expression assays confirmed the role of this MITE insertion in upregulating the promoter activity of GLO1 by providing several cis-regulatory elements. Genetic transformation in heterologous Chirita pumila (Didymocarpoideae, Gesneriaceae) verified that this dominant GLO1 allele is sufficient to confer the hose-in-hose phenotype. We further demonstrated that both the GLO1 allele and the hAT-like MITE descended from wild S. cardinalis with single flowers. This study highlights the significance of wide hybridization in frequent gains of the dominant GLO1 allele and thereafter repeated occurrence of hose-in-hose flowers in Sinningia.
重瓣花植物长期以来一直作为观赏植物进行栽培。套鞘花在第1轮和第2轮中有两轮花冠管，较为罕见，但在大岩桐属（苦苣苔科，大岩桐亚科）中会反复出现。在本研究中，我们选择了15个套鞘花品种作为材料，以探究这种花部结构潜在的分子和遗传机制。我们发现它们起源于Dircaea分支内不同的杂交事件。三个B类MADS盒基因在所有花轮中均有全局表达，但只有球状花1（GLO1）积累了一个显性突变，即一个类hAT微型反向重复转座元件（MITE）插入其启动子，该突变与套鞘花表型共分离。此外，所有15个套鞘花品种都含有相同的显性GLO1等位基因。瞬时基因表达分析通过提供几个顺式调控元件，证实了该MITE插入在上调GLO1启动子活性中的作用。在异源植物石蝴蝶（苦苣苔科，石蝴蝶亚科）中的遗传转化证实，这种显性GLO1等位基因足以赋予套鞘花表型。我们进一步证明，GLO1等位基因和类hAT MITE均源自具有单花的野生红花大岩桐。本研究强调了远缘杂交在大岩桐属中频繁获得显性GLO1等位基因以及随后套鞘花反复出现中的重要性。
