铁皮石斛(Dendrobium catenatum)叶艺形成机制的初探

目的]探究铁皮石斛(Dendrobium catenatum)叶艺形成的分子机制,为培育叶艺兰花品种提供理论基础。方法]以正常铁皮石斛(WT)、叶艺铁皮石斛叶片绿色组织(YYG)、叶艺铁皮石斛叶艺白色组织(YYW)为研究对象,通过显微结构观察、叶绿素及其前体物质含量的测定、叶绿素合成相关基因的qRTPCR定量来探究叶艺形成的分子机制。结果]YYW的总叶绿素含量明显低于WT和YYG,同时其叶绿体细胞结构出现了畸形现象。在叶绿素合成前体物质中,YYW中粪卟啉原Ⅲ的含量显著高于WT和YYG,而原卟啉IX、镁原卟啉IX和原叶绿素酸酯在WT和YYG中的含量则高于YYW。此外,qRT-PCR结果显示:粪卟啉原氧化脱羧酶(DcHEMF)、原卟啉原氧化酶(DcHEMG)、镁螯合酶H亚基(DcCHLH)在YYW中的表达量显著下调。结论]YYW中DcHEMF、DcHEMG和DcCHLH表达量的下调使粪卟啉原Ⅲ无法正常流向叶绿素合成,这导致了其叶绿素含量的下降,是使铁皮石斛叶片出现了叶艺表型的主要原因。

A Preliminary Study of Yeyi Mechanism in Dendrobium catenatum Leaves

Objective] To find the mechanism of Yeyi(a mutation of de-greening) of Dendrobium catenatum leaves and provide information for breeding novel orchid cultivar. Method] The normal D. catenatum leaf(WT), the green parts of mutant leaf(YYG) and the white parts of mutant leaf(YYW) were used to study the molecular mechanism of Yeyi formation by observing the microstructure, the quantification of chlorophyll and its precursor, and the quantitative real-time PCR(qRT-PCR) of chlorophyll biosynthesis related genes. Result] There was almost no green cell and the cellular structure of chloroplasts appeared abnormal in YYW. Among the precursors of chlorophyll, the coproporphyrinogen Ⅲ content in YYW was significant lower than that in WT and YYG, whereas the contents of protoporphyrin IX, Mg-Protoporphyrin IX and Protochlorophyllide in WT and YYG were higher than that in YYW. In addition, the qRT-PCR result suggested that the expressional levels of DcHEMF, DcHEMG, and DcCHLH were significantly down-regulated in YYW. Conclusion] The down-regulated expression of DcHEMF, DcHEMG, and DcCHLH prevents coproporphyrinogen Ⅲ from flowing into chlorophyll biosynthesis in YYW, which will lead to the decrease of chlorophyll content and is the main reason for appearing the phenotype of Yeyi in D. catenatum.