Hu Zenghui, Tang Biao, Wu Qi, Zheng Jian, Leng Pingsheng, Zhang Kezhong
College of Landscape Architecture, Beijing University of AgricultureBeijing, China.
Beijing Collaborative Innovation Center for Eco-environmental Improvement with Forestry and Fruit TreesBeijing, China.
Front Plant Sci. 2017 Aug 4;8:1351. doi: 10.3389/fpls.2017.01351. eCollection 2017.
is a world famous fragrant bulb flower with high ornamental and economic values, and significant differences in fragrance are found among different genotypes. In order to explore the mechanism underlying the different fragrances, the floral scents of 'Sibeia', with a strong fragrance, and 'Novano', with a very faint fragrance, were collected using a dynamic headspace technique. These scents were identified using automated thermal desorption-gas chromatography/mass spectrometry (ATD-GC/MS) at different flowering stages. We used RNA-Seq technique to determine the petal transcriptome at the full-bloom stage and analyzed differentially expressed genes (DEGs) to investigate the molecular mechanism of floral scent biosynthesis. The results showed that a significantly higher amount of 'Siberia' floral scent was released compared with 'Novano'. Moreover, monoterpenes played a dominant role in the floral scent of 'Siberia'; therefore, it is believed that the different emissions of monoterpenes mainly contributed to the difference in the floral scent between the two genotypes. Transcriptome sequencing analysis indicated that ~29.24 Gb of raw data were generated and assembled into 124,233 unigenes, of which 35,749 unigenes were annotated. Through a comparison of gene expression between these two genotypes, 6,496 DEGs were identified. The genes in the terpenoid backbone biosynthesis pathway showed significantly different expression levels. The gene expressions of 1-deoxy-D-xylulose 5-phosphate synthase (DXS), 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR), 4-hydroxy-3-methylbut-2-enyl diphosphate synthase (HDS), 4-hydroxy-3-methylbut-2-enyl diphosphate reductase (HDR), isopentenyl diphosphate isomerase (IDI), and geranyl diphosphate synthase (GPS/GGPS), were upregulated in 'Siberia' compared to 'Novano', and two monoterpene synthase genes, ocimene synthase gene () and myrcene synthase gene (), were also expressed at higher levels in the tepals of 'Siberia', which was consistent with the monoterpene release amounts. We demonstrated that the high activation levels of the pathways contributed to monoterpene biosynthesis in 'Siberia' resulting in high accumulations and emissions of monoterpenes, which led to the difference in fragrance between these two genotypes.
是一种世界著名的香鳞茎花卉，具有很高的观赏和经济价值，不同基因型之间的香味存在显著差异。为了探究不同香味的潜在机制，采用动态顶空技术收集了香味浓郁的‘西伯利亚’和香味极淡的‘诺瓦诺’的花香。在不同开花阶段，使用自动热解吸-气相色谱/质谱联用仪（ATD-GC/MS）对这些花香进行鉴定。我们利用RNA测序技术测定了盛花期花瓣转录组，并分析差异表达基因（DEGs）以研究花香生物合成的分子机制。结果表明，与‘诺瓦诺’相比，‘西伯利亚’释放的花香量显著更高。此外，单萜类化合物在‘西伯利亚’的花香中起主导作用；因此，认为单萜类化合物的不同释放量主要导致了这两个基因型之间花香的差异。转录组测序分析表明，产生了约29.24 Gb的原始数据，并组装成124,233个单基因，其中35,749个单基因得到注释。通过比较这两个基因型之间的基因表达，鉴定出6,496个差异表达基因。萜类骨架生物合成途径中的基因表达水平存在显著差异。与‘诺瓦诺’相比，1-脱氧-D-木酮糖-5-磷酸合酶（DXS）、1-脱氧-D-木酮糖-5-磷酸还原异构酶（DXR）、4-羟基-3-甲基丁-2-烯基二磷酸合酶（HDS）、4-羟基-3-甲基丁-2-烯基二磷酸还原酶（HDR）、异戊烯基二磷酸异构酶（IDI）和香叶基二磷酸合酶（GPS/GGPS）在‘西伯利亚’中上调，并且两个单萜合酶基因，罗勒烯合酶基因（）和月桂烯合酶基因（）在‘西伯利亚’的花被片中也有较高水平的表达，这与单萜类化合物的释放量一致。我们证明，这些途径的高激活水平有助于‘西伯利亚’中单萜类化合物的生物合成，导致单萜类化合物的高积累和释放，从而导致这两个基因型之间的香味差异。
