杂交兰花色花香生物合成途径的转录组分析

Transcriptome Analysis of Pigment Biosynthesis and Floral Scent Biosynthesis in Cymbidium Hybrid

该研究以杂交兰(Cymbidium hybrid)不同花色花香品种‘玉凤’(K18,黄色)和‘福韵丹霞’(K24,紫红色)为材料,采用RNA-Seq技术获得杂交兰不同花期的花朵转录组数据,分析杂交兰不同时期花色/花香相关基因的表达变化,探讨杂交兰花色花香形成的分子机理,为杂交的定向改良和新品种选育提供依据。结果表明:(1)K18和K24分别获得11914和6793个差异表达基因;KEGG注释显示,有58个差异基因与花色花香合成相关;进一步分析发现,类黄酮是K18和K24的主要花色素,其合成基因在小花蕾期显著上调,其中K18通过查尔酮异构酶基因(CHI)、类黄酮-3′,5′羟化酶基因(F3′5′H)和黄酮醇合酶基因(FLS)途径生成黄酮醇,K24则通过花青素合成酶基因(ANS)途径生成花青素。(2)qRT-PCR验证表明,萜类骨架基因羟甲基戊二酰辅酶基因(HMGS)、羟基-3-甲基戊二酰辅酶A还原酶基因(HMGR2)和甲羟戊酸-5-焦磷酸合酶基因(MVD)等的表达量均在K18盛花期最高,同时6个下游的萜烯合酶(TPS)基因在K18中表达量比K24上调100倍以上。(3)定量分析表明,K24、K18中的花色素苷总含量分别为608.74、122.28μg·g-1,K18花色苷含量仅为K24的20%;K24花中色素物质主要成分为矢车菊素苷,使其花色呈红色;K18中飞燕草素苷含量相对较高(花色为黄色)。研究推测,ANS基因的较高表达可能是K24花瓣中花色苷含量高于K18的原因之一,K18通过CHI、F3′5′H、FLS途径积累了大量黄酮醇而不是花青素,从而影响了花朵颜色的决定。

In order to explore the molecular mechanism of the formations of Cymbidium hybrid flower color and scent,we got transcriptomic data of Cymbidium hybrid‘Yufeng’(K18,yellow)and‘Fuyundanxia’(K24,purplish red)for different flowering stages by RNA-Seq technique and analyzed the expression levels of genes related to flower color or scent.Present transcriptomic datas provide an important reference for the directional improvement of flower color or scent and creation of special breeding varieties.The results showed that:(1)a total of 11914 and 6793 differentially expressed genes(DEGs)were selected in K18 and K24,respectively;of which 58 DEGs related to flower color and scent formation base on kyoto encyclopedia of genes and genomes(KEGG)annotation.Further analysis indicated that flavonoids are the main flower pigment in K18 and K24 and expression of synthetic genes were up-regulated significantly at bud stage.Among them,flavonols were generated by chalcone flavanone isomerase gene(CHI),flavonoid 3′5′-hydroxylase gene(F3′5′H)and flavonol synthase gene(FLS)in K18;Anthocyanins were got by anthocyanidin synthase gene(ANS)in K24.(2)qRT-PCR analysis showed that the expression levels of hydroxymethylglutaryl-CoA synthase gene(HMGS),hydroxy-3-methylglutaryl coenzyme A reductase gene(HMGR2),mevalonate-5-diphosphatase gene(MVD)and so on in terpenoid skeleton biosynthesis all are the highest at the flowering period in K18.Moreover,the expression levels of six TPSs in K18 were more than 100 times than that in K24.(3)Quantitative analysis showed anthocyanin content in K18(122.28μg·g-1)was about 20%of that in K24(608.74μg·g-1).The main pigment component in K24 was cyanidin,which made the flower color red,while the delphinin level in K18 was relatively high(the yellow flower).Study speculated that the overexpression of ANS may be one of the reasons for higher anthocyanin content in K24 petals than that in K18.Flavonol rather than anthocyanin was accumulated in K18 through CHI,F3′5′H and FLS pathway,which affects the determination of flower color.