彩叶桂(Osmanthus fragrans)品种‘虔南桂妃’叶片红色消退过程中的转录组分析

Analysis of Transcriptome During the Red-leaf Faded Process of A Osmanthus fragrans Cultivar′Qiannan Guifei′

彩叶桂(Qsmanthus fragrans)叶片发育不同时期色泽变化具有显著差异,但目前对于其内在的分子调控机制尚不清楚。本研究利用彩叶桂品种‘虔南桂妃’红色(R)、黄绿色(YG)和绿色(G)叶片进行高通量测序,以期在转录组水平上解析叶色变化的潜在原因。通过系统分析转录组数据,共得到36.66 Gb的碱基数据,检测出32252个新转录本。在R-vs-G、R-vs-YG和YG-vs-G比较组中共筛选到23954个差异表达基因(differentially expressed genes,DEGs),其中包含57类共3308个转录因子家族成员,且下调表达的差异基因数目大于上调表达的基因数目。KEGG和GO功能分析表明,差异表达基因主要与“催化活性”、“细胞”和“代谢”等生物学功能相关。此外,筛选到了6个类黄酮生物合成途径上显著差异表达的基因,分别编码查尔酮合成酶(CHS)、查尔酮异构酶(CHI)、二氢黄酮醇4-还原酶(DFR)、UDP-糖基转移酶(UGT)、黄酮醇合成酶(FLS)和花青素合成酶(ANS)。与红色叶片相比,这些基因的表达量在黄绿色和绿色叶片中显著降低。推测下调表达的6个类黄酮生物合成途径基因可能促进了‘虔南桂妃’叶片红色的消退。本研究结果对深入理解彩叶桂叶色变异的分子机制具有重要的理论价值,获得的基因序列为今后桂花叶色遗传改良提供了宝贵的基因资源。

There are significant differences in the leaf coloration of Osmanthus fragrans during different development stages.However,the innate molecular mechanism is unclear at present.In this study,to explore the causes of leaf coloration on transcriptome level,the red(R),yellow-green(YG)and green(G)leaves of a Osmanthus fragrans colour group cultivar′Qiannan Guifei′was used for high-throughput sequencing.By systematically analyzing the transcriptome data,a total of 36.66 Gb bases were obtained,of which 32252 were novel transcripts.23954 genes were defined as differentially expressed genes(DEGs)in groups R-vs-G,Rvs-YG and YG-vs-G,including 3308 transcription factor belonged to 57 classes,the number of down-regulated DEGs was greater than that of up-regulated genes.KEGG and GO analysis showed that the annotated DEGs were mainly related to"catalysis","cell"and"metabolism".In addition,6 DEGs involved in flavonoid biosynthesis were identified,these genes encode chalcone synthase(CHS),chalcone isomerase(CHI),dihydroflavonol 4-reductase(DFR),UDP-glycosyltransferase(UGT),flavonol synthase(FLS)and anthocyanidin synthase(ANS).The expression levels of these genes showed a significant decrease at yellow-green and green leaves compared to that of red leaves,suggesting that red color disappear in the leaves of′Qiannan Guifei′was probably caused by the decrease expressions of 6 flavonoid biosynthetic pathway genes.Overall,our results will be helpful in the investigation of the molecular mechanisms of leaf color variation in Osmanthus fragrans colour group and offer potential genes for the genetic improvement of leaf color in future.