紫叶甘蓝型油菜花青素合成的转录组-代谢组联合分析

Transcriptomic and Metabolomic Analysis of Anthocyanin Synthesis in Purple Leaf Brassica napus

通过筛选甘蓝型油菜绿叶和紫叶突变体叶片中差异表达基因和差异代谢物,为解析花青素合成机理奠定理论基础。对苗期叶片呈紫色的甘蓝型油菜(PL)和叶片呈绿色的甘蓝型油菜ZS11(GL)幼苗表型观察发现,PL在长出2片真叶(3周)时紫色斑驳分布,随着发育紫色逐渐加深,抽薹期后紫色逐渐变浅最终消失(>16周),GL叶片则全时期呈绿色;转录组KEGG分析在第6,13,16周找到2 523个共差异表达基因,上述差异表达基因在花青素合成途径显著富集。与花青素合成相关的24个基因显著差异表达,包括3个MYBL2、1个C4H、1个F3H、2个F3′H、2个TT8、3个DFR、4个ANS、5个UGT、3个TT19,上述基因在第6,13周PL叶片中表达量均高于GL。选取8个差异表达基因进行qRT-PCR验证,结果与转录组分析数据趋势一致。花青素靶向代谢组共检测到50种花青素,其中29种积累差异显著;PL相对于GL有16种花青素积累上调,13种花青素积累下调。PL叶片中多种矢车菊素积累量显著增加,而矮牵牛素积累量显著下降,花青素合成途径中差异表达基因和差异代谢物的表达量均达到显著水平。TT8及其靶基因(DFR、ANS、UGT、TT19)在发育早期(6~13周)的上调促进了PL中以矢车菊素为主的花青素的积累以及矮牵牛素为主的花青素的减少,导致叶片叶色出现差异。而发育后期(13~16周),这些花青素合成基因的下调和花青素的降解可能导致花青素积累的减少,使PL由紫叶转变为绿叶。

By screening differentially expressed genes and metabolites in the green and purple leaves of Brassica napus,it lays a theoretical foundation for the analysis of mechanism of anthocyanin synthesis.Phenotypic observation of GL and PL seedlings showed that PL exhibited a mottled distribution of purple when two true leaves were grown(3 weeks),as the purple gradually deepened during development,it gradually became lighter and eventually disappeared after the bolting stage(>16 weeks),while GL leaves remained green throughout the entire period;transcriptome analysis identified 2523 co-differentially expressed genes at weeks 6,13,and 16,and these differentially expressed genes were significantly enriched in the anthocyanin synthesis pathway.Twenty-four genes related to anthocyanin synthesis were significantly differentially expressed,including 3 MYBL2,1 C4H,1 F3H,2 F3′H,2 TT8,3 DFR,4 ANS,5 UGT,and 3 TT19.The expression levels of these genes in PL leaves were higher than those in GL at 6 and 13 weeks.Eight differentially expressed genes were selected for qRT-PCR validation and the results were consistent with the trend of transcriptome analysis data.A total of 50 anthocyanins were detected in the anthocyanin-targeted metabolome,of which 29 showed significant difference in accumulation;compared to GL,PL had 16 types of anthocyanin accumulation upregulated and 13 types of anthocyanin accumulation downregulated.The up-regulation of TT8 and its target genes(DFR,ANS,UGT,TT19)in early development(6-13 weeks)promoted the accumulation of cyanidin-based anthocyanins and the decrease of petunian-based anthocyanins in PL.The expression levels of differentially expressed genes and metabolites in the anthocyanin synthesis pathway reached significant levels.