巴西蕉果肉类黄酮生物合成特点及其关键酶基因的差异表达分析

Characteristics of Flavonoids Biosynthesis and the Differential Expression Analysis of the Key Enzyme Genes in Musa AAA Group cv Brazilian Fruit Pulp

为了明确巴西蕉果肉类黄酮生物合成的特点及其关键酶基因的差异表达特性,本研究选取抽蕾期(0 DAF)、断蕾期(20 DAF)、采收期(80 DAF)、成熟度Ⅱ期(8 DPH)、成熟度Ⅵ期(16 DPH)的巴西蕉的果肉,分别测量总黄酮的含量,观察其变化趋势。分别提取根、叶、花、果实以及上述五个时期的果肉RNA进行转录组测序,分析类黄酮生物合成关键酶基因在不同组织器官及不同发育成熟阶段的表达特性,并对其中10个关键酶基因的表达进行验证。结果表明从抽蕾期至断蕾期再到采收期,巴西蕉果肉黄酮含量呈明显的下降趋势,至采收时下降到最低点,在采后成熟过程中小幅上升再下降。类黄酮生物合成6个关键酶基因家族共78个基因在巴西蕉不同组织器官中是差异表达的,其中3个基因在根、叶、花和果实中都高水平表达,有42个、11个、18个、8个基因分别在根、叶、花、果实中高表达;这78个基因也在巴西蕉果实不同发育成熟阶段差异表达,有4个基因在果实发育成熟阶段都高水平表达,有27个、27个、19个、15个、9个基因分别只在抽蕾期、断蕾期、采收期、成熟度Ⅱ期和成熟度Ⅵ期中高水平表达;类黄酮生物合成关键酶基因CHS(Ma02_t24860.1)、CHI(Ma11_t21950.1)和F3'H(Ma03_t31570.1和Ma05_t26350.1)与总黄酮的变化趋势相似,推测这4个关键酶基因在香蕉果实黄酮生物合成过程中具有非常重要的作用。研究结果可为解析巴西蕉类黄酮生物合成的分子机制提供帮助。

In order to understand the characteristics of flavonoid biosynthesis in banana fruit and the differential expression characteristics of the key enzyme genes in the fruit of the ＇Baxijiao＇, ＇Baxijiao＇ pulp was selected in fower emerging （0 DAF）, flower cutting （20 DAF）, fruit harvest （80 DAF）, maturity II （8 DPH）, and maturityVI （16 DPH）, and the total flavonoids were measured to observe the trend. The RNAs of the above five periods and roots, leaves, flowers and fruits were extracted. The expression characteristics of key genes of flavonoid biosynthesis in the different ripening stages and different organs were analyzed, and the expression of 10 key enzyme genes wasverified. The results showed that the content of flavonoids in ＇Baxijiao＇ pulp displayed a gradually decreased trend from flower emerging to flower cutting and reached to the lowest point when it was on fruit harvest, and then with a slightly increase and finally decreased during maturity I1. A total of 78 genes of six key enzyme gene families in flavonoid biosynthesis were differentially expressed in different tissues and organs. Three genes are highly expressed in the whole process. There were 42, 11, 18 and 8 genes were highly expressed at roots, leaves, flowers, fruits, respectively. A total of 78 genes of six key enzyme gene families in flavonoid biosynthesis were differentially expressed in different stages of fruit development and ripening stages. Four genes are highly expressed in the whole process. There were 27, 27, 19, 15 and 9 genes were highly expressed at flower emerging, flower cutting, fruit harvest, maturity 11, maturityVI, respectively. The key genes of flavonoids biosynthesis CHS （Ma02_t24860.1）, CHI （Ma11_t21950.1） and F3＇H （Ma03_t31570.1 and Ma05_t26350.1） were similar to those of the total flavonoids. It is speculated that these four key enzyme genes play a very important role in the biosynthesis of banana fruit flavonoids. The results might lay a foundation for understanding the molecular mechanism of ＇Ba- xijiao＇ flavonoid biosynthesis.