甜菊糖苷积累与其生物合成基因表达的关系

The Relationship between Steviol Glycosides Accumulation and Biosynthesis Genes Expression

为探究甜叶菊叶片中甜菊糖苷积累与其合成途径上关键基因表达的关系,本研究分别检测了鑫丰3号苗期不同冠层和3个不同品种甜叶菊(守田3号、江甜3号、谱星1号)收获期混合叶片样品中多种糖苷的含量,同时定量检测对应样品中甜菊糖苷合成关键基因的表达水平。结果显示,总糖苷在鑫丰3号顶叶中最高,底叶中最低,而多数检测基因(6/8)表达水平也在顶叶最高底叶中最低;单一糖苷甜菊苷在顶叶中积累最高,而其催化酶编码基因Sr UGT74G1表达也在顶叶中最高;莱鲍迪苷A则在底叶中积累最多,其催化酶编码基因Sr UGT76G1表达水平也在底叶中表达最高。3个品种相比,总糖苷和莱鲍迪苷A的积累在江甜3号中最高,谱星1号中最低;甜菊苷的积累在守田3号中最高,江甜3号中最低,但基因表达水平与糖苷积累趋势一致的类似结果并未在不同品种间出现。由此可知,甜菊糖苷合成基因的表达水平可以影响总糖苷的积累,且在同一甜叶菊品种中单一糖苷合成调控基因的表达水平可以反映其调控的单糖苷的积累量。

In order to explore the relationship between the accumulation of steviol glycosides（ SGs） and expression of SGs biosynthesis pathway genes,SGs content and composition in stevia leaves of different canopies of one variety（ Xinfeng 3） and three varieties（ Shoutian 3,Jiangtian3,Puxing 1） were analyzed and the related genes expression were tested by real-time PCR. The results showed that the accumulation of total SGs was highest in the top leaves and lowest in the bottom leaves of Xinfeng 3. Among the eight tested genes,six of them had the highest expression in the top leaves and had the lowest in the bottom leaves. The stevioside accumulation was highest in top leaves and the expression of its catalytic enzyme encoding gene Sr UGT74G1 was also highest in top leaves. And rebaudioside A（ RA） content was the highest in bottom leaves and the expression of its catalytic enzyme encoding gene Sr UGT76G1 was highest in the bottom leaves. Among three varieties,the accumulation of total SGs and rebaudioside A（ RA） was highest in Jiangtian 3 and lowest in Puxing 1,while the stevioside accumulation was highest in Shoutian 3 and lowest in Jiangtian 3. However expression of related genes did not show the same trend to SGs accumulation in three stevia varieties. So it was deduced that expression level of SGs biosynthesis pathway genes affected the SGs accumulation significantly,and in the same variety,the expression level of catalytic enzyme encoding gene could reflect the accumulation of corresponding steviol glycoside.