| Mulberry tree is a deciduous perennial woody plant, classified as the Rosales Moraceae Morus. Fructus mori, the fruit of Morus alba, is commonly used in Chinese medicines due to a variety of secondary metabolites. Flavonoids represent a large class of secondary plant metabolites, of which anthocyanins are the most conspicuous class, due to the wide range of colors resulting from their synthesis. The existence of such a diverse range of functions and types of anthocyanins raises questions about how these compounds are synthesized and how their synthesis is regulated. In most cases, mutations affecting different steps of the anthocyanin biosynthesis pathway were isolated and characterized well before their function was identified or the corresponding gene was isolated.Mulberry has two fruit color phenotypes,white and balck, yet no research reflects the biochemical background of this phenomenon. In this study, we evaluated 4 mulberry cultivars for total sugar contant through Anthracene ketone colorimetric method. The oucome is that white cultivar ’ZhenZhuba’ contains the highest content as 7.81%, which is twice as much as black cultivars ’JiaLing 30’,’HongGuo 1’ and ’DaShi’ that are separately 3.95%,3.98% and 3.69%.We also detected sugar degree of white and red cultivars by saccharimeter. Result indicated that the mean value of white cultivar is much higher than that of black ones.pH values of different mulberry fruits have been determined by pH meter, which came out that pH of ’ZhenZhubai’ is obviously higher than that of ’JiaLing 30’,’HongGuo 1’ and ’DaShi’. Then we analyzed types and contant of anthcyanins through high performance liquid chromatography. Result demonstrated that there have been two anthocyanins, cyanidin-3-glucoside and cyanidin-3-rutinoside. In the ripened fruits, and cyanidin-3-glucosideconcentration in ripend white cultivar is nearly undetectable (0.1364 mg·g-1 dry weight), counter to 16.9792 mg·g-1 dry weight of black one ’Jialing 30’.Six genes involved in cyanidin biosynthesis encoding chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), favonoid 3′-hydroxylase(F3′H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS) were isolated from the fully red cultivar ’Jialing 30’(Morus atropurpurea Roxb.) through analogous cloning. In addition, CHI and ANS have already amplified CDS sequence and full-length cDNA.The expression of the six genes, especially MaDFR and MaANS in white cultivar was much weaker as compared to those red cultivars through RT-PCR. The result suggest the late genes in the anthocyanin biosynthetic pathway were coordinately expressed during coloration of black mulberry fruit. Low expression of these genes resulted in absence or extremely low anthocyanin accumulation in white cultivars. |
