| Interest in polyphenols is increasing among scientists, because of its biological activity and function. A variety of polyphenol is beneficial to human health, on the one hand, it acts as an active substance to stimulate the human immune activity, on the other hand, it should suppress the proliferation of cancer cells. So polyphenols can effectively prevent human from many kinds of chronic diseases and cancer, and improve the ability in radical scavenging. For plants, polyphenols have the function to protect them from a variety of biotic and abiotic stress, such as, pests, pathogenic microorganism, drought, UV radiation, etc. MYB family transcription factors are widely present in eukaryotes, and the largest proportion is in the plant kingdom. As transcription factor, some members of the MYB family can regulate the synthesis of secondary metabolites in plants by regulating the expression of target genes. In our study, we analysis the function of Arabidopsis transcription factor AtMYB11 and AtMYBl2 in some Solanaceae crops, respectively. The main results are as follows:1 AtMYB11 regulates caffeoylquinic acid and flavonol synthesis in tomato and tobaccoWe transferred the Arabidopsis transcription factor AtMYB11 into tomato fruit, during the ripening stage, the fruit of AtMYB11-expressing tomato was orange, instead of red which was the normal color in wild-type fruits. Analysis the polyphenol content in transgenic and wild-type tomato by HPLC, the results showed that wild-type only contained limited content of polyphenols, compared to the increased level in transgenic tomato fruits. The polyphenols contents enrichment was related to the induced gene expression in polyphenols synthesis pathway.AtMYB11-expressing tomato fruit showed 3-fold increased in antioxidant capacity.We expressed AtMYB11 in tobacco by constitutive promoter CaMV35S, among the three lines of transgenic tobacco in T1 generation, the major flavonols contained in tobacco, the highest content of rutin increased to 15.7-fold, the kaempferol rutinoside increased 6.2-fold at most; the major phenolic acid, chlorogenic acid increased to 6.2-fold mostly. The high content enrichment of polyphenols in AtMYB11-expressing tobacco leaves was caused by the induced expression level of multiple genes involved in the polyphenols synthesis pathway.2 Evaluation of plant resistance to phytopathogens for AtMYb12 transgenic tobacco.Inoculated the AtMYB12-expressing tobacco (polyphenol content increased) with tobacco bacterial disease, Ralstonia solanacearum strains. The symptoms extended to whole leaf in wild-type, and the symptoms were only found in the half of inoculated leaf. The growth rate of bacteria in the transgenic tobacco leaves was significantly lower than that in wild-type. Infection 96 h later, the bacterial number in wild-type leaves was 3.27-fold more than the number in transgenic tobacco leaves. The result of NBT staining showed that, rapid accumulation of superoxide happened in AtMYB12-expressing tobacco leaves after the inoculation.We inoculated tobacco leaves with two tobacco fungal diseases:Allernaria alternata and Colletotrichum micotianae Averna in vitro.AtMYB12-expressing tobacco showed a significant resistance phenotype:the shorter lesion diameter in inoculated leave; less conidium numbers; After inoculation no significant increase in the number of spores in AtMYB12-expressing tobacco leaves; HR response occurred after the fungi infection in the AtMYB12-expressing tobacco leaves, and the wild-type did not appear.3 Gene expression profiling in AtMYB12-expressing tomatoAiming at the high content of polyphenols in AtMYB12-expressing tomato, we use gene expression profiling to analysis the difference between wild-type and transgenic tomato fruits. Among the total number of 21170 genes, the number of genes, which were up-regulated to 2-fold higher, were 1906,2-fold higher down-regulated genes were 2077. In various biological function categories, differential gene performance mostly in metabolic process, catalytic activity and binding function. Based on the results of gene expression profiling and the reported caffeoylquinic acid synthesis pathway, we over-expressed gene NtHCT and NtC3H in wild-type tobacco Samsun, respectively, to identify their gene function, and analysis their effect on tobacco polyphenols synthesis.4 Development of marker-free transgenic potato tubers enriched in caffeoylquinic acids and flavonols.Potato is a major crop worldwide that meets human economic and nutritional requirements. Potato has several advantages over other crops:easy to cultivate and store, cheap to consume, and rich in a variety of secondary metabolites. In this study, we generated three marker-free transgenic potato lines that expressed the Arabidopsis thaliana flavonol-specific transcriptional activator AtMYB12 driven by the tuber-specific promoter Patatin. Marker-free potato tubers displayed increased amounts of caffeoyl quinic acids (CQAs) (3.35-fold increases on average) and flavonols (4.50-fold increase on average). Concentrations of these metabolites were associated with the enhanced expression of genes in the CQA and flavonol biosynthesis pathways. Accumulation of CQAs and flavonols resulted in two-fold higher antioxidant capacity compared to wild-type potatoes. Tubers from these marker-free transgenic potatoes have therefore improved antioxidant properties. |
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