Molecular Mechanism Of SmTT8 Mediating Light-dependent Anthocyanin Biosynthesis In Eggplant Fruits

Eggplant(Solanum melongena L.)is an important vegetable crop in China,with abundant germplasm resources,and fruit color is an important economic trait index.Anthocyanins are the main pigments of light-dependent purple eggplant fruits,and their synthesis is mainly regulated by the external environment and their genetic mechanisms.In this paper,the light-dependent purple eggplant "sanyueqie" was used as the experimental material to isolate and identify the key transcription factor Sm TT8 involved in the transcription and regulation of anthocyanin metabolism in eggplant.The main findings are as follows:1.Using the eggplant genome database,the b HLH transcription factor Sm TT8 involved in eggplant anthocyanin biosynthesis was identified through evolutionary analysis and multiple sequence alignment analysis.Under light conditions,its expression in different tissues of eggplant and anthocyanin synthesis structural gene expression positive correlation.2.Using RNAi and Agrobacterium-mediated genetic transformation technology to obtain Sm TT8 gene-specific silent strains.It was found in the Sm TT8 silenced lines that the inhibition of Sm TT8 expression resulted in the inhibition of anthocyanins accumulation in the tissues of transgenic eggplant.3.Through RNA-seq analysis of wild-type and transgenic plant eggplant peels,a total of 2607 differential genes were identified,of which 1316 genes were up-regulated,mainly involved in photosynthesis and chlorophyll metabolism,and down-regulated There are 1291 genes,which are mainly involved in phenylpropane biosynthesis and flavonoid biosynthesis.In addition,down-regulation of Sm TT8 in transgenic plants resulted in significant down-regulation of anthocyanin synthesis structural genes,Sm HQT and Sm FLS in the phenylpropane pathway were significantly up-regulated,and Sm CCo AOMT,a key lignin synthesis gene,was significantly down-regulated.4.Using UHPLC-Q-Orbitrap-MS to analyze differentially expressed metabolites,it was found that the 14 differentially up-regulated metabolites were mainly amino acids and amino acid derivatives,and the 19 differentially down-regulated metabolites were mainly flavonoids.Combining transcriptome results and phenotypic difference analysis,the chlorophyll content detected in the transgenic eggplant peel was significantly higher than that of the wild type,while the lignin content was significantly reduced.5.Transient overexpression of Sm TT8 and Sm MYB1 can induce anthocyanin accumulation in tobacco leaves.Overexpression of Sm MYB1 can also induce anthocyanin accumulation,but the content is significantly lower than the effect of co-injection.Promoter induction experiments showed that Sm TT8 and Sm MYB1 can synergistically activate Sm DFR and Sm ANS promoters.In summary,this study identified a b HLH transcription factor Sm TT8 involved in light-dependent purple anthocyanin biosynthesis,which can synergize with the anthocyanin synthesis regulator Sm MYB1 to enhance the transcriptional activity of the anthocyanin synthesis structural promoter Further promote the synthesis of anthocyanins.