Identification of MATE gene family and its association with flavonoid accumulation in pepper （Capsicum annuum L.）

【Objective】 Multidrug and toxic extrusion compound transporter family members （CaMATE） were identified from the whole genome of pepper，and their expression patterns in different pepper tissues and their association with flavonoid accumulation were analyzed，which provided theoretical basis for the subsequent research on the biological function of CaMATE gene family in pepper flavonoid transport and the breeding and improvement of new pepper varieties with high flavonoid content.【Method】 Peel of four pepper varieties with different genotypes（HJ10-1， HJ11-3-1， CJ12-17-1， and 0622-1-3-2-1-3-1） were used as the research materials for this study. CaMATE gene family members were identified by bioinformatics methods， and the basic physicochemical properties， gene structure， phylogenetic relationship of the family members were systematically analyzed. The CaMATE genes regulating the accumulation of flavonoids in pe-pper were screened by the expression patterns in different tissues of four pepper varieties with different genotypes， and the expression of eight CaMATE family genes were detected by real-time fluorescence quantitative PCR. Furthermore， the correlation analysis on CaMATE family genes with highly expressed transcription factors in flavonoid components in four pepper varieties was performed.【Result】 A total of 61 CaMATE gene family members were identified from the pepper genome，named CaMATE1-CaMATE61， which were unevenly distributed on chromosome 13. Their encoded proteins contained 2-12 transmembrane structures and 3 types of MATE conserved domains， which were mainly located in the cell membrane. The cis-acting elements in the promoter region of CaMATE family genes were mainly involved in hormone response， growth and development， and defense or stress response. Phylogenetic analysis showed that the MATE members were divided into six subfamilies （I-VI）， and the similarity of MATE members between pepper and tomato was high. The expression patterns of CaMATE family members in different tissues were quite different， among which CaMATE3， CaMATE6 and CaMATE23 were highly expressed in four pepper varieties. The relative expression level of CaMATE25 gene was only high in the peel of CJ12-17-1 pepper at 30 d after flowering. The results of real-time fluorescence quantitative PCR were consistent with those of transcriptome sequencing. Correlation analysis showed that CaMATE3， CaMATE25， CaMATE38 and CaMATE51 genes were strongly correlated with more than 15 flavonoid components， and these four genes were also strongly correlated with the highly expressed transcription factors， bHLH96， and HD-ZIP3.【Conclusion】 The 61 members of CaMATE gene family are identified from the pepper genome. The highly expressed genes （Such as CaMATE3 and CaMATE25） in pepper fruits have strong correlation with multiple flavonoid components， suggesting that they are involved in regulating the transport process of pepper flavonoids. Moreover， MYB113， bHLH96， and HD-ZIP3 are screened to be upstream regulators of potential flavonoid transport CaMATE family genes.