Re-sequencing and Transcriptomic Analysis Reveal Differential Expression Patterns and Sequence Variation in Glucosyltransferase Gene Related to Anthocyanin Biosynthesis in Walnut ( Juglans Regia L.)

The color of walnut peel, usually green during the development stages, is one of the important appearance qualities of walnut fruit. Red walnut 'RW-1' with red peel is a specific germplasm resources due to anthocyanin accumulation, but the mechanism remains unclear. Here, re-sequencing and transcriptome were used to analyze the differences of anthocyanin accumulation in walnut peel with different colors. There were 2,696,620 SNPs and 495,238 InDels between 'Zhonglin 1' and 'RW-1', and the genetic relationship between them was closer than that of either and walnut reference genome 'Chandler'. 1,156 differentially expressed genes (DEGs) with structural polymorphisms were screened by combining re-sequencing and transcriptome analysis. LOC108991235 (JrUFGT5), encoding anthocyanidin 3-O-glucosyltransferase, was identified by KEGG function enrichment. The JrUFGT5 gene base substitutions identified in the coding sequence (CDS) region resulted in amino acid variation, but did not occur in the protein domain region. The expression pattern of JrUFGT5 gene was positively correlated with the anthocyanin accumulation in different walnut peels, and the subcellular localization analysis showed JrUFGT5 was located in the cytoplasm and nucleus. Collectively, these findings revealed the differential expression patterns and sequence variation of a crucial anthocyanidin 3-O-glucosyltransferase gene in walnuts with different colors, which is of great significance to the exploration of the mechanism of anthocyanin biosynthesis in red walnut.