Genome-Wide Identification and Expression Analysis of GST Genes during Light-Induced Anthocyanin Biosynthesis in Mango (Mangifera indica L.)

Abstract

Anthocyanins are important secondary metabolites contributing to the red coloration of fruits, the biosynthesis of which is significantly affected by light. Glutathione S-transferases (GSTs) play critical roles in the transport of anthocyanins from the cytosol to the vacuole. Despite their importance, GST genes in mango have not been extensively characterized. In this study, 62 mango GST genes were identified and further divided into six subfamilies. MiGSTs displayed high similarity in their exon/intron structure and motif and domain composition within the same subfamilies. The mango genome harbored eleven pairs of segmental gene duplications and ten sets of tandemly duplicated genes. Orthologous analysis identified twenty-nine, seven, thirty-four, and nineteen pairs of orthologous genes among mango MiGST genes and their counterparts in Arabidopsis, rice, citrus, and bayberry, respectively. Tissue-specific expression profiling highlighted tissue-specific expression patterns for MiGST genes. RNA-seq and qPCR analyses revealed elevated expression levels of seven MiGSTs including MiDHAR1, MiGSTU7, MiGSTU13, MiGSTU21, MiGSTF3, MiGSTF8, and MiGSTF9 during light-induced anthocyanin accumulation in mango. This study establishes a comprehensive genetic framework of MiGSTs in mango fruit and their potential roles in regulating anthocyanin accumulation, which is helpful in developing GST-derived molecular markers and speeding up the process of breeding new red-colored mango cultivars.

Keywords: GST; anthocyanin; gene expression; light; mango.

Figure 1

Phylogenetic tree of the characterized MiGST proteins. AtGST proteins were selected as references for representative indicators of each defined subfamily. The Mangifera indica (Mi) proteins are marked with red stars, and Arabidopsis thaliana (At) proteins are indicated by black triangles, with different subfamilies marked by different colors.

Figure 2

Phylogenetic relationships, conserved motif and domain patterns, and gene structures of mango GSTs. (a) Phylogenetic tree constructed based on the complete protein sequences of mango GSTs, with different colors corresponding to different subfamilies. (b) Display of motifs found in MiGSTs proteins. (c) Display of conserved domains found in MiGST proteins. (d) Gene structure of MiGSTs.

Figure 3

The homology relationships among GST genes. (a) The mango MiGST gene family’s synteny is illustrated, with red lines marking the segmental duplications of MiGSTs (highlighted with red color); blue lines indicate the tandem duplications of MiGSTs. (b) The synteny analysis of GST genes across Mangifera indica, Oryza sativa, Arabidopsis thaliana, Citrus sinensis, and Myrica rubra is displayed, highlighting GST gene homologs with purple lines.

Figure 4

Hierarchical clustering of expression profiles for 62 mango GSTs in different tissues. The genes are categorized into Groups A–C. The color bar indicates the expression value from low (blue) to high (red).

Figure 5

Transcriptional profiling of MiGST genes in the peel of ‘Ruby’ (a) and ‘Sensation’ (b) mangoes under bagging treatment and control conditions for 50, 80, and 120 days after full bloom using RNA-Seq data.

Figure 6

Anthocyanin content in ‘Guifei’ mango peel under UV-B/white light (a) and blue light (b) treatments. MiGSTs expression in ‘Guifei’ mango peel analyzed by RNA-seq under UV-B/white light (c) and blue light (d) treatments. The data represent the mean ± standard deviation with n = 3. * represents significant difference (p-value < 0.05); ** represents highly significant difference (p-value < 0.01), as determined by Student’s t-test.

Figure 7

Analysis of MiGST genes in ‘Guifei’ mango peel under UV-B/white light (a) and blue light (b) treatments analyzed by qPCR. Data are depicted as mean values ± standard deviation, derived from three biological replicates (n = 3). * indicates a statistically significant difference at p < 0.05; ** represents a highly significant difference at p < 0.01 between the light-treated and control samples, tested by Student’s t-test.