Genome-wide identification and comparative analysis of GST gene family in apple () and their expressions under ALA treatment.

Anthocyanins, a subclass of flavonoids, are synthesized at the cytoplasmic surface of the endoplasmic reticulum (ER), which then accumulate in vacuoles. Plant glutathione S-transferase () genes are involved in anthocyanin transportation. Here, a total of 52, 42, 50, and 29 genes were identified from apple, pear, peach, and strawberry, respectively, through a comprehensive genome-wide survey. Based on phylogenetic analyses, the GST proteins of the four crops could be divided into the classes Phi, Tau, DHAR, TCHQD, and Lambda. The structure and chromosomal distribution of apple genes were further analyzed. The gene family expansion in apple likely occurred through tandem duplications, and purifying selection played a pivotal role in the evolution of genes. Synteny analysis showed strong microsynteny between apple and /strawberry, but no microsynteny was detected between apple/strawberry/ and rice. Aminolevulinic acid (ALA), a key precursor of tetrapyrrole compounds, can significantly improve anthocyanin accumulation in fruits, Using RNA-seq and qRT-PCR analysis, we found that ALA treatment led to the differential expression of genes in apples. was strongly induced by ALA, suggesting that may play a role in ALA-induced anthocyanin accumulation. These results provide a detailed overview of genes in four species and indicate that are involved in ALA-induced anthocyanin accumulation.