Genome-wide identification and comparative analysis of GST gene family in apple (Malus domestica) 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 (GST) genes are involved in anthocyanin transportation. Here, a total of 52, 42, 50, and 29GSTgenes 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 appleGSTgenes were further analyzed. TheGSTgene family expansion in apple likely occurred through tandem duplications, and purifying selection played a pivotal role in the evolution ofGSTgenes. Synteny analysis showed strong microsynteny between apple andArabidopsis/strawberry, but no microsynteny was detected between apple/strawberry/Arabidopsisand 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 ofGSTgenes in apples.MdGSTF12was strongly induced by ALA, suggesting thatMdGSTF12may play a role in ALA-induced anthocyanin accumulation. These results provide a detailed overview ofGSTgenes in fourRosaceaespecies and indicate thatGSTsare involved in ALA-induced anthocyanin accumulation.