Anthocyanins are major pigments in the peels of red-series wax apple fruits, and two principal components of them, namely, the cyanin and the peonidin, are non-methoxylated and methoxylated anthocyanins, respectively. Anthocyanin O-methyltransferases (AOMTs) are an important group of enzymes that have the ability to catalyze anthocyanins methylation to promote the solubility, stability, and bioactivity of anthocyanins. Although AOMT genes have been studied in a variety of plants, the function of them in wax apple is generally not well understood.
The anthocyanin composition in peels of two wax apple cultivars was determined by High Performance Liquid Chromatography Tandem Mass Spectrometry (HPLS-MS). The genome-wide analysis of the AOMT genes was performed with bioinformatics technology, and the expression patterns of different plant tissues, cultivars, fruit ripening stages, and exogenous abscisic acid (ABA) treatments were analyzed by transcriptome sequencing analysis and real-time quantitative PCR verification. An initial functional evaluation was carried out
Only two main compositions of anthocyanin were found in peels of two wax apple cultivars, and it was worth noting that Tub Ting Jiang cultivar contained non-methoxylated anthocyanin (Cy3G) only, whereas Daye cultivar contained both non-methoxylated and methoxylated (Pn3G) anthocyanins. A total of six SsAOMT genes were identified in the whole genome of wax apple, randomly distributing on three chromosomes. A phylogenic analysis of the protein sequences divided the SsAOMT gene family into three subgroups, and all SsAOMTs had highly conserved domains of AOMT family. In total, four types of stress- related and five types of hormone- related cis-elements were discovered in the promoter region of the
In conclusion, SsAOMT5 was responsible for methylated anthocyanin accumulation in the peels of wax apple and played an important role in red coloration in wax apple peels.