Functional characterization of MATE gene family under abiotic stresses and melatonin-mediated tolerance in dragon fruit (Selenicereus undatus L.)

Multidrug and toxic compound extrusion (MATE) are transporter proteins exist widely in all living organisms which are involved in toxins detoxification. In plants, MATE proteins function in detoxification of endogenous secondary metabolites, exogenous agents, and other plant developmental processes. In this study, the identifi-cation and expression analysis of MATE gene family was conducted to analyse their response against heavy metal and salt stresses in pitaya seedlings. We have identified and analysed 35 MATE gene family members from pitaya genome which were mapped on all 11 chromosomes. All members of this family were named from HuMATE-1 to HuMATE-35, divided into 14 groups based on phylogenetic analysis, tree topology and motif's structure. The subcellular localization of 35 proteins was predicted and data showed that 62 % of the total gene members were localized on plasma membrane. The syntenic analysis showed 14 collinearity gene pairs in which two gene pairs showed tandem duplication and twelve pairs showed segmental duplication on the chromosomes. Genes motif composition and exon-intron structures were found more similar within the same group. Cis-acting element in promoter regions predicted their regulatory function in plant toxin detoxification and defence processes. RNA-Seq analysis of HuMATE candidate genes exhibit higher expression under copper and salt stresses individually as well as both in combination. Melatonin applications regulate HuMATE gene expression effectively for both copper and salt stresses, thus enhancing pitaya seedling growth and development. Moreover, RT-qPCR analysis of highly expressed 10 HuMATE genes at different developmental stages of pitaya validates the expression and RNA-Seq results. Our finding predicts thatHuMATE-7/11/12/28 genes are putative candidates and might play a key role in plant toxin detoxification produced by heavy metals accumulation and high soil salinity. Furthermore, our results provide the foundation for development of stress-tolerant genotypes under various climate scenarios through forward and reverse genetic breeding programs.