Characterization, genetic diversity, phylogenetic relationships, and expression of the aluminum tolerance MATE1 gene in Secale species

Aluminum (Al) is the main limiting factor for crop production in acidic soils. Efflux of organic acids is one of the mechanisms that determine Al-tolerance, and an Al-activated citrate transporter (multidrug and toxic compound extrusion) MATE1 gene is involved in different species. The contribution of the rye MATE1 gene (ScMATE1) depends on the rye (Secale cereale L.) cultivars and the crosses analyzed; there is no information about different rye species. The cDNA sequences, phylogenetic relationships, Al-tolerance, citrate exudation, and expression of the ScMATE1 gene were analyzed in several cultivars and wild species/subspecies of the Secale genus. Genotypes highly tolerant to Al were found within this genus. For the first time, sequences of the cDNA of the ScMATE1 gene were isolated and characterized in wild ryes. At least two copies of this gene were found likely to be related to Al-tolerance. The sequence comparison of 13 exons of ScMATE1 revealed variability between species, but also inter- and intra-cultivars. Variations were found in the Al-induced expression of ScMATE1 gene, as well as its contribution to Al-tolerance. The pattern of citrate exudation was inducible in most of the species/subspecies studied and constitutive in few. The phylogenetic analysis indicated that ScMATE1 is orthologue of two genes (HvMATE1 and TaMATE1) involved in the Al stress response in barley and wheat, respectively, but not orthologue of SbMATE, implicated in Al-tolerance in sorghum. ScMATE1 is involved in the response to Al stress in ryes, but its contribution to Al-tolerance is complex, and like in other species, there are tolerant and sensitive alleles in the different cultivars and species studied.