Genome-Wide Identification of the Sulfate Transporters Gene Family in Blueberry (Vaccinium spp.) and Its Response to Ericoid Mycorrhizal Fungi

Sulfur metabolism plays a major role in plant growth and development, environmental adaptation, and material synthesis, and the sulfate transporters are the beginning of sulfur metabolism. We identified 37 potential VcSULTR genes in the blueberry genome, encoding peptides with 534 to 766 amino acids. The genes were grouped into four subfamilies in an evolutionary analysis. The 37 putative VcSULTR proteins ranged in size from 60.03 to 83.87 kDa. These proteins were predicted to be hydrophobic and mostly localize to the plasma membrane. The VcSULTR genes were distributed on 30 chromosomes; VcSULTR3;5b and VcSULTR3;5c were the only tandemly repeated genes. The VcSULTR promoters contained cis-acting elements related to the fungal symbiosis and stress responses. The transcript levels of the VcSULTRs differed among blueberry organs and changed in response to ericoid mycorrhizal fungi and sulfate treatments. A subcellular localization analysis showed that VcSULTR2;1c localized to, and functioned in, the plasma membrane and chloroplast. The virus-induced gene knock-down of VcSULTR2;1c resulted in a significantly decreased endogenous sulfate content, and an up-regulation of genes encoding key enzymes in sulfur metabolism (VcATPS2 and VcSiR1). These findings enhance our understanding of mycorrhizal-fungi-mediated sulfate transport in blueberry, and lay the foundation for further research on blueberry–mycorrhizal symbiosis.