Genome-Wide Identification and Expansion Patterns of SULTR Gene Family in Gramineae Crops and Their Expression Profiles under Abiotic Stress in Oryza sativa

Abstract

Sulfate transporters (SULTRs), also known as H⁺/SO₄^2- symporters, play a key role in sulfate transport, plant growth and stress responses. However, the evolutionary relationships and functional differentiation of SULTRs in Gramineae crops are rarely reported. Here, 111 SULTRs were retrieved from the genomes of 10 Gramineae species, including <i>Brachypodium disachyon</i>, <i>Hordeum vulgare</i>, <i>Setaria italica</i>, <i>Sorghum bicolor</i>, <i>Zea mays</i>, <i>Oryza barthii</i>, <i>Oryza rufipogon</i>, <i>Oryza glabbermia</i> and <i>Oryza sativa</i> (<i>Oryza sativa</i> ssp. indica and <i>Oryza sativa</i> ssp. japonica). The SULTRs were clustered into five clades based on a phylogenetic analysis. Syntheny analysis indicates that whole-genome duplication/segmental duplication and tandem duplication events were essential in the SULTRs family expansion. We further found that different clades and orthologous groups of SULTRs were under a strong purifying selective force. Expression analysis showed that rice SULTRs with high-affinity transporters are associated with the functions of sulfate uptake and transport during rice seedling development. Furthermore, using <i>Oryza sativa</i> ssp. indica as a model species, we found that <i>OsiSULTR10</i> was significantly upregulated under salt stress, while <i>OsiSULTR3</i> and <i>OsiSULTR12</i> showed remarkable upregulation under high temperature, low-selenium and drought stresses. <i>OsiSULTR3</i> and <i>OsiSULTR9</i> were upregulated under both low-selenium and high-selenium stresses. This study illustrates the expression and evolutionary patterns of the SULTRs family in Gramineae species, which will facilitate further studies of SULTR in other Gramineae species.