Comprehensive identification and expression analyses of sugar transporter genes reveal the role of GmSTP22 in salt stress resistance in soybean

Abstract

The transport, compartmentation and allocation of sugar are critical for plant growth and development, as well as for stress resistance, but sugar transporter genes have not been comprehensively characterized in soybean. Here, we performed a genome-wide identification and expression analyses of sugar transporter genes in soybean in order to reveal their putative functions. A total of 122 genes encoding sucrose transporters (SUTs) and monosaccharide transporters (MSTs) were identified in soybean. They were classified into 8 subfamilies according to their phylogenetic relationships and their conserved motifs. Comparative genomics analysis indicated that whole genome duplication/segmental duplication and tandem duplication contributed to the expansion of sugar transporter genes in soybean. Expression analysis by retrieving transcriptome datasets suggested that most of these sugar transporter genes were expressed in various tissues, and a number of genes exhibited tissue-specific expression patterns. Several genes including GmSTP21, GmSFP8, and GmPLT5/6/7/8/9 were predominantly expressed in nodules, and GmPLT8 was significantly induced by rhizobia inoculation in root hairs. Transcript profiling and qRT-PCR analyses suggested that half of these sugar transporter genes were significantly induced or repressed under stresses like salt, drought, and cold. In addition, GmSTP22 was found to be localized in the plasma membrane, and its overexpression promoted plant growth and salt tolerance in transgenic Arabidopsis under the supplement with glucose or sucrose. This study provides insights into the evolutionary expansion, expression pattern and functional divergence of sugar transporter gene family, and will enable further understanding of their biological functions in the regulation of growth, yield formation and stress resistance of soybean.