Multidrug and toxic compound extrusion (MATE) family is an important group of the multidrug efflux transporters that extrude organic compounds, transporting a broad range of substrates such as organic acids, plant hormones and secondary metabolites. However, genome-wide analysis of MATE family in plant species is limited and no such studies have been reported in soybean. A total of 117 genes encoding MATE transporters were identified from the whole genome sequence of soybean (Glycine max), which were denominated as GmMATE1 - GmMATE117. These 117 GmMATE genes were unevenly localized on soybean chromosomes 1 to 20, with both tandem and segmental duplication events detected, and most genes showed tissue-specific expression patterns. Soybean MATE family could be classified into four subfamilies comprising ten smaller subgroups, with diverse potential functions such as transport and accumulation of flavonoids or alkaloids, extrusion of plant-derived or xenobiotic compounds, regulation of disease resistance, and response to abiotic stresses. Eight soybean MATE transporters clustered together with the previously reported MATE proteins related to aluminum (Al) detoxification and iron translocation were further analyzed. Seven stress-responsive cis-elements such as ABRE, ARE, HSE, LTR, MBS, as well as a cis-element of ART1 (Al resistance transcription factor 1), GGNVS, were identified in the upstream region of these eight GmMATE genes. Differential gene expression analysis of these eight GmMATE genes in response to Al stress helps us identify GmMATE75 as the candidate gene for Al tolerance in soybean, whose relative transcript abundance increased at 6, 12 and 24 h after Al treatment, with more fold changes in Al-tolerant than Al-sensitive cultivar, which is consistent with previously reported Al-tolerance related MATE genes. A total of 117 MATE transporters were identified in soybean and their potential functions were proposed by phylogenetic analysis with known plant MATE transporters. The cis-elements and expression patterns of eight soybean MATE genes related to Al detoxification/iron translocation were analyzed, and GmMATE75 was identified as a candidate gene for Al tolerance in soybean. This study provides a first insight on soybean MATE family and their potential roles in soybean response to abiotic stresses especially Al toxicity.

From 1,417 leaf samples with Soybean mosaic virus (SMV)-like symptoms collected from about 1,500 fields of 117 counties of 13 provinces in Southern China during 2004 to 2006, 201 SMV isolates were obtained after biological purification with single-lesion isolation and serological determination. Based on disease reactions on 10 differentials used in China as a representative from various reported differential cultivar systems, the isolates were grouped into 12 strains. Among them, eight were the same as those previously reported from Northeast China and the Huang-Huai Valleys while the other four were new and were designated as SC18, SC19, SC20, and SC21. Strains SC15 and SC18, which were predominant and widespread in Southern China, accounted for 32.3 and 26.4% of the total isolates and were distributed in 9 and 10 provinces, respectively. Thus far, 21 strains have been identified in the three soybean-producing regions in China under the uniform differentials system. According to their responses on the 10 differentials, the strains were clustered into five groups at similarity coefficient 0.6. Among them, SC15 in cluster V is the most virulent strain because it infects all differentials. Therefore, specific attention should be placed on control of its prevalence in soybean production.

Plant U-box (PUB) E3 ubiquitin ligases play important roles in hormone signaling pathway and response to abiotic stresses, but little is known about them in soybean, Glycine max. Here, we identified and characterized 125 PUB genes from the soybean genome, which were classified into eight groups according to their protein domains. Soybean PUB genes (GmPUBs) are broadly expressed in many tissues with a little more abundant in the roots than others. Nine GmPUB genes, GmPUB1-GmPUB9, showed induced expression patterns by drought, and the expression of GmPUB8 was also induced by exogenous abscisic acid (ABA) and NaCl. GmPUB8 was localized to post-Golgi compartments, interacting with GmE2 protein as demonstrated by yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) experiments, and showed E3 ubiquitin ligase activity by in vitro ubiquitination assay. Heterogeneous overexpression of GmPUB8 in Arabidopsis showed decreased drought tolerance, enhanced sensitivity with respect to osmotic- and salt-stress inhibition of seed germination and seedling growth, and inhibited ABA- and mannitol-mediated stomatal closure. Eight drought stress-related genes were less induced in GmPUB8-overexpressing Arabidopsis after drought treatment comparing with the wild-type and pub23 mutant. Taken together, our results suggested that GmPUB8 might negatively regulate plant response to drought stress. In addition, Y2H and BiFC showed GmPUB8 interacted with soybean COL (CONSTANS LIKE) protein. GmPUB8-overexpressing Arabidopsis flowered earlier under middle- and short-day but later under long-day condition, indicating that GmPUB8 might regulate flowering time in photoperiod pathway. This study helps us to understand the functions of PUB E3 ubiquitin ligases in soybean.

Peroxidases play prominent roles in antioxidant responses and stress tolerance in plants; however, their functions in soybean tolerance to salt stress remain unclear. Here, we investigated the role of a peroxidase gene from the wild soybean (Glycine soja), GsPRX9, in soybean tolerance to salt stress. GsPRX9 gene expression was induced by salt treatment in the roots of both salt-tolerant and -sensitive soybean varieties, and its relative expression level in the roots of salt-tolerant soybean varieties showed a significantly higher increase than in salt-sensitive varieties after NaCl treatment, suggesting its possible role in soybean response to salt stress. GsPRX9-overexpressing yeast (strains of INVSc1 and G19) grew better than the control under salt and H₂O₂ stress, and GsPRX9-overexpressing soybean composite plants showed higher shoot fresh weight and leaf relative water content than control plants after NaCl treatment. Moreover, the GsPRX9-overexpressing soybean hairy roots had higher root fresh weight, primary root length, activities of peroxidase and superoxide dismutase, and glutathione level, but lower H₂O₂ content than those in control roots under salt stress. These findings suggest that the overexpression of the GsPRX9 gene enhanced the salt tolerance and antioxidant response in soybean. This study would provide new insights into the role of peroxidase in plant tolerance to salt stress.