Characterization of SOD and GPX Gene Families in the Soybeans in Response to Drought and Salinity Stresses

Abstract

Plant stresses causing accumulation of reactive oxidative species (ROS) are scavenged by effective antioxidant defense systems. Therefore, the present study performed genome-wide identification of superoxide dismutase (SOD) and glutathione peroxidase (GPX) gene families in cultivated and wild soybeans, and 11 other legume species. We identified a total of 101 and 95 genes of SOD and GPX, respectively, across thirteen legume species. The highest numbers of SODs and GPXs were identified in cultivated (Glycine max) and wild (Glycine soja). A comparative phylogenetic study revealed highest homology among the SODs and GPXs of cultivated and wild soybeans relative to other legumes. The exon/intron structure, motif and synteny blocks were conserved in both soybean species. According to Ka/Ks, purifying the selection played the major evolutionary role in these gene families, and segmental duplication are major driving force for SODs and GPXs expansion. In addition, the qRT-PCR analysis of the G. max and G. soja SOD and GPX genes revealed significant differential expression of these genes in response to oxidative, drought and salinity stresses in root tissue. In conclusion, our study provides new insights for the evolution of SOD and GPX gene families in legumes, and provides resources for further functional characterization of these genes for multiple stresses.

Plant Glutathione Peroxidases: Non-Heme Peroxidases with Large Functional Flexibility as a Core Component of ROS-Processing Mechanisms and Signalling

“…Phylogenetic studies of GPX genes from different plant species showed that their number varies between 2 and 25 [ 39 , 40 , 41 ]. For example, two GPX genes were identified in Physcomitrella patens [ 39 ] and Panax ginseng [ 42 ], three in Hordeum vulgare [ 43 ] and Vigna radiata [ 44 ], four in Pinus tabulaeformis [ 45 ] and Brachypodium distachyon [ 39 ], and five genes in Oryza sativa [ 16 , 39 ], Phoenix dactylifera (date palm) [ 46 ], Populus trichocarpa [ 26 ], Ricinus communis [ 47 ], and Solanum lycopersicum [ 39 ]. Six GPXs are encoded by Cucumis sativus [ 48 ], Citrullus lanatus [ 49 ] and Lotus japonica [ 50 ] genome, seven genes were found in Sorghum bicolor [ 51 ] and Zea mays [ 52 ], while there are eight in Arabidopsis thaliana [ 53 ] and Brassica oleracea [ 40 ].…”

“…In most of the cases, a relatively higher number of GPX genes was found in plants with polyploid genome [ 54 ]. For example, 12 genes were identified in Brassica rapa [ 40 ] and Triticum aestivum [ 55 ], 13 in Gossypium hirsutum [ 54 ] and Glycine max [ 44 ], and 25 GPX genes in Brassica napus [ 40 ].…”

“…According to the conserved domain and gene structure analyses conducted on GPX(L) genes from various species, the plant GPXs can be categorized into four or five main groups [ 44 , 47 , 52 , 54 , 55 , 56 , 57 , 58 ]. Comparison of GPX genes belonging to distinct groups disclosed highly similar motifs and conserved exon-intron arrangement patterns within each group [ 52 ].…”

“…This indicates that their structure and function might have been preserved during evolution, yet several differences were also discovered, like in R. communis and Z. maize [ 47 , 52 ]. Generally, the number of exons ranges between four to six, and introns numbers varied from four to ten but showed significant variability among species (e.g., [ 44 , 52 , 54 , 55 , 58 ]. Deviations might be assigned to gene and whole-genome duplications.…”

“…Deviations might be assigned to gene and whole-genome duplications. Evidence of tandem or segmental duplications has been found at several plant GPXs [ 39 , 40 , 44 , 52 , 53 ]. It was suggested that the gene replication activities might play a crucial role in gene evolution [ 40 ].…”