WUSCHEL-related homeobox (WOX) is a family of transcription factors that are unique to plants and is characterized by the presence of a homeodomain. The WOX transcription factor plays an important role in regulating plant growth and development and the response to abiotic stress. Soybean is one of the most important oil crops worldwide. In this study, based on the available genome data of soybean, the WOX gene family was identified by bioinformatics analysis. The chromosome distribution, gene and protein structures, phylogenetic relationship and gene expression patterns of this family were comprehensively compared. The results showed that a total of 33 putative WOX genes in the soybean genome were found and then designated as GmWOX1- GmWOX33, which were distributed across 19 chromosomes except chromosome 16. Multiple sequence analysis of the GmWOX gene family revealed a highly conserved homeodomain. Phylogenetic tree analysis showed that 33 WOX genes could be divided into three major clades (modern/WUS, intermediate and ancient) in soybean. Of these 33 WOX genes, some showed differential expression patterns in the tested tissues (leaves, pods, unopen and open flowers, nodules, seed, roots, root hairs, stems, shoot apical meristems and shoot tips). In addition, the expression profile and qRT-PCR analysis showed that most of the GmWOX genes responded to different abiotic stress treatments (cold and drought). According to the expression pattern of GmWOX genes in the high regeneration capacity soybean material P3, overexpression of GmWOX18 was selected for function analysis. The overexpression of GmWOX18 increased the regeneration ability of clustered buds. The results will provide valuable information for further studies on the roles of WOX genes in regulating soybean growth, development and responses to abiotic stress, as well as a basis for the functional identification and analysis of WOX genes in soybean.

Sucrose metabolism plays a critical role in development, stress response, and yield formation of plants. Sucrose phosphate synthase (SPS) is the key rate-limiting enzyme in the sucrose synthesis pathway. To date, genome-wide survey and comprehensive analysis of the SPS gene family in soybean (Glycine max) have yet to be performed. In this study, seven genes encoding SPS were identified in soybean genome. The structural characteristics, phylogenetics, tissue expression patterns, and cold stress response of these GmSPSs were investigated. A comparative phylogenetic analysis of SPS proteins in soybean, Medicago truncatula, Medicago sativa, Lotus japonicus, Arabidopsis, and rice revealed four families. GmSPSs were clustered into three families from A to C, and have undergone five segmental duplication events under purifying selection. All GmSPS genes had various expression patterns in different tissues, and family A members GmSPS13/17 were highly expressed in nodules. Remarkably, all GmSPS promoters contain multiple low-temperature-responsive elements such as potential binding sites of inducer of CBF expression 1 (ICE1), the central regulator in cold response. qRT-PCR proved that these GmSPS genes, especially GmSPS8/18, were induced by cold treatment in soybean leaves, and the expression pattern of GmICE1 under cold treatment was similar to that of GmSPS8/18. Further transient expression analysis in Nicotiana benthamiana and electrophoretic mobility shift assay (EMSA) indicated that GmSPS8 and GmSPS18 transcriptions were directly activated by GmICE1. Taken together, our findings may aid in future efforts to clarify the potential roles of GmSPS genes in response to cold stress in soybean.

Soybean is an important oil and protein crop in the world. Cotton bollworm (Helicoverpa armigera) is one of primary defoliating insects which seriously damage the soybean production. The wild soybean, ED059, was reported to be highly resistant to H. armigera. However, the molecular mechanism of resistance to H. armigera remains unknown. In this study, we conducted the transcript and protein profilings for ED059 and a susceptible soybean cultivar (cv.) Tianlong 2. In summary, 2213 genes and 116 proteins were specifically expressed in response to H. armigera in ED059, while 2179 genes and 9 proteins were specifically expressed in cv. Tianlong 2. Four hundred and four genes were significantly up-regulated in response to H. armigera in ED059 while down-regulated or not changed in cv. Tianlong 2. GO analyses showed the specifically expressed genes in ED059 were mainly enriched in metabolism-related pathways. The function of one potential resistant gene involved in the phenylpropanoid pathway was confirmed by use of transgenic Arabidopsis. Our study provided useful resources for the soybean improvement, which could contribute to the elucidation of defense mechanisms against chewing insects in plants.