Plant fatty acid desaturases (FADs) catalyze the desaturation of fatty acids in various forms and play important roles in regulating fatty acid composition and maintaining membrane fluidity under temperature stress. A total of 30 FADs were identified from a maize genome, including 13 soluble and 17 membrane-bound FADs, which were further classified into two and five sub-groups, respectively, via phylogenetic analysis. Although there is no evolutionary relationship between the soluble and the membrane-bound FADs, they all harbor a highly conserved FA_desaturase domain, and the types and the distributions of conserved motifs are similar within each sub-group. The transcriptome analysis revealed that genes encoding FADs exhibited different expression profiles under cold and heat stresses. The expression of ZmFAD2.1&2.2, ZmFAD7, and ZmSLD1&3 were significantly up-regulated under cold stress; moreover, the expression of ZmFAD2.1&2.3 and ZmSLD1&3 were obviously down-regulated under heat stress. The co-expression analysis demonstrated close correlation among the transcription factors and the significant responsive FAD genes under cold or heat stress. This study helps to understand the roles of plant FADs in temperature stress responses.

Soybean vegetable oil is an important source of the human diet. However, the analysis of the genetic mechanism leading to changes in soybean oil content is still incomplete. In this study, a total of 227 soybean materials were applied and analyzed by a genome-wide association study (GWAS). There are 44 quantitative trait nucleotides (QTNs) that were identified as associated with oil content. A total of six, four, and 34 significant QTN loci were identified in Xiangyang, Hulan, and Acheng, respectively. Of those, 26 QTNs overlapped with or were near the known oil content quantitative trait locus (QTL), and 18 new QTNs related to oil content were identified. A total of 594 genes were located near the peak single nucleotide polymorphism (SNP) from three tested environments. These candidate genes exhibited significant enrichment in tropane, piperidine, and pyridine alkaloid biosynthesiss (ko00960), ABC transporters (ko02010), photosynthesis-antenna proteins (ko00196), and betalain biosynthesis (ko00965). Combined with the GWAS and weighted gene co-expression network analysis (WGCNA), four candidate genes (Glyma.18G300100, Glyma.11G221100, Glyma.13G343300, and Glyma.02G166100) that may regulate oil content were identified. In addition, Glyma.18G300100 was divided into two main haplotypes in the studied accessions. The oil content of haplotype 1 is significantly lower than that of haplotype 2. Our research findings provide a theoretical basis for improving the regulatory mechanism of soybean oil content.

Long-chain acyl-CoA synthases (LACSs) are a key factor in the formation of acyl-CoA after fatty acid hydrolysis and play an important role in plant stress resistance. This gene family has not been research in soybeans. In this study, the soybean (Glycine max (L.) Merr.) whole genome was identified, the LACS family genes of soybean were screened, and the bioinformatics, tissue expression, abiotic stress, drought stress and co-expression of transcription factors of the gene family were analyzed to preliminarily clarify the function of the LACS family of soybean. A total of 17 LACS genes were screened from soybean genome sequencing data. A bioinformatics analysis of the GmLACS gene was carried out from the aspects of phylogeny, gene structure, conserved sequence and promoter homeopathic element. The transcription spectra of GmLACSs in different organs and abiotic stresses were used by qRT-PCR. The GmLACS genes, which co-expresses the significant response of the analysis of drought stress and transcription factors. The results showed that all soybean LACS have highly conserved AMP-binding domains, and all soybean LACS genes were divided into 6 subfamilies. Transcriptome analysis indicated that the gene-encoding expression profiles under alkali, low temperature, and drought stress. The expression of GmLACS9/15/17 were significantly upregulated under alkali, low temperature and drought stress. Co-expression analysis showed that there was a close correlation between transcription factors and genes that significantly responded to LACS under drought stress. These results provide a theoretical and empirical basis for clarifying the function of LACS family genes and abiotic stress response mechanism of soybean.

Protein content (PC) is crucial to the nutritional quality of soybean [Glycine max (L.) Merrill]. In this study, a total of 266 accessions were used to perform a genome-wide association study (GWAS) in three tested environments. A total of 23,131 high-quality SNP markers (MAF ≥ 0.02, missing data ≤ 10%) were identified. A total of 40 association signals were significantly associated with PC. Among them, five novel quantitative trait nucleotides (QTNs) were discovered, and another 32 QTNs were found to be overlapping with the genomic regions of known quantitative trait loci (QTL) related to soybean PC. Combined with GWAS, metabolome and transcriptome sequencing, 59 differentially expressed genes (DEGs) that might control the change in protein content were identified. Meantime, four commonly upregulated differentially abundant metabolites (DAMs) and 29 commonly downregulated DAMs were found. Remarkably, the soybean gene Glyma.08G136900, which is homologous with Arabidopsis hydroxyproline-rich glycoproteins (HRGPs), may play an important role in improving the PC. Additionally, Glyma.08G136900 was divided into two main haplotype in the tested accessions. The PC of haplotype 1 was significantly lower than that of haplotype 2. The results of this study provided insights into the genetic mechanisms regulating protein content in soybean.

Fatty acid transporters (FAXs) play an important role in fatty acid synthesis by facilitating transport fatty acids from the plastid to the endoplasmic reticulum. This process is essential for providing precursor substances necessary for triglycerides (TAGs). Although FAX genes have been identified in variety of plant species, the identification and molecular functions of the GmFAX gene members in soybean are still unclear. In this study, soybean FAX genes were identified through the utilization of the Phytozome (v13) and NCBI online websites. Subsequently, phylogenetic trees, expression patterns, gene structures, and qRT-PCR were analyzed. A total of eight GmFAX members were identified at the whole genome level, and further phylogenetic analysis revealed that these members can be categorized into four subfamilies. In addition, all members of GmFAX contain a highly conserved domain Tmemb_14. Through qRT-PCR analysis, it was found that the expression level of the GmFAX8 gene is relatively high in leaves and stems. Further investigation revealed that the total fatty acid content in hairy roots overexpressing the GmFAX8 gene was significantly greater than that observed in the control strain. The results presented above suggest that the GmFAX8 gene may play an important role in the accumulation of oil within soybeans.

Phosphofructokinase (PFK), a core metabolic enzyme conserved across all organisms, plays a pivotal role in plant growth and development as well as in the regulation of responses to abiotic stresses. While the PFK gene family has been characterized in a variety of plant species and a partial identification in soybean has been reported recently, the complete repertoire and the functional roles of this gene family in soybean remain to be fully elucidated, with inconsistencies in gene number observed across different studies. In this study, we further performed a systematic genome-wide screening of soybean and identified a total of 27 GmPFK family members. Phylogenetic tree analysis further classified these members into three distinct subfamilies. Conserved structure analysis revealed that all GmPFKs contain the PFK domain (PF00365). Real-time quantitative PCR (qRT-PCR) analysis demonstrated that the GmPFK6 gene exhibited a significant upregulation of expression under salt stress. Furthermore, the GmPFK6 gene was cloned and introduced into soybean hairy roots. The results demonstrated that under salt stress, the root length and fresh weight of hairy roots from the control lines were significantly greater than those from the transgenic lines. In addition, under salt stress, the superoxide dismutase (SOD) activity in the control lines was significantly higher than that in the transgenic lines, while the malondialdehyde (MDA) content in the transgenic lines was significantly lower than that in the control lines.