Soybean is one of the most important food crops worldwide.  Like other legumes, soybean can form symbiotic relationships with Rhizobium species.  Nitrogen fixation of soybean via its symbiosis with Rhizobium is pivotal for sustainable agriculture.  Type III effectors (T3Es) are essential regulators of the establishment of the symbiosis, and nodule number is a feature of nitrogen-affected nodulation.  However, genes encoding T3Es at quantitative trait loci (QTLs) related to nodulation have rarely been identified. Chromosome segment substitution lines (CSSLs) have a common genetic background but only a few loci with heterogeneous genetic information; thus, they are suitable materials for identifying candidate genes at a target locus.  In this study, a CSSL population was used to identify the QTLs related to nodule number in soybean.  Single nucleotide polymorphism (SNP) markers and candidate genes within the QTLs interval were detected, and it was determined which genes showed differential expression between isolines.  Four candidate genes (GmCDPK28, GmNAC1, GmbHLH, and GmERF5) linked to the SNPs were identified as being related to nodule traits and pivotal processes and pathways involved in symbiosis establishment.  A candidate gene (GmERF5) encoding a transcription factor that may interact directly with the T3E NopAA was identified.  The confirmed CSSLs with important segments and candidate genes identified in this study are valuable resources for further studies on the genetic network and T3Es involved in the signaling pathway that is essential for symbiosis establishment. 

Soluble sugar content in seeds is an important quality trait of soybean.  In this study, 57 quantitative trait loci (QTLs) related to soluble sugar contents in soybean seeds were collected from databases and published papers.  After meta-overview-collinearity integrated analysis to refine QTL intervals, eight consensus QTLs were identified.  To further verify the consensus QTLs, a population of chromosome segment substitution lines (CSSLs) was analyzed.  Two lines containing fragments covering the regions of consensus QTLs and the recurrent parent were selected: one line showed high soluble sugar contents associated with a consensus QTL fragment, and the other line showed low soluble sugar contents.  Transcriptome sequencing was conducted for these two lines at the early, middle, and late stages of seed development, which identified 158, 109 and 329 differentially expressed genes, respectively.  Based on the analyses of re-sequencing data of the CSSLs and the consensus QTL region, three candidate genes (Glyma.19G146800, Glyma.19G122500, and Glyma.19G128500) were identified in the genetic fragments introduced from wild soybean.  Sequence comparisons between the two CSSL parents SN14 and ZYD00006 revealed a single nucleotide polymorphism (SNP) mutation in the coding sequence of Glyma.19G122500, causing a non-synonymous mutation in the amino acid sequence that affected the predicted protein structure.  A Kompetitive allele-specific PCR (KASP) marker was developed based on this SNP and used to evaluate the CSSLs.  These results lay the foundation for further research to identify genes related to soluble sugar contents in soybean seeds and for future soybean breeding.

The composition and quantity of amino acids influence the protein content and nutritional value of soybeans and also have an important impact upon soybean quality.  After integrating and proofreading 140 original QTLs associated with amino acid contentfrom soybase (http://www.soybase.org/), 138 QTLs were further analyzed to determine high-confidence QTL regions.  Meta-analysis was first carried out using the BioMercator ver. 2.1 software, yielding 33 consensus QTLs.  The consensus QTL confidence intervals (CIs) ranged from 0.07 to 19.85 Mb.  Next, the overview method was used to optimize the CIs, and 57 “real” QTLs were mapped.  Candidate genes in the consensus QTL regions were obtained from Phytozome and were annotated using the Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), Swissprot, and gene annotation databases.  Finally, 16 unpublished candidate genes controlling the content of five types of amino acids were identified with Blast.  These results laid the foundation for fine mapping of soybean amino acid-related QTLs and marker-assisted selection.

    Obtaining transgenic plants is a common method for analyzing gene function. Unfortunately, stable genetic transformation is difficult to achieve, especially for plants (e.g., soybean), which are recalcitrant to genetic transformation. Transient expression systems, such as Arabidopsis protoplast, Nicotiana leaves, and onion bulb leaves are widely used for gene functional studies. A simple method for obtaining transgenic soybean callus tissues was reported recently. We extend this system with simplified culture conditions to gene functional studies, including promoter analysis, expression and subcellular localization of the target protein, and protein-protein interaction. We also evaluate the plasticity of this system with soybean varieties, different vector constructs, and various Agrobacterium strains. The results indicated that the callus transformation system is efficient and adaptable for gene functional investigation in soybean genotype-, vector-, and Agrobacterium strain-independent modes. We demonstrated an easy set-up and practical homologous strategy for soybean gene functional studies.

Phytophthora root rot is one of the most prevalent diseases in the world, which can infect the seedlings and plants, withsubstantial negative impact on soybean yield and quality. MicroRNAs (miRNAs) are a class of post-transcriptionalregulators of gene expression during growth and development of organisms. A soybean disease-resistance varietySuinong 10 was inoculated with Phytophthora sojae race No. 1, and the specific miRNA resistant expression profile wasacquired by microarray for the first time. Different expressional miRNAs have been found after comparing the results ofthe treated sample with the control sample. Furthermore, the target genes of different expressional miRNAs were predicted.Two miRNAs, cbr-mir-241 and ath-miR854a, regulated the disease-resistance process directly through their targets, someenzymes. Another two miRNAs, gma-miR169a and ath-miR169h, participated in disease-resistance regulation as transcriptionfactors. Similarly, one miRNA, ptc-miR164f, has been reported to regulate the plant development. All of these studieswould be served as the foundation for exploring the resistance mechanism.

Soybean is a major cash crop in the world, and its oil content was one of the very important traits. Therefore, the study of gene mapping for oil content in soybean is very important for breeding application. At present, at least 130 QTL loci for soybean oil content have been published; however, the mapping results of oil content were dispersed and a coalescent public map should be established to integrate the published QTLs, and to more efficiently mine genes based on the metaanalysis method of the bioinformatics tools. This study was to construct an integrated map of QTLs for soybean oil content and accelerate the application of bioinformation resource related to oil content improvement in the practice of soybean breeding. We collected information of 130 QTLs reported over the past 20 yr for soybean oil content and used the Software BioMercator 2.1 to project QTLs from their own maps onto a reference map, which was an early-integrated map constructed by Song (2004) for oil-content quantitative trait loci (QTLs) in soybean. Gene mining was performed based on the meta-analysis by running the local ver. GENSCAN and InterProScan. The confidence interval of QTLs was efficaciously narrowed using the meta-analysis method, and 25 consensus QTLs were mapped on the reference map. Using a local version of GENSCAN, 12 805 sequences in the consensus QTL intervals were predicted. With BLAST, these predicted sequences were aligned to gene sequences from the International Protein Index database using InterProScan locally. Thirteen predicted genes were in the class of the geme ontology (GO) accession (0006631), which were involved in the fatty acid metabolic process. These genes were analyzed using BLAST at the NCBI website to examine whether they were related to oil content. Six genes were found in the oil-synthesis pathway. Twenty-five consensus QTLs and six genes were found in the oil-synthesis pathway. These results would lay the foundation for marker-assisted selection and mapping QTL precisely, and these genes will facilitate the researches on the gene mining of oil synthesis and molecular breeding in soybean.