Jingping Niu

Soluble sugars are essential components in the physiology and metabolism of soybeans (Glycine max), playing a critical role in regulating key processes such as development, germination, and flavor formation. The soluble sugar content in soybean seeds is primarily composed of stachyose, raffinose, sucrose, and glucose. This study aims to elucidate the genetic mechanisms underlying variation in the composition of soluble sugars in soybean seeds. A 128 recombinant inbred line (RIL) population was used, and concentrations of these four sugars were quantified across three years (2015, 2016, and 2017 in Shanxi). The analysis revealed that Jin Da 53 exhibited significantly higher sucrose and total sugar contents compared to Ping Nan, while stachyose levels were notably elevated in Ping Nan. Except for glucose content in 2017 and 2019, the RIL population’s traits all exhibited a normal distribution, making it suitable for QTL analyses. A total of twenty QTLs were identified for the four sugar components: five for glucose, four for raffinose, four for sucrose, three for stachyose, and four for total sugar, all with LOD > 2.5. Notably, three QTLs located on chromosome 10 (S10_37101443-S10_38298307, S10_38681635-S10_39134900, and S10_36697685-S10_36697916) were found to be associated with stachyose content, identifying one candidate gene, Glyma.10g154400, which was implicated in carbohydrate metabolic processes; a QTL located on chromosome 11 (96.881–105.5 cM) was identified in 2019 as a significant locus influencing sucrose content, identifying another candidate gene, Glyma.11g136200, which was linked to sugar/inositol transporter activity. Expression analysis of these candidate genes demonstrated the Glyma.10g154400 gene exhibited higher expression levels in varieties with lower stachyose content, whereas Glyma.11g136200 showed increased expression in lines with elevated sucrose levels. This study provides an important genetic basis for the breeding of soybean varieties with increased sugar content.

Beneficial fungi of the genus Trichoderma are among the most widespread biocontrol agents that induce a plant’s defense response against pathogens. Fusarium solani is one of the main pathogens that can negatively affect Astragalus mongholicus production and quality. To investigate the impact of Trichoderma harzianum on Astragalus mongholicus defense responses to Fusarium solani, A. mongholicus roots under T. harzianum + F. solani (T + F) treatment and F. solani (F) treatment were sampled and subjected to transcriptomic analysis. A differential expression analysis revealed that 6361 differentially expressed genes (DEGs) responded to T. harzianum induction. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of the 6361 DEGs revealed that the genes significantly clustered into resistance-related pathways, such as the plant–pathogen interaction pathway, phenylpropanoid biosynthesis pathway, flavonoid biosynthesis pathway, isoflavonoid biosynthesis pathway, mitogen-activated protein kinase (MAPK) signaling pathway, and plant hormone signal transduction pathway. Pathway analysis revealed that the PR1, formononetin biosynthesis, biochanin A biosynthesis, and CHIB, ROS production, and HSP90 may be upregulated by T. harzianum and play important roles in disease resistance. Our study further revealed that the H₂O₂ content was significantly increased by T. harzianum induction. Formononetin and biochanin A had the potential to suppress F. solani. Weighted gene coexpression network analysis (WGCNA) revealed one module, including 58 DEGs associated with T. harzianum induction. One core hub gene, RPS25, was found to be upregulated by T. harzianum, SA (salicylic acid) and ETH (ethephon). Overall, our data indicate that T. harzianum can induce induced systemic resistance (ISR) and systemic acquired resistance (SAR) in A. mongholicus. The results of this study lay a foundation for a further understanding of the molecular mechanism by which T. harzianum induces resistance in A. mongholicus.

Soybean mosaic virus (SMV) is one of the main pathogens that can negatively affect soybean production and quality. To study the gene regulatory network of soybeans in response to SMV SC15, the resistant line X149 and susceptible line X97 were subjected to transcriptome analysis at 0, 2, 8, 12, 24, and 48 h post-inoculation (hpi). Differential expression analysis revealed that 10,190 differentially expressed genes (DEGs) responded to SC15 infection. Weighted gene co-expression network analysis (WGCNA) was performed to identify highly related resistance gene modules; in total, eight modules, including 2256 DEGs, were identified. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of 2256 DEGs revealed that the genes significantly clustered into resistance-related pathways, such as the plant–pathogen interaction pathway, mitogen-activated protein kinases (MAPK) signaling pathway, and plant hormone signal transduction pathway. Among these pathways, we found that the flg22, Ca²⁺, hydrogen peroxide (H₂O₂), and abscisic acid (ABA) regulatory pathways were fully covered by 36 DEGs. Among the 36 DEGs, the gene Glyma.01G225100 (protein phosphatase 2C, PP2C) in the ABA regulatory pathway, the gene Glyma.16G031900 (WRKY transcription factor 22, WRKY22) in Ca²⁺ and H₂O₂ regulatory pathways, and the gene Glyma.04G175300 (calcium-dependent protein kinase, CDPK) in Ca²⁺ regulatory pathways were highly connected hub genes. These results indicate that the resistance of X149 to SC15 may depend on the positive regulation of flg22, Ca²⁺, H₂O₂, and ABA regulatory pathways. Our study further showed that superoxide dismutase (SOD) activity, H₂O₂ content, and catalase (CAT) and peroxidase (POD) activities were significantly up-regulated in the resistant line X149 compared with those in 0 hpi. This finding indicates that the H₂O₂ regulatory pathway might be dependent on flg22- and Ca²⁺-pathway-induced ROS generation. In addition, two hub genes, Glyma.07G190100 (encoding F-box protein) and Glyma.12G185400 (encoding calmodulin-like proteins, CMLs), were also identified and they could positively regulate X149 resistance. This study provides pathways for further investigation of SMV resistance mechanisms in soybean.

Astragali Radix, derived from the roots of Astragalus mongholicus, is a traditional Chinese medicine containing flavonoids and saponins as its key ingredients. With a shortage in the wild sources of the herbal plant, it is especially important to explore a cultivation mode for A. mongholicus for medicinal purposes. Cutting, a physical environmental stress method, was used in this study with the objective of improving the quality of this herbal legume. We found that cutting of the top 1/3 of the aboveground part of A. mongholicus during the fruiting period resulted in a significant increase in the content of flavonoids and saponins, as well as in root growth, including length, diameter, and dry weight. Furthermore, the leaves were sampled and analyzed using a combined transcriptome and metabolome analysis approach at five different time points after the treatment. Sixteen differentially expressed unigenes (DEGs) involved in the biosynthesis of flavonoids were identified; these were found to stimulate the synthesis of flavonoids such as formononetin and calycosin–7–O–β–D–glucoside. Moreover, we identified 10 DEGs that were associated with the biosynthesis of saponins, including astragaloside IV and soyasaponin I, and found that they only regulated the mevalonic acid (MVA) pathway. These findings provide new insights into cultivating high-quality A. mongholicus, which could potentially alleviate the scarcity of this valuable medicinal plant.