Mitochondrial complex I (CI) is a major source of reactive oxygen species (ROS) in plant cells, and iron–sulfur (Fe-S) cluster proteins are critical for maintaining CI structure and electron transport. C1-FDX, a mitochondrion-localized ferredoxin containing a [2Fe-2S] cluster, acts as a structural component and assembly factor of mitochondrial CI and complex V (CV) in Arabidopsis. In this study, we further characterized the physiological and molecular functions of C1-FDX in regulating ROS production, NADH/NAD⁺ homeostasis, and iron metabolism. Histochemical staining demonstrated that loss of function of C1-FDX in Arabidopsis c1-fdx mutants accumulated excessive superoxide anions (O₂^•−) but exhibited reduced hydrogen peroxide (H₂O₂) relative to the wild type (WT). Biochemical assays further confirmed that there was an elevated NADH/NAD⁺ ratio in mutant seedlings, which facilitated O₂^•− overproduction at mitochondrial CI. Loss of C1-FDX also led to Fe³⁺ accumulation in mutant tissues. Immunoblot and qRT-PCR results showed that the abundance of MnSOD markedly increased, while other antioxidant proteins, including FeSOD, CAT1, and GR, were downregulated in c1-fdx mutants of Arabidopsis. The enhanced MnSOD activity accelerated the conversion of O₂^•− into H₂O₂, and the subsequently accumulated Fe³⁺ may be derived from the Fenton reaction, which consumes H₂O₂, ultimately resulting in decreased H₂O₂ levels. Additionally, deficiency of C1-FDX disturbed the abundance of mitochondrial chaperones, proteases, and alternative respiratory pathway proteins. Collectively, our findings demonstrate that C1-FDX participates in the regulation of mitochondrial ROS balance and iron homeostasis and suggest there is a novel regulatory link between ferredoxin, the electron transport chain, and the Fenton reaction in plant mitochondria.

Background: Heat shock protein 100 (HSP100) is a key molecular chaperone that maintains intracellular proteostasis and enhances plant tolerance. However, the HSP100 gene family in soybean (Glycine max) has not been systematically characterized. Methods: In this study, we performed genome-wide identification and comprehensive analysis of the GmHSP100 gene family and analyzed their phylogeny, genomic distribution, synteny, protein structures, subcellular localization, promoter cis-elements, and expression patterns under heat and salt stresses via bioinformatics approaches and quantitative real-time PCR (qRT-PCR) validation. Results: Thirteen GmHSP100 members were identified, which were classified into CLPB, CLPC and CLPD subfamilies. Segmental and whole-genome duplications primarily drove the expansion of this gene family. All encoded proteins possessed conserved AAA+ ATPase domains, with distinct motifs across subfamilies. Most proteins localized to the cytoplasm, while CLPC and CLPD targeted chloroplasts and GmCLPB4 localized to mitochondria. Promoter analysis identified numerous elements associated with light, hormone and stress responses. Expression profiling showed strong tissue specificity and time-dependent stress-treatment induction. Heat stress triggered rapid and strong upregulation of the GmHSP100s, whereas salt stress salt stress induced their relatively delayed and sustained expression. Conclusions: These findings reveal the evolutionary conservation and diversification of the GmHSP100 gene family in soybean, providing a foundational framework for understanding the functions of GmHSP100 in stress adaptation.

Glycosyltransferases (GTs) are key enzymes that catalyze the transfer of sugar moieties to diverse acceptor molecules and play important roles in a wide range of biological processes, including plant growth, development, and environmental adaptation. However, glycosyltransferase family 4 (GT4), the second-largest GT family, remains poorly characterized in soybean. In this study, we identified 60 GT4 family members in the soybean genome based on sequence information from the CAZy database and systematically characterized their phylogenetic relationships, genomic organization, and expression patterns by integrating genomic and multidimensional transcriptomic data. Furthermore, using a previously established soybean ethyl methanesulfonate (EMS) mutant population, we identified GmSPS8 as a candidate gene potentially involved in the regulation of seed weight. Notably, natural variation and haplotype analyses revealed that GmSPS8 is located within a genomic region subject to domestication selection, suggesting its potential involvement in the evolutionary selection of soybean seed size. In sum, we systematically characterized the soybean GT4 gene family and identified GmSPS8 as a potential domestication-associated candidate gene for seed weight regulation, providing new insights into the functional characterization of soybean GT4 family members and the identification and utilization of genes associated with soybean yield-related traits.