A deeper root system can improve the efficiency of water and nutrient absorption from soil; therefore, genetic improvements to the root length of crops are essential for yield stability under drought stress. We previously identified a stable quantitative trait locus (QTL) qRLP12 for root length under polyethylene glycol (PEG)-induced drought stress in a Jinhuangma (JHM, sensitive)/Zhushanbai (ZSB, tolerant) recombinant inbred line (RIL) population. To validate and fine map this QTL, in this study, a secondary F₂ population was constructed, and the genetic effect of the target QTL was validated by comparing the phenotype data of different genotypes. Using newly developed markers, 14 genotypes of recombinant F₂ individuals were obtained. A phenotypic analysis of homozygous recombinant progeny lines narrowed qRLP12 to a 91 kb region. Seven putative predicted genes were identified in the target region, among which LOC105165547, a callose synthase gene, was the only one containing nonsynonymous variations in the coding region between two parents. Quantitative real-time PCR analysis revealed that LOC105165547 was significantly induced by PEG stress in the qRLP12+ line. These indicated that LOC105165547 might be the candidate gene for qRLP12, which is responsible for root length subjected to PEG stress. Our results provide a favored gene resource for improving root length under drought stress in sesame.

Sesame is a thermophilic oilseed crop that is vulnerable to low-temperature stress. SWEET sugar transporters are important for sugar allocation, but their roles in sesame cold responses remain poorly understood. In this study, 24 SWEET genes were identified in the sesame genome and classified into six conserved groups with high structural conservation and limited duplication. Comparative transcriptomic and metabolomic analyses of cold-tolerant and cold-sensitive sesame accessions under chilling stress revealed distinct SiSWEET expression patterns and contrasting soluble sugar accumulation. Several SiSWEET genes showed significant correlations with glucose, fructose, and sucrose contents. These results suggest that SWEET-mediated sugar transport is involved in sesame chilling responses and provide candidate genes for improving cold tolerance.

Auxin response factors (ARFs) are pivotal regulators mediating plant growth, development, and abiotic stress responses, especially during seed germination under stressful conditions. However, the ARF gene family has not been thoroughly studied or characterized in sesame. The identification and characterization of ARF family members in the sesame genome were analyzed by bioinformatics methods, and the expression patterns of sesame ARF genes were assessed by quantitative real-time PCR. In this study, a total of 23 ARF genes were identified in the sesame genome, distributed unevenly across 12 chromosomes. Additionally, 15 segmental duplication events were detected. Phylogenetic analysis classified the SiARF genes into four subfamilies, with members within each subgroup sharing conserved structural features and motif compositions. Promoter analysis revealed multiple cis-acting elements associated with plant growth, phytohormone responses, and stress responses. Expression profiling demonstrated distinct tissue-specific expression patterns among the SiARF genes. Notably, SiARF5 and SiARF15 showed predominant expression in seeds 5 days after pollination, whereas SiARF14 exhibited broad expression in roots, stems, leaves, and seeds germinated for 24 h. QRT-PCR analysis identified eight SiARF genes exhibiting biphasic expression patterns during seed germination under abiotic stresses, characterized by initial downregulation and subsequent upregulation. Among them, SiARF11 showed significant induction under all three stress conditions, while SiARF9 was specifically upregulated under salt stress, suggesting their critical roles in stress response regulation. These findings provide a foundation for further investigation into Auxin-mediated responses to abiotic stress during seed germination in sesame.

Introduction: The genus Sesamum (Pedaliaceae) comprises a wide range of cultivated and wild species. Sesame ( Sesamum indicum ) is recognized as one of the oldest oilseed crops cultivated worldwide, whereas S. schinzianum is a wild relative closely associated with the evolutionary history of cultivated sesame. Although the nuclear and chloroplast genomes of Sesamum species have been investigated in previous studies, mitochondrial genome evolution within the genus has received relatively limited attention. Methods: In this study, we assembled and comparatively analyzed the mitochondrial genomes of S. indicum and S. schinzianum by integrating BGI short-read sequencing and Oxford Nanopore long-read sequencing data. Genome assembly was performed using Flye and Unicycler, and annotation was conducted using PMGA together with manual curation. Comparative analyses were then carried out to examine genome organization, gene content, repetitive sequences, codon usage, RNA editing sites, chloroplast-derived sequences, phylogenetic relationships, and collinearity patterns. Results: The mitochondrial genomes of S. indicum and S. schinzianum were assembled into one circular molecule and two major circular contigs, respectively, and both contained 36 conserved protein-coding genes. Abundant simple sequence repeats dominated by tetranucleotide motifs and notable repeat variation were detected. Codon usage showed moderate bias, and 478 and 455 RNA editing sites were predicted in S. indicum and S. schinzianum , respectively. Chloroplast-derived sequences accounted for 8.50% and 6.96% of the mitochondrial genomes, respectively. Phylogenetic and collinearity analyses supported a close relationship between the two Sesamum species and identified synteny-based structural differences between their mitogenomes. Comparative analysis of mitochondrial- and chloroplast-based phylogenies showed that the two datasets were largely congruent at the family level and consistently supported the close relationship between the two Sesamum species, although they differed in the placement of several deeper lineages. Discussion: These results suggest that Sesamum mitogenomes retain conserved gene content while showing assembly- and synteny-supported structural differences. This study provides useful genomic resources for comparative and evolutionary studies of mitochondrial genomes in Pedaliaceae.

Sesame is an important oilseed crop, but its germination stage growth is increasingly limited by heat stress under climate warming. However, the molecular responses underlying heat tolerance in sesame germination stage remain unclear. In this study, a heat-tolerant genotype (G14) and a heat-sensitive genotype (G9) were compared under different durations of high-temperature treatment using phenotypic, metabolomic, and transcriptomic analyses. The results showed that G14 maintained better growth than G9 under both normal and heat stress conditions, with a more pronounced advantage under high temperature. G14 also accumulated lower levels of hydrogen peroxide (H ₂ O ₂ ) under heat stress, suggesting reduced oxidative damage and enhanced heat tolerance. Metabolomic analysis showed that differentially accumulated metabolites (DAMs) in G14 were mainly enriched in lipid metabolism, antioxidant systems, and secondary metabolism, which were activated at early stages and maintained throughout heat stress. In contrast, DAMs in G9 were primarily associated with hormone signaling, carbon metabolism, energy metabolism, and vitamin metabolism. Transcriptomic analysis further showed that heat stress induced extensive changes in gene expression. KEGG enrichment analysis suggested that differentially expressed genes (DEGs) in G14 were mainly involved in maintaining key physiological processes, including photosynthesis, protein processing, and lipid metabolism, whereas those in G9 were predominantly associated with defense and signaling pathways. Integrated metabolomic and transcriptomic analyses supported these patterns and indicated a close coordination between gene expression and metabolic changes. Transcription factor analysis identified members of the ERF and bHLH families as candidate transcription factors associated with the heat stress response in sesame. These findings provide new insights into the molecular responses underlying heat tolerance during sesame germination.