Potassium (K) is known for alleviating the negative effects of abiotic stresses on plants. To explore the functions of K in controlling reactive oxygen species (ROS), antioxidant activities, and osmoregulation in sesame under drought stress, a pot experiment was conducted with three K levels (0, 60, and 120 kg ha^–1, recorded as K0, K1, and K2, respectively) and exposed to well-watered (WW, 75% ± 5% soil relative water content) and drought-stressed (DS, 50% ± 5% soil relative water content) conditions. The results showed that DS stimulated the production of ROS such as increased hydrogen peroxide (H₂O₂), leading to lipid peroxidation as characterized by higher malondialdehyde (MDA) and, consequently, resulting in the decline in relative water content (RWC) and photosynthetic pigments as compared with WW plants. These adverse effects were exacerbated when drought stress was prolonged. Concurrently, K application alleviated the magnitude of decline in the RWC, chlorophyll a, and chlorophyll b, and plants applied with K exhibited superior growth, with the optimal mitigation observed under K2 treatment. Additionally, DS plants treated with K exhibited lower lipid peroxidation, higher antioxidant activities, and increased osmotic solute accumulation in comparison with plants under K deficiency, which suggested that exogenous K application mitigated the oxidative damages and this was more prominent under K2 treatment. Noteworthily, proline and soluble protein, respectively, dominated in the osmotic regulation at 3 and 6 days of drought stress according to the analysis of the quantitative comparison among different osmotically active solutes. Based on the correlation of the aforementioned traits and the analysis of variance on the interaction effects of drought stress and potassium, we propose that superoxide dismutase (SOD), glutathione reductase (GR), and MDA could be critical indicators in balancing ROS detoxification and reproduction. In summary, our studies suggest that optimized K application keeps a balance between the production of antioxidants and ROS and simultaneously affects osmoregulation to alleviate the damage from drought stress.

Background: The adverse effects of climate change on crop production are constraining breeders to develop high-quality environmentally stable varieties. Hence, efforts are being made to identify key genes that could be targeted for enhancing crop tolerance to environmental stresses. ERF transcription factors play an important role in various abiotic stresses in plants. However, the roles of the ERF family in abiotic stresses tolerance are still largely unknown in sesame, the “queen” of oilseed crops. Results: In total, 114 sesame ERF genes (SiERFs) were identified and characterized. 96.49% of the SiERFs were distributed unevenly on the 16 linkage groups of the sesame genome. The phylogenetic analysis with the Arabidopsis ERFs (AtERFs) subdivided SiERF subfamily proteins into 11 subgroups (Groups I to X; and VI-L). Genes in the same subgroup exhibited similar structure and conserved motifs. Evolutionary analysis showed that the expansion of ERF genes in sesame was mainly induced by whole-genome duplication events. Moreover, cis-acting elements analysis showed that SiERFs are mostly involved in environmental responses. Gene expression profiles analysis revealed that 59 and 26 SiERFs are highly stimulated under drought and waterlogging stress, respectively. In addition, qRT-PCR analyses indicated that most of SiERFs are also significantly up-regulated under osmotic, submerge, ABA, and ACC stresses. Among them, SiERF23 and SiERF54 were the most induced by both the abiotic stresses, suggesting their potential for targeted improvement of sesame response to multiple abiotic stresses. Conclusion: This study provides a comprehensive understanding of the structure, classification, evolution, and abiotic stresses response of ERF genes in sesame. Moreover, it offers valuable gene resources for functional characterization towards enhancing sesame tolerance to multiple abiotic stresses.

Cultivating high nitrogen use efficient varieties is a sustainable solution to mitigating adverse effects on the environment caused by excessive nitrogen fertilizer application. However, in sesame, although immoderate nitrogen fertilizers are used to promote yield, the molecular basis of high nitrogen use efficiency (NUE) is largely unknown. Hence, this study aimed to identify high NUE black sesame variety and dissect the underlying physiological and molecular mechanisms. To achieve this, seventeen seedling traits of 30 black sesame varieties were evaluated under low nitrogen (LN) and high nitrogen (HN) conditions. Dry matter accumulation, root parameters, shoot nitrogen accumulation, and chlorophyll content are important factors for evaluating the NUE of sesame genotypes. The variety 17-156 was identified as the most efficient for N utilization. Comparative physiological and transcriptomics analyses revealed that 17-156 possesses a sophisticated nitrogen metabolizing machinery to uptake and assimilate higher quantities of inorganic nitrogen into amino acids and proteins, and simultaneously improving carbon metabolism and growth. Specifically, the total nitrogen and soluble protein contents significantly increased with the increase in nitrogen concentrations. Many important genes, including nitrate transporters (NPFs), amino acid metabolism-related (GS, GOGAT, GDH, etc.), phytohormone-related, and transcription factors, were significantly up-regulated in 17-156 under HN condition. In addition, 38 potential candidate genes were identified for future studies toward improving sesame's NUE. These findings offer valuable resources for deciphering the regulatory network of nitrogen metabolism and developing sesame cultivars with improved NUE.