Elevated carbon dioxide concentrations can mitigate the significant threats of high-temperature stress to the yield and quality of cucumber fruit during summer. This study aims to elucidate the response mechanisms of cucumber fruit metabolomics under elevated CO₂ and high-temperature stress while also exploring the potential benefits of elevated CO₂ in mitigating the adverse effects of high temperatures. The fruits of the experimental material cucumber (Cucumis sativus L., ’Jinyou 35’) were grown under soil conditions in the greenhouse. We used untargeted metabolomics methods to analyze the effects of varying temperatures (normal temperatures of 25 to 35 °C and high temperatures of 35 to 45 °C) and CO₂ concentrations (400 ± 20 µmol/mol and 1200 ± 20 µmol/mol) on the morpho-physiological traits, yield-associated traits, and metabolomic profiles of cucumber fruits. The results showed that, under high-temperature stress, elevated carbon dioxide concentrations altered 27 differential metabolites, including tyramine, xylitol, linolenic acid, L-asparagine, α-linolenic acid, and L-phenylalanine. These alterations are associated with the metabolic pathways of alanine, aspartate, glutamate, glutathione, glyoxylate, and dicarboxylic acids. Compared to adding carbon dioxide at normal temperatures, elevated carbon dioxide at high temperatures modified 38 differential metabolites, including vitamin B6, L-citrulline, inositol, L-aspartic acid, sucrose, and palmitic acid. These modifications were linked to the galactose metabolic pathway and the zeatin and arginine biosynthetic pathways. The accumulation of cysteine, glutamic acid, and glycine is essential to form the antioxidant glutathione; thus, cucumber fruits with a higher amino acid content exhibit an enhanced capacity to withstand severe high-temperature stress. Under high-temperature conditions, elevated carbon dioxide adds complexity to changes in differential metabolites within cucumber fruits. These fruits accumulate sugars, organic acids, and amino acids through the galactose metabolism pathway (map00052), the arginine biosynthesis pathway (map00220), and the glutamate synthesis pathway (map00250), thereby improving their heat resistance.

The sunflower, an important oilseed crop and food source across the world, is susceptible to several pathogens, which cause severe losses in sunflower production. The utilization of genetic resistance is the most economical, effective measure to prevent infectious diseases. Based on the sunflower pangenome, in this study, we explored the variability of resistance gene analogs (RGAs) within the species. According to a comparative analysis of RGA candidates in the sunflower pangenome using the RGAugury pipeline, a total of 1344 RGAs were identified, comprising 1107 conserved, 199 varied, and 38 rare RGAs. We also identified RGAs associated with resistance against Sclerotinia sclerotiorum (S. sclerotiorum) in sunflower at the quantitative trait locus (QTL). A total of 61 RGAs were found to be located at four quantitative trait loci (QTLs). Through a detailed expression analysis of RGAs in one susceptible and two tolerant sunflower inbred lines (ILs) across various time points post inoculation, we discovered that 348 RGAs exhibited differential expression in response to Sclerotinia head rot (SHR), with 17 of these differentially expressed RGAs being situated within the QTL regions. In addition, 15 RGA candidates had gene introgression. Our data provide a better understanding of RGAs, which facilitate genomics-based improvements in disease resistance in sunflower.

Elevated carbon dioxide concentrations can mitigate significant threats posed by high-temperature stress to cucumber fruit yield and quality during summer. To investigate the potential metabolic mechanisms, this study employed untargeted metabolomics methods to analyze the effects of varying temperatures and carbon dioxide concentrations on the metabolomic profiles of cucumber fruits. Under high-temperature stress, elevated carbon dioxide concentrations altered 27 differential metabolites, including tyramine, xylitol, linolenic acid, L-asparagine, α-linolenic acid, and L-phenylalanine. These alterations are associated with the metabolic pathways of alanine, aspartate, glutamate, glutathione, glyoxylate, and dicarboxylic acids. Compared to the addition of carbon dioxide at normal temperatures, elevated carbon dioxide at high temperatures modified 38 differential metabolites, including vitamin B6, L-citrulline, inositol, L-aspartic acid, sucrose, and palmitic acid. These modifications were linked to the galactose metabolic pathway and the zeatin and arginine biosynthetic pathways. The accumulation of cysteine, glutamic acid, and glycine is essential for the formation of antioxidant glutathione; thus, cucumber fruits with higher amino acid content exhibit an enhanced capacity to withstand severe high-temperature stress. Under high-temperature conditions, elevated carbon dioxide adds complexity to the changes in differential metabolites within cucumber fruits. These fruits accumulate sugars, organic acids, and amino acids through the galactose metabolism pathway (map00052), the arginine biosynthesis pathway (map00220), and the glutamate synthesis pathway (map00250), thereby improving their heat resistance.