Integrative transcriptome and metabolome analysis reveals the mechanism of fulvic acid alleviating drought stress in oat

Drought stress inhibits oat growth and yield. The application of fulvic acid (FA) can improve the drought resistance of oats, but the corresponding molecular mechanism of FA-mediated drought resistance remains unclear. Here, we studied the effects of FA on the drought tolerance of oat leaves through physiological, transcriptomic, and metabolomics analyses, and identified FA-induced genes and metabolites related to drought tolerance. Physiological analysis showed that under drought stress, FA increased the relative water and chlorophyll contents of oat leaves, enhanced the activity of antioxidant enzymes (SOD, POD, PAL, CAT and 4CL), inhibited the accumulation of malondialdehyde (MDA), hydrogen peroxide (H2O2) and dehydroascorbic acid (DHA), reduced the degree of oxidative damage in oat leaves, improved the drought resistance of oats, and promoted the growth of oat plants. Transcriptome and metabolite analyses revealed 652 differentially expressed genes (DEGs) and 571 differentially expressed metabolites (DEMs) in FA-treated oat leaves under drought stress. These DEGs and DEMs are involved in a variety of biological processes, such as phenylspropanoid biosynthesis and glutathione metabolism pathways. Additionally, FA may be involved in regulating the role of DEGs and DEMs in phenylpropanoid biosynthesis and glutathione metabolism under drought stress. In conclusion, our results suggest that FA promotes oat growth under drought stress by attenuating membrane lipid peroxidation and regulating the antioxidant system, phenylpropanoid biosynthesis, and glutathione metabolism pathways in oat leaves. This study provides new insights into the complex mechanisms by which FA improves drought tolerance in crops

Utilizing Multi-Omics Analysis to Elucidate the Molecular Mechanisms of Oat Responses to Drought Stress

The oat is a crop and forage species with rich nutritional value, capable of adapting to various harsh growing environments, including dry and poor soils. It plays an important role in agricultural production and sustainable development. However, the molecular mechanisms underlying the responses of oat to drought stress remain unclear, warranting further research. In this study, we conducted a pot experiment with the drought-resistant cultivar JiaYan 2 (JIA2) and water-sensitive cultivar BaYou 9 (BA9) during the booting stage under three water gradient treatment conditions: 30% field capacity (severe stress), 45% field capacity (moderate stress), and 70% field capacity (normal water supply). After 7 days of stress, root samples were collected for transcriptome and proteome analyses. Transcriptome analysis revealed that under moderate stress, JIA2 upregulated 1086 differential genes and downregulated 2919 differential genes, while under severe stress, it upregulated 1792 differential genes and downregulated 4729 differential genes. Under moderate stress, BA9 exhibited an upregulation of 395 differential genes, a downregulation of 669, and an upregulation of 886 differential genes, and it exhibited 439 downregulations under severe stress. Under drought stress, most of the differentially expressed genes (DEGs) specific to JIA2 were downregulated, mainly involving redox reactions, carbohydrate metabolism, plant hormone signal regulation, and secondary metabolism. Proteomic analysis revealed that in JIA2, under moderate stress, 489 differential proteins were upregulated and 394 were downregulated, while 493 differential proteins were upregulated and 701 were downregulated under severe stress. In BA9, 590 and 397 differential proteins were upregulated under moderate stress, with 126 and 75 upregulated differential proteins under severe stress. Correlation analysis between transcriptomics and proteomics demonstrated that compared with no drought stress, four types of differentially expressed proteins (DEPs) were identified in the JIA2 differential gene–protein interaction network analysis under severe stress. These included 13 key cor DEGs and DEPs related to plant hormone signal transduction, biosynthesis of secondary metabolites, carbohydrate metabolism processes, and metabolic pathways. The consistency of gene and protein expression was validated using qRT-PCR, indicating their key roles in the strong drought resistance of JIA2

Integrative Transcriptome and Metabolome Analyses of the Interaction of Oat–Oat Stem Rust

Stem rust, caused by Puccinia graminis f. sp. avenae (Pga) Eriks. and E. Henn., is a worldwide and harmful disease of oat (Avena sativa L.). Currently, no resistant varieties are used in production as the molecular resistance mechanism of oat to stem rust remains unclear. Here, oat plants were inoculated with Pga pathogens, and the metabolome and transcriptome of leaves were detected to investigate the molecular and physiological changes. Our results showed that Pga inoculation increased the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and phenylalnine ammonialyase (PAL), which triggered defense responses. The transcriptomic and metabolomic analyses were performed to detect the key genes and metabolites of oat interacting with Pga. We identified 1814 upregulated and 1955 downregulated genes in Pga infected leaves. These genes were mainly involved in the ‘phenylpropanoid biosynthesis’, ‘flavonoid biosynthesis’, and ‘photosynthesis-antenna proteins’. We also detected 162 differential metabolites between Pga-infected and non-infected leaves, including flavonoids and derivatives, amino acids, organic acids, and carbohydrates. The integrated analysis revealed four pathways, including the ‘citrate cycle’, ‘cysteine and methionine metabolism’, ‘tryptophan metabolism’, and ‘glyoxylate and dicarboxylate metabolism’. The networks for these pathways were subsequently constructed. Overall, the results suggested that oat plants fight against Pga by activating the metabolism of amino acids, organic acids, and flavonoids. This study provides valuable molecular information about the response of oat to Pga infection

Label-Free Proteomics Reveals the Response of Oat (Avena sativa L.) Seedling Root Respiratory Metabolism to Salt Stress

Soil salinity is among the crucial factors influencing agricultural productivity of crops, including oat. The respiratory metabolic pathways are of great significance for plants to adapt to salt stress, but current research is limited and there are few reports on salt-tolerant crops such as oat, which is necessary to conduct in-depth research. In this study, we conducted a pot experiment to determine the effects of salt stress on oat root growth and respiratory metabolism. Three salt stress levels—control (CK), moderate, and severe—were applied to compare the salt tolerance of the salt-tolerant cultivar Bai2 and the salt-sensitive cultivar Bai5. We selected oat roots at the seedling stage as the research focus and analyzed fresh root samples using an Oxytherm liquid-phase oxygen electrode, a digital scanner, and proteomics. The results showed that with an increased concentration of salt stress, the dry and fresh weight, root–shoot ratio, total root length, root surface area, root volume, and average diameter of the two oat cultivars showed a decreasing trend. Compared with CK, the total root respiration rate of Bai2 under moderate and severe stress decreased by 15.6% and 28%, respectively, and that of Bai5 decreased by 70.4% and 79.0%, respectively. After quantitative analysis of 18 oat root samples from the 2 cultivars using the label-free method, 7174 differential proteins were identified and 63 differential proteins were obtained, which involved 7 functional categories. In total, 111 differential proteins were specifically expressed in the root of the salt-tolerant cultivar Bai2, involving 12 functional categories. Through interaction network analysis, the proteins differentially expressed between the salt treatment and CK groups of the salt-tolerant cultivar Bai2 were analyzed. In total, five types of differentially expressed proteins interacting with each other were detected; these mainly involved antioxidant enzymes, pyruvate metabolism, glycolysis, tricarboxylic acid cycle, and energy metabolism pathways. Salt stress promoted the respiration rate of oat root glycolysis. The respiration rate of the tricarboxylic acid pathway decreased with increased salt stress concentration, while the respiration rate of the pentose phosphate pathway increased. Compared with CK, following moderate and severe salt stress treatment, alcohol dehydrogenase activity in Bai2 increased by 384% and 145%, respectively, while that of Bai5 increased by 434% and 157%, respectively. At increased salt stress concentrations, Bai2 mainly used pyruvate–ethanol fermentation for anaerobic respiration, while Bai5 mainly used pyruvate–lactic acid fermentation for anaerobic respiration. This significant discovery revealed for the first time from the perspective of respiratory metabolism that different salt-tolerant oat cultivars adapt to salt stress in different ways to maintain normal growth and development. The experimental results provide new insights into plant adaptation to salt stress from the perspective of respiratory metabolism

Effect of bentonite as a soil amendment on field water-holding capacity, and millet photosynthesis and grain quality

AbstractA field experiment was conducted in a semi-arid region in northern China to evaluate the effects of bentonite soil amendment on field water-holding capacity, plant available water, and crop photosynthesis and grain quality parameters for millet [Setaria italic (L.) Beauv.] production over a 5-year period. Treatments included six rates of bentonite amendments (0, 6, 12, 18, 24 and 30 Mg ha−1) applied only once in 2011. The application of bentonite significantly (P &lt; 0.05) increased field water-holding capacity and plant available water in the 0–40 cm layer. Bentonite also significantly (P &lt; 0.05) increased the emergence rate, above-ground dry matter accumulation (AGDM), net photosynthesis rate (Pr), transpiration rate (Tr), soil and plant analysis development (SPAD) and leaf water use efficiency (WUE). It also increased grain quality parameters including grain protein, fat and fiber content. Averaged over all the years, the optimum rate of bentonite was 24 Mg ha−1 for all plant growth and photosynthesis parameters except for grain quality where 18 Mg ha−1 bentonite had the greatest effect. This study suggests that bentonite application in semi-arid regions would have beneficial effects on crop growth and soil water-holding properties.</jats:p

Blending controlled-release urea and urea under ridge-furrow with plastic film mulching improves yield while mitigating carbon footprint in rainfed potato

AbstractRidge-furrow with plastic film mulching and various urea types have been applied in rainfed agriculture, but their interactive effects on potato (Solanum tuberosum L.) yield and especially environments remain poorly understood. A three-year experiment was conducted to explore the responses of tuber yield, methane (CH4) and nitrous oxide (N2O) emissions, net global warming potential (NGWP), carbon footprint (CF), and net ecosystem economic budget (NEEB) of rainfed potato to two mulching practices [plastic film mulching (RM) and no plastic film mulching (NM)] and three urea types [conventional urea (U), controlled-release urea (C), and a mixture of equal amounts of conventional urea and controlled-release urea at a ratio of 1:1 (CU)] and their interactions. The results showed that RM significantly decreased cumulative N2O emissions and CH4 uptake by 4.9% and 28.4%, but significantly increased NGWP by 8.9% relative to NM. Compared with U, the C and CU produced much lower cumulative N2O emissions and NGWP and higher CH4 uptake. The interaction of mulching methods and urea type had significant influence on tuber yield and NEEB. Considering both environment and production, RMCU could not only achieve a high tuber yield and NEEB (by up to 26.5% and 42.9%, respectively), but also reduce the CF (by up to 13.7%), and therefore should be considered an effective strategy for dryland potato.</jats:p

Fulvic Acid Enhances Oat Growth and Grain Yield Under Drought Deficit by Regulating Ascorbate&ndash;Glutathione Cycle, Chlorophyll Synthesis, and Carbon&ndash;Assimilation Ability

Drought deficit inhibits oat growth and yield. Fulvic acid (FA) can enhance plant stress tolerance, but its effects on regulating the ascorbate&ndash;glutathione cycle, chlorophyll synthesis, and carbon&ndash;assimilation ability remain unclear. Therefore, this study aimed to elucidate the physiological mechanisms of the FA regulation of drought tolerance in oats and its relationship with growth and yield using the drought-resistant variety Yanke 2 and the drought-sensitive variety Bayou 9. The effects of FA on growth and yield, the antioxidant system, chlorophyll synthesis, and carbon&ndash;assimilation capacity of oats under drought stress were investigated by systematically assessing changes in morphogenesis, ascorbate&ndash;glutathione cycle, chlorophyll and its intermediates, carbon&ndash;assimilation enzyme activities, and carbohydrate metabolism. The results showed that under drought stress, FA treatment significantly promoted oat growth (leaf area, dry matter) and yield, elevated glutathione peroxidase, ascorbate peroxidase, glutathione reductase, and dehydroascorbate reductase activities, reduced ascorbic acid, and reduced glutathione content. In addition, FA increased chlorophyll, as well as magnesium protoporphyrin IX, protoporphyrin IX, and protochlorophyllin acid ester content, enhanced 1,5-bisphosphate ribulose carboxylase, 1,5-bisphosphate ribulose carboxylase enzyme, 1,7-bisphosphate sestamibiose heptulose esterase, 1,6-bisphosphate fructose aldolase, sucrose synthase, sucrose phosphate synthase, acid invertase, and neutral invertase activities, and increased sucrose, glucose, and fructose content. Overall, fulvic acid (FA) alleviates drought-induced damage in oats by enhancing the ascorbate&ndash;glutathione cycle, promoting chlorophyll biosynthesis, and improving carbon assimilation and carbohydrate metabolism. The drought-sensitive variety (Yanke 2) was more effective in application compared to the drought-resistant variety (Bayou 9). This research provides valuable insight into its potential as a biostimulant under abiotic stress