Monogalactosyldiacylglycerol (MGDG), as the primary lipid component of thylakoid membranes, has a significant part in plant growth and stress response. The current study employed two transgenic wheat lines (MG1516 and MG1314) overexpressing the MGDG synthase gene (TaMGD) and wild-type cv "JW1" to explore the function of TaMGD in response to high temperature stress during the anthesis stage of wheat. Under high-temperature stress, the overexpressed wheat lines exhibited higher grain weight, increased antioxidant enzyme activity, and lower H₂O₂ and malondialdehyde contents in leaves. Transcriptomic analysis suggests that overexpression of TaMGD influenced multiple metabolic pathways in response to high-temperature stress, including carbon metabolism, amino acid metabolism, photosynthesis, and lipid-related metabolism. Overall, 146 differentially expressed metabolites (DEMs) were identified in MG1516 and wild-type (WT) under heat stress, with MG1516 exhibiting a higher number of upregulated metabolites, particularly glycolipids, organic acids, and organic oxygen compounds. Furthermore, lipid content and unsaturation analysis revealed that the overexpressing wheat line had a higher lipid content and greater saturation than WT under heat stress. Our findings demonstrate that overexpression of TaMGD in wheat affects multiple metabolic pathways, including photosynthesis, carbon, and amino acid metabolism, in reply to high-temperature stress through the modification of cell membrane lipid content, fatty acid unsaturation and other factors.

Understanding the physicochemical properties of starch during grain development and the mechanism for resistant starch (RS) accumulation will provide useful information for improving the RS content of wheat. The grains from wheat mutant lines with high RS contents and their corresponding wild-type control were analyzed to characterize the structural and physicochemical properties of wheat starch. A transcriptomic analysis was used to analyze the differentially expressed genes (DEGs) involved in RS accumulation. The results showed that the RS content increased with grain development, along with the total starch content, but a larger increase was observed in the middle and later stages of grain filling. The X-ray diffraction peak intensity and relative crystallinity of starch exhibited the lowest and highest values at 10 days after anthesis, respectively. Regarding the thermal properties of starch, the peak temperature and conclusion temperature generally decreased with grain development; however, the enthalpy values showed no apparent regularity. Compared to control cultivar ZM22, the RS639 and RS683 lines with high RS contents showed high amylose contents and high relative crystallinity and a large proportion of 2.0~9.8 µm starch granules. Furthermore, the transcriptomics analysis revealed that the average relative expression of the glucan-branching enzyme (GBE) α-1,4 glucan phosphorylase (Pho) and starch synthase (SS) in ZM22 was 2.47-, 2.70-, and 2.56-fold higher than that in RS639, respectively; which indicates that the downregulation of the expression of genes encoding GBE, Pho, and SS in wheat grain promotes the accumulation of RS.

This study uses proteomic technology to identify differentially expressed proteins (DEPs) under varying nitrogen fertilizer levels. Additionally, it utilizes weighted gene co-expression network analysis (WGCNA) based on expression data of DEP-coding genes to explore the mechanism by which nitrogen promotes grain protein accumulation. The results indicate that high-nitrogen treatment leads to an increased grain protein content, wet gluten content, stability time, and energy area. In addition, the β-sheet content of the protein secondary structure increased, while the irregular curl content decreased. A total of 285 DEPs were identified under different nitrogen levels, with 172 upregulated proteins in grains under high-nitrogen treatment including storage proteins (8.14%) and proteins involved in nitrogen metabolism (8.72%), defense/stress (11.04%), regulation (26.16%), and transport (5.23%). This suggests that both storage proteins and certain metabolic proteins contribute to dough network formation. WGCNA revealed a strong correlation between the blue module and grain samples, and Gene Ontology analysis indicated that most genes were enriched in response to abscisic acid (ABA) in the “biological process” category. Furthermore, 18 core genes were identified, with most containing ABA response elements, light response elements, and motifs related to storage protein regulation in their promoter regions. Expression analysis of 10 genes and their predicted transcription factors during the grain-filling stage demonstrated higher expression levels under high-nitrogen conditions. This study provides valuable insights into the promotion of grain protein accumulation and dough quality by nitrogen fertilizer application.

This study aimed to investigate the effects of exogenous melatonin on grain yield and quality of brewing wheat grown under reduced nitrogen (N) fertilizer application. Field experiments were performed using two brewing wheat cultivars, Yunong 901 and Fanmai 8. Treatments included conventional N (225 kg∙ha⁻¹) and reduced N (150 kg∙ha⁻¹ and 120 kg∙ha⁻¹) levels, each with melatonin or water spray. The results demonstrated that reducing N fertilizer application led to decreased net photosynthetic rate, specific leaf N, and photosynthetic N use efficiency, while exogenous melatonin application improved corresponding photosynthetic parameters in all three N treatments. Reducing N decreased grain yield and grain endogenous hormone levels. Exogenous melatonin application increased grain yield under all N levels, with the highest increases in YN901 (10.61%) under MN and FM8 (10.27%) under LN. Melatonin partially restored grain hormone levels, particularly in the late filling stage under LN, maintaining higher filling activity. While reducing N decreased liquor volatile flavor compounds (alcohols, esters, N compounds), melatonin application significantly increased the total ester content and the relative levels of multiple volatile flavor compounds. Melatonin mitigated the adverse effects of N reduction, improving photosynthesis, grain yield, and liquor flavor quality. Comprehensively, reducing N to 150 kg∙ha⁻¹ combined with exogenous melatonin application improves grain yield, N efficiency, and liquor flavor quality.