Regulation of photosynthesis, carbohydrate transport, and transcriptomic profiles in wheat by different fertilizers

BACKGROUND: In winter wheat cultivation, the rational application of organic-inorganic compound fertilizers increases grain weight and improves yield; however, the underlying mechanisms remain unclear. A 3-year field trial was conducted to investigate the effects of three fertilization regimes on photosynthesis, carbohydrate transport, and gene expression in wheat. The treatments included chemical fertilizer alone (CK), chemical fertilizer supplemented with composted pig manure (T1), and organic-inorganic compound fertilizer (T2). RESULTS: The T2 treatment resulted in significantly higher chlorophyll content and net photosynthetic rates in flag leaves compared to CK and T1. During the grain-filling stage, RuBP carboxylase activity in T2 increased significantly by 12.3% to 15.6%. Furthermore, the transport rate of non-structural carbohydrates (NSCs) in the stem sheaths of T2-treated wheat increased significantly by 23.84% and 20.38% compared to CK and T1, respectively. Correspondingly, NSC accumulation in the grains increased significantly by 15.80% and 18.94%, respectively. ADPG pyrophosphorylase activity in T2 was also significantly higher (by 72.4%) during the filling stage than in CK. Transcriptome analysis revealed that the highest number of differentially expressed genes (DEGs) associated with photosynthesis and carbon cycling were abundantly enriched in the flag leaves of T2. Specifically, in the T2 vs. T1 comparison, 1,420 up-regulated genes were primarily involved in photosynthesis and the carbon cycle, whereas in the T2 vs. CK comparison, 3,266 up-regulated genes were mainly associated with photosynthesis and cellular responses to light stimulation. Additionally, in the T2 treatment, several up-regulated genes involved in carbon fixation in photosynthetic organisms were simultaneously associated with the glyoxylate and dicarboxylate metabolism pathways. The most frequently identified DEGs in T2 belonged to the MYB-related, bZIP, ERF, and HB-other transcription factor (TF) families. CONCLUSION: The application of organic-inorganic compound fertilizers improves winter wheat yield by enhancing photosynthesis and the transport and accumulation of NSCs. Furthermore, it up-regulates the transcriptomic expression of genes related to photosynthesis and carbon cycling.