Abstract
BackgroundNitrogen application can effectively mitigate the damage to crop growth and yield caused by drought. However, the efficiency of heavy nitrogen application before drought (NBD) and heavy nitrogen application after drought (NAD) to regulate rice response to drought stress remains controversial. In this study, we profiled physiology, proteomics and metabolomics in rice variety Wufengyou 286 of two nitrogen management modes (NBD and NAD) to investigate their yield formation and the mechanism of nitrogen regulation for drought resistance.ResultsResults revealed that the yield of NBD and NAD decreased significantly when it was subjected to drought stress at the stage of young panicle differentiation, while the yield of NBD was 33.85 and 36.33% higher than that of NAD in 2017 and 2018, reaching significant levels. Under drought conditions, NBD increased chlorophyll content and net photosynthetic rate in leaves, significantly improved the activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase and catalase, and decreased malondialdehyde (MDA) content compared with NAD. NBD promoted nitrogen assimilation in leaves, which was characterized by increased activities of nitrate reductase (NR) and glutamine synthetase (GS). In addition, NBD significantly increased the contents of osmotic regulatory substances such as soluble sugar, soluble protein and free proline. Gene ontology and KEGG enrichment analysis of 234 differentially expressed proteins and 518 differential metabolites showed that different nitrogen management induced strong changes in photosynthesis pathway, energy metabolism pathway, nitrogen metabolism and oxidation-reduction pathways.ConclusionDifferent nitrogen management methods have significant differences in drought resistance of rice. These results suggest that heavy nitrogen application before drought may be an important pathway to improve the yield and stress resistance of rice, and provide a new ecological perspective on nitrogen regulation in rice.
Highlights
Nitrogen application can effectively mitigate the damage to crop growth and yield caused by drought
The results showed that the young panicle differentiation stage was the sensitive stage to water deficit in double cropping early rice
Metabolite profiles Firstly, Principal component analysis (PCA) was performed on the nitrogen application after drought (NAD) and nitrogen application before drought (NBD) samples, and the results showed that the model was credible in explaining the metabolic differences between the two groups (Fig. S2A); the PLS-DA model could better explain the differences between the NAD and NBD samples (Fig. S2B); the NAD and NBD samples had spectral separation on the OPLS-DA score plot (Fig. S2C), and the OPLS-DA model was tested with 200 response ranking tests, which showed that this model was not overfitting (Fig. S2D)
Summary
Nitrogen application can effectively mitigate the damage to crop growth and yield caused by drought. Oxygen as an important electron acceptor in leaves leads to the rapid accumulation of reactive oxygen species (ROS) such as singlet oxygen (O2−), superoxide (O2), hydroxyl (OH− 1) and hydrogen peroxide (H2O2) under adverse conditions, which has negative effects on antioxidant metabolism, resulting in cell peroxidation damage [4,5,6]. Antioxidant enzymes such as superoxide dismutase (SOD), peroxidase, catalase may play a central role in plant antioxidant metabolism under drought stress by regulating its gene expression and activity [7,8,9]. It leads to the accumulation of functional proteins, such as membrane proteins (aquaporins), osmotic regulatory molecules (including sucrose, proline and betaine), macromolecular protective factors (such as heat shock proteins, molecular chaperones, mRNA binding proteins) [13, 14], and overproduction of regulatory proteins (including transcription factors, protein kinases) [15, 16]
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