Combined proteomics, metabolomics and physiological analyses of rice growth and grain yield with heavy nitrogen application before and after drought.

BACKGROUND: Nitrogen 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. RESULTS: Results 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. CONCLUSION: Different 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.

iTRAQ-based quantitative proteomic and physiological analysis of the response to N deficiency and the compensation effect in rice.

BACKGROUND: The crop growth compensation effect is a naturally biological phenomenon, and nitrogen (N) is essential for crop growth and development, especially for yield formation. Little is known about the molecular mechanism of N deficiency and N compensation in rice. Thus, the N-sensitive stage of rice was selected to study N deficiency at the tillering stage and N compensation at the young panicle differentiation stage. In this study, a proteome analysis was performed to analyze leaf differentially expressed proteins (DEPs), and to investigate the leaf physiological characteristics and yield under N deficiency and after N compensation. RESULTS: The yield per plant presented an equivalent compensatory effect. The net photosynthetic rate, optimal/maximal quantum yield of photosystem II (Fv/Fm), soil and plant analyzer development (SPAD) value, and glutamic pyruvic transaminase (GPT) activity of T1 (N deficiency at the tillering stage, and N compensation at the young panicle differentiation stage) were lower than those of CK (N at different stages of growth by constant distribution) under N deficiency. However, after N compensation, the net photosynthetic rate, Fv/Fm, SPAD value and GPT activity were increased. Using an iTRAQ-based quantitative approach, a total of 1665 credible proteins were identified in the three 4-plex iTRAQ experiments. Bioinformatics analysis indicated that DEPs were enriched in photosynthesis, photosynthesis-antenna proteins, carbon metabolism and carbon fixation in the photosynthetic organism pathways. Moreover, the photosynthesis-responsive proteins of chlorophyll a-b binding protein, ribulose bisphosphate carboxylase small chain and phosphoglycerate kinase were significantly downregulated under N deficiency. After N compensation, chlorophyll a-b binding protein, NADH dehydrogenase subunit 5, NADH dehydrogenase subunit 7, and peroxidase proteins were significantly upregulated in rice leaves. CONCLUSION: Through physiological and quantitative proteomic analysis, we concluded that a variety of metabolic pathway changes was induced by N deficiency and N compensation. GO and KEGG enrichment analysis revealed that DEPs were significantly associated with photosynthesis pathway-, energy metabolism pathway- and stress resistance-related proteins. The DEPs play an important role in the regulation of N deficiency and the compensation effect in rice.

Comprehensive metabolomic and proteomic analysis in biochemical metabolic pathways of rice spikes under drought and submergence stress.

Drought and submergence are the main adverse factors affecting plant growth and yield formation in parts of China, especially in the Yangtze River region. In this study, T1 (drought duration: 10 d), T2 (submergence duration: 8 d) and CK (control) treatments were applied. This work aimed to study the changes in metabolic pathways of rice under drought and submergence stress during the panicle differentiation stage. The identification and analysis of differential metabolites and differentially expressed proteins functions indicate that drought and submergence mainly promoted the energy metabolism pathway, carbon fixation in photosynthetic organism pathway, carbohydrate metabolic process, and reactive oxygen species (ROS) metabolic process functions. Under drought stress, the inhibition of photosynthetic rate is mainly through stomatal conductance restriction, and flavonoid pathway regulates the metabolic process of ROS. Under submergence stress, the electron transfer chain was destroyed to inhibit the photosynthetic rate, and the antioxidant system was activated to regulate the metabolism of ROS. The changes in related enzymes or proteins in metabolic regulatory networks are analyzed, which will be conducive to understanding the response mechanism of rice drought and submergence more deeply and provide a scientific basis for rice drought and submergence prevention and mitigation, and the breeding of drought- and submergence-resistant varieties.

Comprehensive metabolomic, proteomic and physiological analyses of grain yield reduction in rice under abrupt drought-flood alternation stress.

Abrupt drought-flood alternation (T1) is a meteorological disaster that frequently occurs during summer in southern China and the Yangtze river basin, often causing a significant loss of rice production. In this study, the response mechanism of yield decline under abrupt drought-flood alternation stress at the panicle differentiation stage was analyzed by looking at the metabolome, proteome as well as yield and physiological and biochemical indexes. The results showed that drought and flood stress caused a decrease in the yield of rice at the panicle differentiation stage, and abrupt drought-flood alternation stress created a synergistic effect for the reduction of yield. The main reason for the decrease of yield per plant under abrupt drought-flood alternation was the decrease of seed setting rate. Compared with CK0 (no drought and no flood), the net photosynthetic rate and soluble sugar content of T1 decreased significantly and its hydrogen peroxidase, superoxide dismutase, peroxidase activity increased significantly. The identified differential metabolites and differentially expressed proteins indicated that photosynthesis metabolism, energy metabolism pathway and reactive oxygen species response have changed strongly under abrupt drought-flood alteration stress, which are factors that leads to the rice grain yield reduction.

Synthesis of novel chiral tridentate Schiff-base ligands and their applications in catalytic asymmetric Henry reaction.

A series of chiral tridentate Schiff-bases were prepared and used as ligands in the catalytic asymmetric Henry reaction. Under the optimal conditions, a variety of arylaldehydes were smoothly converted into corresponding adducts with high yields (up to 98%) and excellent enantioselectivities (up to 97% ee).