Compensation Effect Of Nitrogen Deficiency In Early Maturity Rape(Brassica Napus L.)during Overwintering And Their Analyses Of Transcriptome And Metabolome

Nitrogen is the most important mineral elements for plant growth and development,plant shall adopt nitrogen deficiency compensation to maintain normal the period of duration and yield.Early-maturing cabbage type rape(Brassica napus L.)must be planting type for rape-rice-rice rotation in double-cropping rice areas in China.In order to elucidate the biological mechanism of nitrogen deficiency compensation in early-maturing rape,Ganyou105 with early-mature was used as the material in this dissertation,13 combined treatments of constant and double nitrogen fertilization were conducted every 5 days during the 30-day overwintering period,plant morphological and yield traits of rape were observed firstly to found the optimal treatment of nitrogen deficiency compensation effect,the soluble sugar,proline and nitrogen metabolism-related enzyme activities of rape under the treatments with significant differences were determined secondly to reveal the physiological base of nitrogen deficiency compensation effect,the leaves and roots of rape were analyzed with the method of transcriptome and metabolome to explore the molecular mechanisms of nitrogen deficiency compensation effect.The main results were as follow:1.The compensation effects of different nitrogen deficiency treatments on the plant morphology and yield traits of early-maturing rape were significantly different.The yield per plant of rape generally showed a trend of increasing firstly and then decreasing from overwintering stage I to VI under the constant and double nitrogen amount treatments after nitrogen deficiency.The compensation effects of silique length and seed number under different nitrogen deficiency treatments were not significant.The compensation effects of double nitrogen treatment T5 at overwintering stage II and constant nitrogen treatment T6 at overwintering stage III on leaf length and width were significantly higher than that of other treatments,that was,wintering stage III was the optimal period for nitrogen deficit compensation of rape.The compensation effects of yield trait between T6,T7 and T9 were significantly higher than that of other treatments and showed overcompensation effect,and there were also the significant differences among them.2.There differences of nitrogen-related enzyme activities in leaves of early-maturing rape under different nitrogen deficit treatments were significant.The significant compensation effects on glutamine synthetase activity and nitrate reductase activity of leaves in rape existed in nitrogen recovery after deficit,and its compensation effect was consistent with the compensation of yield traits.The constant nitrogen application in overwintering stage III could strengthen the high expression of measured enzyme activity.The activity of glutamate dehydrogenase of leaves in rape was the highest in T1,which was significantly higher than that in other treatments,but there was no significant difference among them,that was,nitrogen application at different intervals during the overwintering period had the same negative compensation effect on glutamate dehydrogenase.3.The differentially expressed genes under different nitrogen deficit treatments were enriched into different pathways.The GO enrichment results of transcriptome sequencing of roots and leaves showed that the differential metabolic genes in the overcompensation treatment group were enriched in cell components such as thylakoid and photosynthetic system,biological processes such as anion transport and cell carbohydrate metabolism,and molecular functions such as acid ammonia(or amide)ligase activity and anion transmembrane transporter activity.KEGG enrichment analysis showed that the differential metabolic genes in the overcompensation treatment group were enriched in pathways such as glyoxylic acid and dicarboxylic acid metabolism,pyruvate metabolism,carbon fixation in photosynthetic organisms,alanine,aspartic acid and glutamic acid metabolism,purine metabolism and ribosome biogenesis in eukaryotes.The differentially expressed genes in roots were enriched in pathways such as alanine,aspartic acid and glutamic acid metabolism,starch and sucrose metabolism,nitrogen metabolism and arginine biosynthesis.4.The differential metabolites under different nitrogen deficit treatments were enriched into different pathways.Through non-targeted metabolomics analysis,456 significant differential metabolites were obtained.KEGG analysis showed that the differential metabolites in the overcompensation treatment group were mostly enriched in alanine,aspartic acid and glutamic acid metabolism,pyrimidine metabolism,amino acid biosynthesis,nitrogen metabolism,glyoxylic acid and dicarboxylic acid metabolism,β-alanine metabolism,arginine biosynthesis and other pathways.Among them,alanine,aspartic acid and glutamic acid metabolism were the common pathways in the transcriptome and metabolome.