Basic Studies On The Morphology,physiology And Molecular Biology Of Peanut Response To Low Nitrogen Stress

With the increase of nitrogen fertilizer application in the world,environmental damage and the decrease of nitrogen use efficiency make screening peanut varieties with high nitrogen efficiency and improving peanut nitrogen use-efficiency become a hot topic in peanut research.However,the response mechanism of different genotypes of peanut to nitrogen levels was not clear.Therefore,in order to screen peanut varieties with different nitrogen efficiency and analyze the difference of peanut morphological,physiological and molecular response to nitrogen deficiency,24 peanut genotypes from different institutions and units were used for hydroponics at different batches in green house.Taking nitrogen sufficiency as control,the changes of shoot morphology and root morphology of peanut seedlings with different genotypes under nitrogen deficiency were studied,as well as physiological indexes such as nitrogen content,enzyme activities related to nitrogen metabolism,carboxylase activity of Ribulose-1,5-diphosphate/oxygenase(Rubisco),peroxidase(POD)activity and photosynthetic characteristics.In addition,the bio-information and expression levels of Rubisco small subunit(RBCS)and POD family genes were identified.The morphological,physiological and molecular responses of peanut under different nitrogen levels were analyzed.And the main test results are as follows:Under nitrogen deficiency,there were differences in shoot morphological responses of peanut seedlings with different genotypes.Among the 24 different genotypes of peanut in the experiment,nitrogentolerant peanut varieties,such as Sanhua2 and Yuanza14,effectively improved nitrogen use-efficiency and increase nitrogen content of seedlings by increasing the enzyme activities of GS,GOGAT and GDH under the condition of short-term nitrogen deficiency,to effectively adapt the adverse effects of lack of stress on growth and development.And reduce the inhibitory effect of nitrogen deficiency on aboveground dry weight,stem growth,and root development.There are 8 members of peanut RBCS family gene,and there are a large number of cis-acting elements related to light response at 1500 bp of their promoters.The gene expression profile of RBCSs was changed significantly by nitrogen deficiency.Under the condition of nitrogen deficiency,the gene expressions of Ah RBCS1/5 and Ah RBCS2/6 were significantly up-regulated,while Ah RBCS3/4/7/8 were significantly down-regulated.The electron transfer rate and carboxylation activity of Rubisco in peanut seedlings were reduced,and the carbon assimilation ability of leaves was weakened,which resulted in the decreased photosynthetic ability of leaves,and thus inhibited the shoot growth of peanut seedlings.The nitrogen tolerant peanut varieties,Pukehua 18 and Luohua 4087,grew stronger at seedling stage and had stronger adaptability to low nitrogen stress than non-nitrogen tolerant varieties.A total of 170 POD family genes were identified through bioinformatics analysis,and the tandem duplication events of genes are an important way to expand the POD family members of peanut.By correlation analysis,POD enzyme activity was negatively correlated with seedling main root elongation.There was significant correlation between POD family genes and root morphogenesis of peanut seedlings.For example,Ah POD020/024 was positively correlated with the main root length of peanut seedlings,while Ah POD011,Ah POD039 and Ah POD046 were negatively correlated with the main root length of peanut seedlings.The number of first-order lateral roots was positively correlated with Ah POD009,Ah POD020/024 and Ah POD057.Nitrogen tolerant peanut seedlings,Sanhua2 and Yuanza14,effectively improved the ability to adapt to nitrogen deficiency by changing the POD family gene expression profile.Nitrogen tolerant peanut seedlings,Sanhua 2 and Yuanza 14,were improved their ability to adapt to nitrogen deficiency by changing expression profile of POD.In conclusion,peanut genotypes have different responses to low nitrogen stress.By analyzing the shoot and root morphology,nitrogen metabolism,Rubisco and POD enzyme activities,and molecular changes of different genotypes of peanuts under nitrogen deficiency,four nitrogen-tolerant peanut varieties,Pukehua 18,Sanhua 2,Yuanza 14 and Luohua 4087 were identified.The research provides a new idea and way for screening peanut varieties with high nitrogen efficiency and improving the efficiency of nitrogen fertilizer use in peanut.