Phenotypic And Transcriptomic Analysis Of Oat Seedlings Under Low Nitrogen Stress

Oat(A.nuda L.)can be used as food or forage,it has high nutritional value and also has a strong ability to resist adversity,which has led to its widespread cultivation worldwide.Currently,nitrogen deficiency is a significant factor limiting plant growth and production in agricultural production,especially during the seedling stage,when growth is rapid,physiological activity is more active,and environmental responses are more significant.This study used four naked oat varieties as experimental materials: As545(Hua Zao 2 Hao),As533(Meng Si Yan 7 Hao),As581(Nei You 6 Hao),As537(Ba You 1 Hao),measurements were taken under normal nitrogen and low nitrogen treatments for biomass-related parameters,including shoot and leaf fresh weight,root fresh weight,shoot and leaf dry weight,root dry weight,and root-to-shoot ratio.Parameters related to plant shoots,such as plant height,chlorophyll content,nitrogen content,leaf length,leaf width,and leaf area,were also determined.Additionally,data on root-related parameters,including total root length,root area,and primary root length,were collected.By comprehensively comparing various indexes,the nitrogen-sensitive and insensitive materials were screened out for transcriptome sequencing analysis,and the differentially expressed genes in stems,leaves and roots were analyzed,and the response of naked oats to low nitrogen was studied from the phenotypic and molecular levels,which provided a theoretical basis for further research on the mechanism of low nitrogen tolerance in naked oats.The main findings are as follows:1.Under low nitrogen conditions,four naked oat genotypes exhibited a decrease in fresh weight,plant height,chlorophyll content,nitrogen content,and leaf length.However,total root length,root area,and longest primary root length showed a significant increase.Among them,As581(Nei You 6 Hao)was the least sensitive to low nitrogen,while As533(Meng Si Yan 7 Hao)was the most sensitive.As533(Meng Si Yan 7 Hao)showed a significant decrease in leaf fresh weight,leaf dry weight,chlorophyll content,nitrogen content,leaf length,and leaf area,whereas root area and longest primary root length showed a significant increase.2.Transcriptome sequencing analysis was selected for the least sensitive As581(Nei You 6 Hao)to low nitrogen and the As533(Meng Si Yan 7 Hao)most sensitive to low nitrogen.Under different nitrogen concentrations,As533(Meng Si Yan 7 Hao)had a total of1,090 DEGs,with 514 upregulated and 576 downregulated DEGs.As581(Nei You 6 Hao)had a total of 466 DEGs,with 192 upregulated and 274 downregulated DEGs.Both genotypes exhibited a higher number of differentially expressed genes in the stems and leaves compared to the root system,and most of these DEGs were downregulated.The gene expression of two varieties was validated through RT-q PCR,which confirmed consistency with the transcriptome results.3.The DEGs in the root system and Straw of As533(Meng Si Yan 7 Hao)were mainly enriched in metabolic pathways such as valine,leucine,and isoleucine biosynthesis,ubiquinone and other terpenoid-quinone biosynthesis,phenylpropanoid biosynthesis,alanine metabolism,starch,and sucrose metabolism.The DEGs in the root system of As581(Nei You 6 Hao)Hao were primarily enriched in nitrogen metabolism,cysteine and methionine metabolism,pyruvate metabolism,and oxidative phosphorylation pathways.On the other hand,the DEGs in the stems and leaves of As581(Nei You 6 Hao)were only enriched in the photosynthesis pathway,and all of these DEGs were downregulated.