Abstract
Nitrate (NO3−) and ammonium (NH4+) are the main inorganic nitrogen (N) sources absorbed by oilseed rape, a plant that exhibits genotypic differences in N efficiency. In our previous study, the biomass, N accumulation, and root architecture of two oilseed rape cultivars, Xiangyou 15 (high N efficiency, denoted “15”) and 814 (low N efficiency, denoted “814”), were inhibited under NH4+ nutrition, though both cultivars grew normally under NO3− nutrition. To gain insight into the underlying molecular mechanisms, transcriptomic changes were investigated in the roots of 15 and 814 plants subjected to nitrogen-free (control, CK), NO3− (NT), and NH4+ (AT) treatments at the seedling stage. A total of 14,355 differentially expressed genes (DEGs) were identified. Among the enriched Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway categories of these DEGs, carbohydrate metabolism, lipid metabolism, protein metabolism, and cell wall biogenesis were inhibited by AT treatment. Interestingly, DEGs such as N transporters, genes involved in N assimilation and CESA genes related to cellulose synthase were also mostly downregulated in the AT treatment group. This downregulation of genes related to crucial metabolic pathways resulted in inhibition of oilseed rape growth after AT treatment.
Highlights
Nitrogen (N) is an indispensable macronutrient for plant growth and development that serves as a constituent of many crucial macromolecules, including proteins, enzymes, and nucleic acids, and acts as a signal to regulate many biological processes from metabolism to resource allocation, growth and development
The results indicate that carbohydrate metabolism, lipid metabolism and protein metabolism were inhibited in the AT treatment group, which led to decreased growth
In the Gene Ontology (GO) term analysis performed in this study, we found that the numbers of differentially expressed genes (DEGs) involved in primary cell wall biogenesis (CWB) (GO: 0009833) differed between the comparison groups (Table 2)
Summary
Nitrogen (N) is an indispensable macronutrient for plant growth and development that serves as a constituent of many crucial macromolecules, including proteins, enzymes, and nucleic acids, and acts as a signal to regulate many biological processes from metabolism to resource allocation, growth and development. Nitrate (NO3 − ) and ammonium (NH4 + ) are the main N forms absorbed and utilized by plants, accounting for 70% of anion and cation absorption [1]. The mechanisms used by plants to absorb and utilize NO3 − and NH4 + differ, and NO3 − and NH4 + can affect plant growth and physiological processes, such as dry matter accumulation, root morphology, photosynthesis, and N assimilation. Researchers have carried out studies on the effects of different N forms on the growth and physiology of plants, but the conclusions of these studies vary due to differences among plant species and genotypes.
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