Transcriptomics combined with physiological analysis and metabolomics revealed the response of potato tuber formation to nitrogen

The absorption of the essential element nitrogen by plants affects various aspects of plant physiological activity, including gene expression, metabolite content and growth. However, the molecular mechanism underlying the potato tuberization response to nitrogen remains unclear. Potato plants were subjected to pot experiments under nitrogen deficiency, normal nitrogen levels and nitrogen sufficiency. A comprehensive analysis of the physiological responses, transcriptomic profiles, and metabolic pathways of potato stolons subjected to nitrogen stress was conducted. Transcriptomic analysis revealed 2756 differentially expressed genes (DEGs) associated with nitrogen stress. Metabolomic analysis identified a total of 600 differentially accumulated metabolites (DAMs). Further correlation analysis of the major DEGs and DAMs revealed that 9 key DEGs were associated with alpha-linolenic acid metabolism, 16 key DEGs with starch and sucrose metabolism, 7 key DEGs with nitrogen metabolism, and 16 key DEGs with ABC transporters. Nitrogen deficiency significantly increased the sucrose, GDP-glucose and L-glutamic acid levels and promoted stolon growth by increasing the expression of AMY (alpha-amylase), BE (1,4-alpha-glucan branching enzyme), SS (starch synthase), SPS (sucrose‒phosphate synthase) and AGPS (glucose‒1-phosphate adenylyltransferase). However, high nitrogen levels had the opposite effect. In addition, high nitrogen levels upregulated EG (endoglucanase), SUS (sucrose synthase) and GDH (glutamate dehydrogenase) and led to significant accumulation of 9-Hydroperoxy-10,12,15-octadecatrienoate (9(S)-HpOTrE), (13 S)-Hydroperoxyoctadeca-9,11,15-trienoate (13 (S)-HpOTrE) and L-glutamine, ultimately affecting the balance between plant growth and defense. Overall, our comprehensive study revealed the co-expressed genes and potential pathways related to potato tuber formation under different nitrogen conditions. These data provide a better understanding needed for improving potato tuber traits at the molecular and metabolic levels.