Elucidation of Response Mechanism of Potato to Nitrogen Stress by Physiological and Transcriptional Analyses

Background/Objectives: Nitrogen, as an indispensable macroelement for plants, is essential for tuber development. The objective of the present study was to ascertain the key factors underlying nitrogen regulation of potato tuber formation. Methods: The potato variety Kexin 37 was used as the material, and nitrogen deficiency, normal nitrogen level and excessive nitrogen level were employed as treatments, respectively. The response of potato tuber formation to nitrogen was systematically analyzed from the perspective of physiology and transcriptomics. Results: Nitrogen deficiency led to the thickening of the cell wall and plasma membrane, an increase in intercellular space and a decrease in mitochondria in the stolon. The plant height, chlorophyll content, dry matter quality and nitrogen accumulation were significantly reduced, and the number of tubers per plant, tuber weight per plant and commodity rate were significantly reduced. Excessive nitrogen application resulted in late maturity of plants and excessive formation of small potatoes. Transcriptome analysis revealed that differentially expressed genes related to nitrogen stress were mainly enriched in pathways associated with material transport, cell division and carbohydrate metabolism. In addition, there are a series of hub genes in response to nitrogen stress, including polyubiquitin-like, auxin response factor 7-like and protein RRP6-like 2. By constructing a co-expression network, transcription factors (TFs) such as C2H2, WRKY and ARF are involved in regulating tuber formation. Conclusions: The present study constitutes an investigation into the identification of hub genes and potential pathways associated with the formation of potato tubers under varying nitrogen conditions. It provides new insights for further study on enhancing nitrogen use efficiency in potato.