Transcriptome analysis of nitrate enhanced tobacco resistance to aphid infestation

Tobacco is an economic crop that primarily relies on nitrate (NO₃^-) as its nitrogen source, and tobacco aphid is one of the significant pests that harm its growth. However, the impact of NO₃^- supply on the resistance of tobacco to aphids remains unclear. Present study investigated the effects of different NO₃^- concentrations supply on the reproductive capacity of tobacco aphids, impact of aphid infestation on tobacco growth, secondary metabolic and transcription changes. Physiological experiments were performed to verity the transcription analysis. The results indicated that aphids preferred tobacco treated with higher concentration of nitrate, showing greater reproductive capacity under high nitrate supply. From the results of transcriptome analysis, it can be seen that the gene expression of the shoot changed significantly after aphid and NO₃^- treatment. GO analysis showed that the pathways associated with cell wall biosynthesis were enriched in different groups. At the same time, RNA-seq analysis revealed several genes related to the pathway of aphid damage in tobacco, as well as some transcription factors associated with insect resistance. Inoculating tobacco with aphids under different NO₃^- concentration increased the levels of soluble sugars, free amino acids, jasmonic acid, and salicylic acid in shoot of tobacco. Additionally, it was observed that the cell wall development of leaves from low NO₃^- supply was incomplete, and the cell wall from high NO₃^- supply concentration is notably thicker. The lignin content was lower under lower NO₃^- supply, regardless of aphid inoculation. The trends of transcription levels in genes related to cell wall and lignin biosynthesis were consistent with the lignin contents. Collectively, our findings not only shed light on the physiological and biochemical responses of tobacco plants to NO₃^- treatment, but also offer novel perspectives for optimizing tobacco cultivation practices and enhancing insect resistance.