Comparative transcriptome analysis of conventionally cultivated tobacco and tobacco grafted to eggplant

Tobacco (Nicotiana tabacum L.) grafted to eggplant (Solanum melongena L.) has been shown to limit nicotine content, however, the molecular mechanism of this graft combination remains unclear. In this study, we performed a genome-wide transcriptional analysis of Zhongyan-100 leaves, that were conventionally planted and grafted onto eggplant rootstocks, using high-throughput sequencing. The nicotine content in the leaves of the tobacco/eggplant grafting group was significantly decreased compared to the tobacco group. A total of 2389 differentially expressed genes (DEGs) were identified between the tobacco/eggplant group and tobacco group. Functional annotation revealed that many DEGs were involved in glutathione and linoleic acid metabolism, and phenylpropanoid, sesquiterpenoid, and triterpenoid biosynthesis. To explore whether nicotine level in tobacco changes after grafting, the expression of PMT, QPT, A622, and BBLa in the roots and stems was elucidated using quantitative PCR. This study found that the expression of these genes in the roots of the tobacco/eggplant group was significantly lower than that in the tobacco group. In addition, the expression of PMT, A622, and BBLa in tobacco stems of the tobacco/eggplant group was significantly higher than those in tobacco stems of the tobacco group and leaves of the tobacco/eggplant group. Our comprehensive analysis provides basic information on the genes and metabolic signaling pathways involved in Zhongyan-100/eggplant grafting. Additionally, this study found that the expression of nicotine-related genes changed during the grafting process; however, the specific molecular mechanisms underpinning this effect requires further exploration.