Abstract In tobacco production, the nicotine content of tobacco leaves in China is high to varying degrees, resulting in inconsistent chemical composition of tobacco leaves, which affects the industrial availability of tobacco leaves and causes a large backlog of tobacco leaves in stock. Therefore, effective reduction of nicotine content in flue-cured tobacco leaves has become an important issue in tobacco production. Based on the fact that mechanical injury such as topping can stimulate nicotine synthesis in tobacco plants by activating the jasmonic acid (JA) signal, this study explored the possible pathway of salicylic acid (SA) antagonizing JA signal to regulate nicotine synthesis in tobacco plants by using the antagonistic effect of SA and JA in signal transduction. Using Nicotiana tabacum cv. 'Yunyan 87' as the experimental material, the tobacco plants were subjected to mechanical damage treatments, such as topping and leaf picking, when they were growing to full flowering stage. The effects of SA on the expression of nicotine biosynthesis-related genes and the content of total nitrogen and nicotine in the tobacco plants were analyzed, and the transcriptomic analysis of the tobacco roots treated with JA, SA and JA+SA was performed. The results showed that multiple mechanical injuries further induced the expression of nicotine biosynthesis genes and the conversion of nitrogen to nicotine biosynthesis pathway. In contrast, SA could antagonize JA signaling, inhibit the expression of nicotine biosynthesis genes, hinder the conversion of nitrogen to nicotine biosynthesis pathway, and reduce the nicotine content in tobacco plants. The transcriptomics-based co-expression network analysis showed that 14 transcription factors belonging to the bHLH, AP2-EREBP and WRKY families, respectively, were not only significantly induced by SA, but also their expression patterns were negatively correlated with nicotine biosynthesis genes. In addition, promoter cis-element analysis revealed that the promoters of nicotine biosynthesis-related genes were widely distributed with cis-acting elements that could be recognized by bHLH, AP2/ERF and WRKY, which provided the possibility that bHLH, AP2-EREBP and WRKY transcription factors could repress the transcription of target genes by binding to the promoters. This study provides a reference for effective regulation of nicotine synthesis and improvement of tobacco leaf quality.
LI Han,CAI Kai,GAO Wei-Chang, et al. Study on the Regulation of Nicotine Synthesis Based on the Antagonism of Jasmonic Acid and Salicylic Acid[J]. 农业生物技术学报, 2023, 31(8): 1595-1609.
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