Integrated transcriptomic analysis reveals a transcriptional regulation network for the biosynthesis of lignin in Nicotiana tabacum in drought stress response

Lignin plays a crucial impact on the production of phenolic compounds in tobacco smoke, which have potential health implications associated with tobacco use. The meta-analysis of RNA-seq studies along with high-resolution expression analysis on Nicotiana tabacum clarified a conserved distinctive expression pattern of lignin gene network. According to the results, 67 DEGs associated with lignin biosynthesis network were identified of which 17 genes were introduced by meta-analysis. WGCNA showed 14 clusters for the meta-genes. Various TF families and a number of regulatory factors were identified as the most likely candidate genes associated with the lignin metabolic pathway. Eight major meta-genes were evaluated by using qRT-PCR in two tobacco genotypes with different lignin content under drought stress conditions. Genotype NC100 (high lignin content) and Burly (low lignin content) in response to PEG upregulated CAD 2, ATH12 and CAD 2, CCR , respectively. Despite the accumulation of lignin, the expression levels of CCoAOMT , F5H , COMT , and ODO1 were reduced in both genotypes. The study's exploration into the complex nature of these pathways and meta-analysis highlights the importance of adopting a more comprehensive approach to gene discovery. It suggests that conducting additional individual investigations is crucial for enhancing the reliability and comprehensiveness of gene identification within intricate metabolite pathways.