Integrated transcriptomic data reveal a regulatory network for the lignin biosynthesis in Nicotiana tabacum upon drought stress

Lignin plays a crucial role in the production of phenolic compounds in tobacco smoke that have potential health effects associated with tobacco use. A meta-analysis of RNA-seq research and analysis of Nicotiana tabacumrevealed distinctive expression patterns of the lignin biosynthetic network. Through a meta-analysis of RNA-seq data on Nicotiana tabacum under drought stress, we identified 67 differentially expressed genes (DEGs) associated with lignin biosynthesis. Notably, 17 of these DEGs were detected only through meta-analysis, and not in individual investigations. WGCNA showed 14 clusters for the meta-genes. Several TF families and regulatory factors were identified as the most likely candidate genes related to the lignin metabolic pathway. Quantitative RT-PCR analysis of eight major meta-genes in two tobacco genotypes with contrasting lignin content (NC100 – high lignin content; Burley, low lignin content) under PEG-induced drought stress showed genotype-specific responses. CAD2 and ATH12 were upregulated in NC100, while CAD2 and CCR were upregulated in Burly. Interestingly, despite overall lignin accumulation, expression levels of CCoAOMT, F5H, COMT, and ODO1 were reduced in both genotypes.Our findings highlight the complex regulation of lignin biosynthesis under drought stress and the importance of genotype-specific responses. This study demonstrates the power of meta-analysis in identifying DEGs not detected in individual investigations, enhancing our understanding of lignin metabolism in tobacco under drought conditions. The observed genotype-specific differences underscore the need for tailored approaches in studying lignin biosynthesis in various tobaccocultivars under stress.