Dissecting the transcriptional networks underlying the gibberellin response in Nicotiana tabacum

The present work examines global transcriptional and limited metabolic profiling to dissect the signalling pathways associated with gibberellin A 3 (GA 3 ) induced alterations in tobacco ( Nicotiana tabacum L.) under field conditions. Our microarray analysis revealed that GA 3 foliar application elicited 7 032 differentially expressed genes (DEGs) with 3 507 and 3 525 genes displaying up- and down-regulation, respectively. These DEGs broadly belong to diverse metabolic pathways: GA signalling and homeostasis, ethylene and auxin biosyntheses, saccharide metabolism, glycolysistricarboxylic acid cycle, terpenoid biosynthesis, shikimate-phenylpropanoid pathway, S-adenosyl methionine cycle, fatty acid biosynthesis, cell wall metabolism, oxidative stress, DNA repair, and stress responses. Transcription validation of representative DEGs was confirmed by real-time quantitative PCR. A relative enhancement in cellular acetyl-CoA pool corroborated with a concomitant increase and decrease in transcriptions as well as activities of histone acetyltransferases and histone deacetylases, respectively. Phytochemical analysis shows an enhanced content of total sugars, reducing sugars, total flavonoids, and phenolics with a concomitant decrease of the content of starch, chlorophylls a and b , and carotenoids. Gas chromatography with mass spectrometry analysis revealed the presence of 30 differential metabolites, mostly belonging to terpenoid biosynthesis pathway.