The rolB -transgenic Nicotiana tabacum plants exhibit upregulated ARF7 and ARF19 gene expression.

Agrobacterium rhizogenes root oncogenic locus B ( rolB ) is known to induce hairy roots along with triggering several physiological and morphological changes when present as a transgene. However, it is still unknown how this gene triggers these changes within the plant system. In this study, the effect of rolB in-planta , when present as a transgene, was assessed on the gene expression levels of auxin response factors ( ARF s)-transcription factors which are key players in auxin-mediated responses. The goal was to uncover Auxin/ ARF -driven transcriptional networks potentially active and working selectively, if any, in rolB transgenic background, which might potentially be associated with hairy root development. Hence, the approach involved establishing rolB -transgenic Nicotiana tabacum plants, selecting ARF s (Nt ARF s) for context-relevance using bioinformatics followed by gene expression profiling. It was observed that out of the chosen Nt ARF s, Nt ARF7 and Nt ARF19 exhibited a consistent pattern of gene upregulation across organ types. In order to understand the significance of these selective gene upregulation, ontology-based transcriptional network maps of the differentially and nondifferentially expressed ARF s were constructed, guided by co-expression databases. The network maps suggested that Nt ARF7 -Nt ARF19 might have major deterministic, underappreciated roles to play in root development in a rolB -transgenic background-as observed by higher number of "root-related" biological processes present as nodes compared to network maps for similarly constructed other non-differentially expressed ARF s. Based on the inferences drawn, it is hypothesized that rolB , when present as a transgene, might drive hairy root development by selective induction of Nt ARF7 and Nt ARF19 , suggesting a functional link between the two, leading to the specialized and characteristic rolB -associated traits.