Comparative transcriptome analysis of melatonin or auxin treated-Arabidopsis

Objective: Melatonin and auxin are both tryptophan-derived indole molecules. Much attention has been given to proposed auxin-like activities of melatonin (regulating growth concentration-dependently). However, it still largely remains unclear whether melatonin and auxin regulate signalling pathways in a similar fashion. The purpose of this study is to directly compare the transcriptome response of Arabidopsis with melatonin or auxin. Method: mRNA profiles of 12-day old rosettes treated for a further of 3 days with +/- melatonin (5µM, 1005µM) or NAA(4.5µM) were generated by RNA-sequencing in triplicates (three independent biological experiments), using Illumina NextSeq 550 technology. Results: Comparative global transcriptome analysis conducted on Arabidopsis rosette treated with melatonin or NAA under exact same set of experimental conditions revealed differential number of genes and type of pathways. While auxin (4.5µM) regulated a large number of genes and elicited a diverse response, melatonin (100µM) showed a modest effect on transcriptome with only few genes significantly regulated whereas none regulated at approximately equimolar concentration with NAA (5µM) as compared to untreated solvent control (0.1% EtOH). Interestingly, the most prominent category of genes regulated by melatonin trended towards biotic stress defense pathways. Conclusions: These findings indicate that melatonin and auxin act quite differently toward signaling pathways in Arabidopsis. Melatonin has its own set of mechanisms to exert its functions, with strong inclination toward biotic defense pathways. mRNA profiles of +/- melatonin (5µM or 100µM) or NAA(4.5 µM)-treated Arabidopsis rosettes were generated by RNA-sequencing in triplicates (three independent biological experiments), using Illumina NextSeq 550.