Abscisic acid-induced modulation of metabolic and redox control pathways in Arabidopsis thaliana.

Abscisic acid (ABA) has been implicated as a mediator in plant responses to various environmental stresses. To evaluate the transcriptional and metabolic events downstream of ABA perception, Arabidopsis thaliana seedlings were analyzed by transcript and metabolite profiling, and results were integrated, using the recently developed BioPathAt tool, in the context of the biochemical pathways affected by this treatment. Besides the up-regulation of pathways related to the biosynthesis of compatible solutes (raffinose family oligosaccharides and certain amino acids) as a response to ABA treatment, we also observed a down-regulation of numerous genes putatively localized to and possibly involved in the reorganization of cell walls, an association that had not been recognized previously. Metabolite profiling indicated that specific antioxidants, particularly alpha-tocopherol and L-ascorbic acid, were accumulated at higher levels in ABA-treated seedlings compared to appropriate controls. The transcription of genes involved in alpha-tocopherol biosynthesis were coordinately up-regulated and appeared to be integrated into a network of reactions controlling the levels of reactive oxygen species. Based upon the observed gene expression patterns, these redox control mechanisms might involve an ABA-mediated transition of mitochondrial respiration to the alternative, non-phosphorylating respiratory chain mode. The presented data herein provide indirect evidence for crosstalk between metabolic pathways and pathways regulating redox homeostasis as a response to ABA treatment, and allowed us to identify candidate genes for follow-up studies to dissect this interaction at the biochemical and molecular level. Our results also indicate an intricate relationship, at the transcriptional and possibly post-transcriptional levels, between ABA biosynthesis, the xanthophyll cycle, and ascorbic acid recycling.