Metabolic and transcriptional profiling of Arabidopsis thaliana fou2 mutant
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Glucosinolates (GSL) are important secondary metabolites found mainly in the Brassicaceae plant family. Jasmonic acid (JA) and its derivatives (JAs) are biologically active molecules playing important role in cell signaling. They regulate plant development and responses to awide range of stress stimuli. It has been demonstrated that JAs may be involved in the regulation of GSL biosynthesis pathway. The rising concentrations of JA upon wounding increase the total GSL content in plant tissue. The mechanism responsible for this regulation is, however, not fully understood. The fatty acid oxygenation up-regulated 2 (fou2) mutant has been found to have increased levels of JA as a result of a mutation in the two pore channel 1 (TPC1) gene. The mutant haselevated levels of two key enzymes involved in JA biosynthesis and this result in an increased capacity to accumulate JAs. A pilot study revealed that several GSL accumulate to higher levels in the fou2 mutant compared to wt control plants. However, the fou2 phenotype onlybecomes visible after a natural transition period, where the activity of the JA pathwaybecomes naturally increased. Metabolic profiling of fou2 plants before and after the transition revealed that the GSL profile of young mutant plants is similar to the profile of wild type (wt) plants. Two additional mutants were investigated in order to find out whether the changed GSLlevels, observed in older fou2 mutant plants, could be directly related to the changed properties of the mutated TPC1, or indirectly result from the high JA profile of the mutant. GSL profiles of TPC1 over expressing mutant and tpc1 knockout mutant were compared with the GSL profile of fou2. Quantitative changes in TPC1 protein levels were found to have little effect on the GSL levels of the investigated mutants. Further, the GSL profile of a double mutant, carrying fou2 and aos alleles (fou2xaos) wasinvestigated. This double mutant lacks the key JA enzyme, AOS, and is therefore deficient in JA biosynthesis. The indole GSL levels of the double mutant did not resemble the levels of fou2, this indicates an important function of JA signaling in regulation of tryptophan derived GSL synthesis. The levels of some aliphatic GSLs, however, were changed in the double mutant in comparison to aos and wt controls. This finding points towards a possible direct link between the TPC1 activity and the accumulation of some GSLs types. Further analysis, employing transcriptional profiling of fou2xaos double mutant, will hopefully bring new insights into the mechanism(s) dependent on TPC1 activity and involved in the regulation of aliphatic GSL pathway.