ABA Is Required for Plant Acclimation to a Combination of Salt and Heat Stress.

Abiotic stresses such as drought, heat or salinity are a major cause of yield loss worldwide. Recent studies revealed that the acclimation of plants to a combination of different environmental stresses is unique and cannot be directly deduced from studying the response of plants to each of the different stresses applied individually. Here we report on the response of Arabidopsis thaliana to a combination of salt and heat stress using transcriptome analysis, physiological measurements and mutants deficient in abscisic acid, salicylic acid, jasmonic acid or ethylene signaling. Arabidopsis plants were found to be more susceptible to a combination of salt and heat stress compared to each of the different stresses applied individually. The stress combination resulted in a higher ratio of Na+/K+ in leaves and caused the enhanced expression of 699 transcripts unique to the stress combination. Interestingly, many of the transcripts that specifically accumulated in plants in response to the salt and heat stress combination were associated with the plant hormone abscisic acid. In accordance with this finding, mutants deficient in abscisic acid metabolism and signaling were found to be more susceptible to a combination of salt and heat stress than wild type plants. Our study highlights the important role abscisic acid plays in the acclimation of plants to a combination of two different abiotic stresses.

A fast and precise method to identify indolic glucosinolates and camalexin in plants by combining mass spectrometric and biological information.

In this manuscript, a fast and accurate identification and quantitation by mass spectrometry of indolic glucosinolates and camalexin involved in defense in Arabidopsis thaliana are described. Two elicitation systems, inoculation with Botrytis cinerea and treatment with AgNO(3), were used in Col-0 wild-type and mutant genotypes impaired in the biosynthesis of the selected metabolites. Identification of analytes was carried out by nontargeted LC/ESI-QTOF-MS profiling. Confirmation of indolic glucosinolates and camalexin was achieved by their absence in the cyp79B2/B3 and pad3 mutants as well as their respective fragmentation upon collision-induced dissociation. Camalexin accumulation was induced only after AgNO(3) treatment, whereas all indolic glucosinolates were constitutively present. Inoculation with Botrytis did not influence camalexin concentration but caused most aliphatic and indolic glucosinolates contents to decrease. Only the pen 3.1 mutant showed increased indolic glucosinolate levels after Botrytis or AgNO(3) treatments. In addition, profiles of secondary metabolite in nontreated Col-0 and mutant plants were analyzed by means of partial least squares coupled to discriminant analysis (PLS-DA), and differences in the basal levels of indolic glucosinolates and tryptophan between cyp79B2/B3 plants and the rest of genotypes, including Col-0, were found. This probably has to be taken into consideration when comparing stress responses of Col-0 and cyp79B2/B3. The use of mutants carrying alterations in biosynthetic pathways is proposed as a useful strategy to identify secondary metabolites.