Identification of indole-3-carboxylic acid as mediator of priming against Plectosphaerella cucumerina

• Published in: Plant physiology and biochemistry 2012-12, Vol.61, p.169-179
• Main Authors: Gamir, J., Pastor, V., Cerezo, M., Flors, V.
• Format: Article
• Language: English
• Subjects: Aminobutyrates - pharmacology; Arabidopsis; Arabidopsis - drug effects; Arabidopsis - metabolism; Arabidopsis - microbiology; BABA; Biological and medical sciences; callose; cell walls; Chromatography, Liquid - methods; Disease Resistance; Fundamental and applied biological sciences. Psychology; Fungi; Glucans - metabolism; indole acetic acid; Indole-3-carboxylic acid; Indoles - metabolism; liquid chromatography; Mass Spectrometry - methods; metabolites; P. cucmerina; pathogens; Plant Diseases - microbiology; Plant Immunity; Plant physiology and development; Precursor ion scanning; Priming; Signal Transduction
• ISSN: 0981-9428; 1873-2690
• DOI: 10.1016/j.plaphy.2012.10.004

Plant resistance against the necrotrophic pathogen Plectosphaerella cucumerina is mediated by a combination of several hormonal-controlled signalling pathways. The priming agent β-aminobutyric acid (BABA) is able to induce effective resistance against this pathogen by stimulating callose-rich cell wall depositions. In the present research it is demonstrated that BABA-Induced Resistance (BABA-IR) against P. cucumerina in Arabidopsis has additional components such as the induction of defences mediated by indolic derivatives. Chromatographic approach for the detection and characterization of metabolites enhanced by BABA compared with water-treated plants only when the challenge is present has been developed. The metabolites matching this criteria are considered to be primed by BABA. The analytic procedure is based on the combination of liquid chromatography (LC) with a triple quadrupole (TQD) detector in a precursor ion scanning mode. Using this analytical system a signal in negative electro-spray mode of 160 m/z is primed by BABA in infected plants. A subsequent exact mass analysis in a quadrupole time-of-flight mass spectrometer demonstrated that this ion was the indole-derivative metabolite indole-3-carboxylic acid (I3CA). The identity of indole-3-carboxilic acid was definitively confirmed by comparing its retention time and fragmentation spectra with a commercial standard. Quantification of I3CA in primed plants showed that this indolic metabolite is specifically primed by BABA upon P. cucumerina infection, while other indolic compounds such as IAA and camalexin are not. Taking together these observations with the known role of callose in priming against this pathogen, suggests that priming is not a single mechanism but rather a multicomponent defence. ► Using the Precursor Ion Scanning in infected plants we found the precursor ion 160 m/z. ► The ion 160.0409 m/z was identified as I3CA using a TOF analyser. ► BABA primes for I3CA accumulation. It may participate in enhancing plant's resistance.