19 páginas, 6 figuras, 2 tablas.Menadione sodium bisulphite (MSB) is a water-soluble derivative of vitamin K3, or menadione, and has been previously demonstrated to function as a plant defence activator against several pathogens in several plant species. However, there are no reports of the role of this vitamin in the induction of resistance in the plant model Arabidopsis thaliana. In the current study, we demonstrate that MSB induces resistance by priming in Arabidopsis against the virulent strain Pseudomonas syringae pv. tomato DC3000 (Pto) without inducing necrosis or visible damage. Changes in gene expression in response to 0.2 mm MSB were analysed in Arabidopsis at 3, 6 and 24 h post-treatment using microarray technology. In general, the treatment with MSB does not correlate with other publicly available data, thus MSB produces a unique molecular footprint. We observed 158 differentially regulated genes among all the possible trends. More up-regulated genes are included in categories such as 'response to stress' than the background, and the behaviour of these genes in different treatments confirms their role in response to biotic and abiotic stress. In addition, there is an over-representation of the G-box in their promoters. Some interesting functions are represented among the individual up-regulated genes, such as glutathione S-transferases, transcription factors (including putative regulators of the G-box) and cytochrome P450s. This work provides a wide insight into the molecular cues underlying the effect of MSB as a plant resistance inducer.This work was partially funded by an INVESCAN, S.L. grant (No.OTT2001438) to the CSIC and by a BIO2006-02168 grant of MICINN to PT. The microarrays were funded in part by the “Genome España” Foundation. MER was supported by a research contract (ID-TF-06/002) from the Consejería de Industria, Comercio y Nuevas Tecnologías (Gobierno de Canarias). The authors thank CajaCanarias for their research support. We also thank Lorena Perales for her help in performing the bacterial growth curves, Dr. Héctor Cabrera for his useful advice on writing the manuscript, the English translation service of the Universidad Politécnica de Valencia and Mrs. Pauline Agnew whose endeavoured to edit the English translation of this paper.Peer reviewe
