Journal of Plant Pathology & Microbiology

Abstract

Differential Accumulation of Defense-Related Transcripts by Inducers of Resistance in Arabidopsis

Martha Lydia Salgado-Siclán, Reyna Rojas-Martínez, Emma Zavaleta-Mejía, Daniel Ochoa-Martínez, Juan Burgueño-Ferreira, Beatriz Xoconostle-Cázares and Roberto Ruiz-Medrano

The plant defense response involves large changes in gene expression. Several inducers involved in such induction are known, including endogenous low-molecular weight compounds, as well as those derived from the pathogen such as membrane and cell wall fragments and secondary metabolites. Salicylic acid and hydrogen peroxide are well-known inducers of the response to pathogen attack, and synthetic compounds analogous to some of these resistance inducers show similar effects. Foliar fertilizers, besides the beneficial effect on plant growth, have been shown in some pathosystems to limit pathogen infection, particularly during phytoplasmoses. However, their modes of action in these cases are poorly understood. In order to gain insight into the mechanisms through which these complex mixtures may induce the defense response, the effect of one of this foliar fertilizers, NPKoligosaccharin
(known as KendalTM), on the accumulation of defense-related transcripts was analyzed in both mockinoculated and Turnip mosaic virus-infected Arabidopsis plants. Only a moderate induction was observed in the case of pathogenesis-related proteins (PR1) for NPK-oligosaccharin. On the other hand, viral infection plus this mixture induced PR1, MPK1 and TGA1 more effectively than the mixture alone. However, only peroxide treatment decreased virus levels; in contrast higher levels were observed in NPK-oligosaccharin treated plants. Confocal images of GFP-labeled TuMV support this observation. Our results suggest that treatment with foliar fertilizers may not be effective against certain pathogens.