The biocontrol root endophyte Pseudomonas fluorescens PICF7 triggers systemic defense responses in above-ground olive tissues
Abstract: Pseudomonas fluorescens PICF7, a native olive root endophyte and effective biocontrol agent against Verticillium wilt of olive is able to trigger defense responses in root tissues of this woody plant. In order to elucidate whether systemic responses are also induced in above-ground organs, aerial tissues were collected at different time points after olive root bacterization with strain PICF7. A SSH cDNA library, enriched in olive up-regulated genes, was generated. Many of the induced genes were related to plant defense responses. ESTs were selected to carry out time-course qRT-PCR experiments aiming to: (i) validate their induction, and (ii) assess their expression pattern along time. Induction of genes coding for lipoxygenase 2 (LOX2), catalase (CAT), 1-aminocyclopropane-1-carboxylate oxidase (ACO) and phenylalanine ammonia-lyase (PAL) was confirmed for some of the analyzed time points. Different transcription factors were also up-regulated as previously reported for roots. Results confirmed that PICF7 colonization does not only trigger defense responses in root tissues but also can mount a range of systemic defense responses at distant organs.