Anti-idiotypic antibodies can mimic the ability ofPhytophthora infestansto induce the accumulation of transcripts associated with defence responses in potato

Abstract

The initial infection process involving adhesion/recognition events between plants and fungal pathogens is essential for the establishment of pathogenesis. The basis of the specificity betweenPhytophthora infestansand potato is not yet known. It could lie in the recognition between extracellular matrix and plasma membrane components of the penetrating structures of the fungus and host cells during the earliest stages of infection processes. We have used polyclonal antibodies (AZandAC) obtained after immunizing rabbits with either 107zoospores (Z) or germinating cysts (C) ofP. infestansto detect putative fungal components located on the surface of invasive structures.AZrecognized several bands, whileACrecognized three polypeptides of approximately 87, 73 and 45 kDa in western blots. Zoospore suspensions preincubated either withAZorACwere unable to infect potato leaves. Since it was already known that some anti-idiotypic (anti-IT)antibodies may resemble the antigen, thus mimicking its structure,anti-ITantibodies (a-AZanda-AC)were generated in mice and used as inducers on potato tuber discs. In northern blotsa-AZtreatments increased 1.5-fold the glyceraldehyde-3-P dehydrogenase (GAPDH) and 1.8-fold the phenylalanine ammonia-lyase (PAL) transcript levels, while an increase of 1.8 and 1.7-fold for GAPDH and PAL, respectively, was observed when the inducer wasa-AC.Both PAL and GAPDH transcript levels have previously been shown to be modulated by fungal and elicitor treatments. These results show that the anti-idiotypic antibodies are able to mimic the pathogen components, leading to the accumulation of transcripts related to defence responses in potato–P. infestansinteraction.