IMMUNOGOLD LOCALIZATION OF PATHOGENESIS-RELATED PROTEIN P14 IN TOMATO ROOT-CELLS INFECTED BY FUSARIUM-OXYSPORUM-F SP RADICIS-LYCOPERSICI

The accumulation of soluble pathogenesis-related (PR) P14 protein in tomato plants has only been reported in green tissue. An antiserum raised against purified PR P14 protein was used to study the spatial and temporal distribution of this protein in tomato root tissues infected by Fusarium oxysporum f. sp. radicis-lycopersici. Within healthy root tissue, PR P14 protein was found to be present in variable amount in cell walls, depending apparently on cell age and on the degree of tissue differentiation. Cell walls of infected tomato root tissues were markedly enriched in PR P14 protein. Although differences in the timing of PR P14 protein accumulation were observed between susceptible and resistant cultivars, the spatial distribution of the protein was similar in both interactions. Its predominant accumulation in host primary and secondary cell walls contrasted with its lack of association with the middle lamella. Deposition of PR P14 protein was also noticeable in intercellular spaces and within wall appositions. Its absence in the fungal wall provides support for a possible role in plant cell wall modification. This is contrary to other extracellular PR proteins such as chitinases and β-1,3-glucanases which are found associated with walls of invading fungal pathogens. © 1991 Academic Press Limited.