Time-course study of the accumulation of hydroxyproline-rich glycoproteins in root cells of susceptible and resistant tomato plants infected by Fusarium oxysporum f. sp. radicis-lycopersici.

The accumulation of hydroxyproline-rich glycoproteins (HRGPs) in cell walls of dicotyledonous plants is thought to be involved in the defense response to pathogens. An antiserum raised against deglycosylated HRGPs from melon was used for studying the subcellular localization of these glycoproteins in susceptible and resistant tomato (Lycopersicon esculentum Mill.) root tissues infected by Fusarium oxysporum f.sp. radicis-lycopersici. A time-course of HRGP accumulation revealed that these glycoproteins increased earlier and to a higher extent in resistant than in susceptible cultivars. In the compatible interaction, increase in HRGPs was largely correlated with pathogen invasion and appeared to occur as a result of wall damage. In the incompatible interaction, HRGPs accumulated in the walls of uninvaded cells, thus indicating a possible role in the protection against fungal penetration. The occurrence of substantial amounts of HRGPs in papillae, known to be physical barriers formed in response to infection, and in intercellular spaces provides additional support to the concept that such glycoproteins play an important role in disease resistance.