Hydroxyproline-rich proteins and peroxidases in tomato roots infested by root-knot nematode

Abstract

Hydroxyproline-rich glycoproteins (HRGP) have long been known to be associated with the cell wall of all higher plant tissues (Lamport, 1965). The low level of these proteins is strikingly increased in response to wounding (Chrispeels, 1969; Stuart and Warner, 1980), fungi infection (Hammerschmidt and Kuc', 1982; Touze and Esquerre-Tugaye, 1982) and nematode infestation (Giebel and Stobiecka, 1974; Zacheo et al., 1977). It is suggested that small glycoproteins may playa role in a general defense mechanism of plants against biological stress (Touze and Esquerre-Tugaye, 1982). This is of interest as such glycoproteins were associated with the resistant response of plant to pathogens. The role that HRGPs play in defence is not known although there are suggestions that they act as growth regulating materials. Some authors (Whitmore, 1978) have suggested that IIRGPs may act as matrices for lignification in a lignin protein complex catalyzed by peroxidase. Ridge and Osborne (1970) proposed that peroxidase could be one of the group of IIRGPs in cell walls, the level of which determine wall extensibility and cell growth. This study was carried out to determine whether the increase of hydroxyproline in plants infested by Meloidogyne incognita is associated with parallel changes in peroxydase activity.