Characterization of the surface coat from infective juveniles of a root-knot nematode, Meloidogyne incognita.

Abstract

The nematode surface coat is defined as an extracuticular component on the outermost layer of the nematode body wall. Surface coat proteins of Meloidogyne incognita race 3 infective juveniles were characterized by electrophoresis and Western blotting of extracts from radioiodine and biotin-labeled nematodes. Extraction of labeled nematodes with cetyltrimethylammonium bromide yielded a principal protein band with a molecular weight larger than 200 KD and several faint bands of lower molecular weight ranging from 31 KD to 179 KD. Western blots of unlabeled proteins were probed with a panel of biotin-lectin conjugates, but only Concanavalin A bound to the principal band. Nematodes labeled with radioiodine and incubated in water for 20 hours released ¹²⁵I into the water, indicating that surface coat proteins may be loosely attached to the nematode. Antiserum to the principal protein reacted with the surface of live nematodes and with surface proteins previously separated by electrophoresis. Differential patterns of antibody labeling were obtained on Western blots of extracts from M. incognita race 1, 2, and 3, Meloidogyne hapla race 2, and Meloidogyne arenaria race B. One biological role of the surface coat may be to act as the receptor site for attachment of the nematode bacterial parasite, Pasteuria penetrans. This possibility is suggested because antiserum raised against surface coat proteins of Meloidogyne incognita race 3 reduced bacterial attachment.