The surface coat (SC) of plant nematodes is thought to originate either fro
m the living hypodermis or from secretory glands associated with the excret
ory system or nervous system. In this study, we investigated the origin of
the SC of Meloidogyne incognita by immunolocalization with a monoclonal ant
ibody raised against the surface coat of the preparasitic juveniles (J2). U
nder the electron microscope, strong labeling was found on the cuticular su
rface and in the rectal dilation of the J2, while labeling was absent in ot
her parts of the nematode, including the hypodermis, excretory system, nerv
ous system, and digestive system. Because the rectal glands are known to be
the origin of the gelatinous egg matrix produced by adult females of Meloi
dogyne, we also examined sections of mature females from monoxenic cultures
of Arabidopsis thaliana. Labeling of the female occurred in die rectal gla
nds and in the gelatinous matrix exuded from the anus. At the ultrastructur
al level, gold particles were mainly deposited in multivesicular bodies tha
t appeared to be associated with the Golgi bodies of the rectal glands. Our
results suggest that at least one component of the J2 SC originates from t
he rectal gland cells and that the SC of the J2 shares common epitopes with
the gelatinous egg matrix of mature females.