Origin of a Meloidogyne incognita Surface Coat Antigen.

The surface coat (SC) of plant nematodes is thought to originate either from the living hypodermis or from secretory glands associated with the excretory system or nervous system. In this study, we investigated the origin of the SC of Meloidogyne incognita by immunolocalization with a monoclonal antibody raised against the surface coat of the preparasitic juveniles (J2). Under the electron microscope, strong labeling was found on the cuticular surface and in the rectal dilation of the J2, while labeling was absent in other parts of the nematode, including the hypodermis, excretory system, nervous system, and digestive system. Because the rectal glands are known to be the origin of the gelatinous egg matrix produced by adult females of Meloidogyne, we also examined sections of mature females from monoxenic cultures of Arabidopsis thaliana. Labeling of the female occurred in the rectal glands and in the gelatinous matrix exuded from the anus. At the ultrastructural level, gold particles were mainly deposited in multivesicular bodies that 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 the rectal gland cells and that the SC of the J2 shares common epitopes with the gelatinous egg matrix of mature females.