Assembly and accumulation sites of maize mosaic virus in its planthopper vector.

The morphology, assembly, and accumulation sites of rhabdovirus particles in Peregrinus maidis planthoppers infected with a Hawaiian isolate of maize mosaic virus (MMV) were studied. These particles were usually bullet-shaped, but were sometimes bacilliform, and averaged 234 and 247 nm, respectively, in length and 60 nm in width. They were found in most acini of the principal and accessory salivary glands and in brain, nerve ganglia, leg muscle, foregut, midgut, trachea, epidermis, and fat and connective tissues. In most tissues MMV particles accumulated mainly within intracytoplasmic, dilated cisternae that were connected to the perinuclear space. However, in the salivary glands virus particles accumulated mainly in intercellular and extracellular spaces and were found in secretion vesicles. MMV particles appeared to bud from three types of membranes: (i) inner, and rarely outer, nuclear membranes of cells in most tissues examined; (ii) intracytoplasmic membranes, e.g., endoplasmic reticulum in salivary glands; and (iii) plasma membranes of salivary gland cells and nerve axons. The plasma membrane has not been reported previously as a budding site for plant rhabdoviruses, although it is known as a major assembly site for animal rhabdoviruses.