Virus-like particles in the green alga Cylindrocapsa

Abstract

Icosahedral, virus-like particles (VLPs) have been studied in attached germlings of Cylindrocapsa geminella Wolle after the settling of zoospores produced by a heat-shock treatment. About 26 h after zoospore attachment, 3–10% of the resulting one-celled germlings contained a massive concentration of VLPs filling a region at the basal (i.e., attached) end of each cell. This includes the area normally occupied by the nucleus which is completely lysed by the time the VLPs are first observed. VLPs were found only in single-celled germlings, although the samples included multicellular germlings. Organelle degeneration occurs in the infected germlings and this apparently leads to cell lysis. Mature VLPs generally appear six-sided in section and have a maximum diameter of 200–230 nm. They possess a finely fibrillar core surrounded by a multilayered, membranous coat. The varied appearance of the virogenic stroma is discussed as well as putative stages in viral assembly. Cultures of Cylindrocapsa are being maintained from which VLP-infected germlings can be routinely obtained. The possibility that these cultures may be carrying a latent virus infection which can be induced by heat shock is discussed.