Viruses Genomes - ECTOCARPUS SILICULOSUS VIRUS

Ectocarpus siliculosus Virus (EsV-1) is the founding member of a new genus of marine viruses, the phaeoviruses. EsV-1 is endemic in all populations of Ectocarpus siliculosus. EsV-1 has a large circular double-stranded DNA genome of about 320 kilobase pairs.

Ectocarpus siliculosus is a brown alga that takes the form of an uniseriate (arranged in one row) , branched filament which may appear as light brown tangled tufts. It is common year round and is found in pools at high tide levels, on all coasts of temperate climate zones. It is frequently free floating but it may be attached to rocks or other algae. It is used to make soap, and to fix the colors and emulsion of photographic films.

Studies under controlled laboratory conditions show that EsV-1 and other phaeoviruses only infect the wall-less, free-swimming spores or gametes of the algal host. Strong evidence indicates that the viral DNA is incorporated into the genome of the infected cell and transmitted to all cells of the developing organism. Free virus particles are infective for a few days and can invade swimming gametes or spores of healthy plants, but cannot infect somatic Ectocarpus cells which are protected by their solid cell wall. Virus release is triggered by environmental cues such as changes of culture medium or temperature.

Investigation of EsV-1 is expected to be rewarding for several reasons. One is that EsV-1 could serve as a probe to investigate the molecular biology of its host. For example, the cell-specific replication of viral DNA implies that cells in reproductive organs express factors essential for viral gene expression and provide important insights into the developmental program of reproduction in marine algae. It can also be expected that EsV-1 will be useful in biotechnology. Integrated latent viral DNA carrying a foreign gene should produce high quantities of the product of that gene. This could be technically exploited because latently infected algae remain somatically unaffected and can be mass-cultivated at low cost. There are also ecological reasons for further studies on EsV-1 since this virus is widely distributed within all Ectocarpus populations worldwide. 50 to 100% of all specimens within an Ectocarpus population usually carry the latent viral genome. To explain this high degree of infection, it has been proposed that EsV-1 evolved to reduce sexual recombination in favour of mitotic reproduction in its algal host but this possibility has yet to be substantiated by experiments.

References:

http://omp.gso.uri.edu/doee/biota/algae/phaeo/ecto.htm
http://www.elbalero.gob.mx/kids/bio/html/especies/algas/alga3.html