Resistance to prasinoviruses analysed by transcriptomics and recombination – REVIREC

Algal genes that control resistance or susceptibility to viruses will be identified: (i) genes of algae and viruses expressed during the infectious cycle of the viruses will be analyzed by high-throughput sequencing (RNAseq) and using proteomic techniques, (ii) complete genomes of many strains of algae resistant mutant viruses will be acquired by NGS (Illumina), (iii) study of recombination between viral genes to identify features involved in virulence / adaptation of a virus on its host, (iv) use of genetic transformation to overexpress or block the genes of interest.

In this initial phase, we have been acquiring knowledge, developing synchronous algal cultures, fresh viral lysates, and methodologies necessary to analyse the infection in defined cell cycle conditions (Partner1). We have completed an analysis of the codon usage in the host and the virus, and a review of marine viruses (see below). Partner 2 began the analysis of viral capsid proteins.

At six months, we have long way to go to achieve our goals, but our outlook for our progress in this research area are good.

We have completed work on the codon usage (1), useful for understanding gene expression hosts and their viruses. Writing a revue (2) allowed us to review the state of the art of the subject.
(1) Michely, S. et al. Evolution of Codon Usage in the Smallest Photosynthetic Eukaryotes and Their Giant Viruses. Genome Biol Evol 5, 848-859 (2013).
(2) Grimsley, N. H. et al. in Advances in Botanical Research (Ed. Gwenaël Piganeau) Volume 64, 343-381 (Academic Press, 2012).

Phytoplankton forms the basis of the food web, and affect biogeochemical cycles and global climate. Unicellular eukaryotes form an active and important part of this diverse reservoir of life, and can be infected by viruses, that thereby control blooms and shape the evolution of biodiversity in phytoplankton, but little is known about their biological functions. Viruses often show strict host strain specificity. This is a crucial factor for determining their impact on phytoplankton populations, but nothing is known about the molecular mechanisms involved in this specificity. The Mamiellales-prasinovirus interaction, where the complete genomes of numerous viruses and their host algal species have been characterised, offers an unparalleled opportunity for integrative interdisciplinary biological analyses. REVIREC aims to describe the molecular processes of these interactions, and investigate both host and viral genes involved in susceptibility and resistance to viruses. Specifically this project will address (i) the time course of biological functionalities involved in host-virus interactions by transcriptomic and recombinational approaches, and (ii) the identification and characterisation of host and viral genes controlling resistance or susceptibility. The phenotypical effects of genes identified by genetical, bioinformatical, statistical and transcriptional analyses will be tested by transformation to assess their biological roles in the interaction, providing important parameters future ecosystem modelling.