Adaptation of turnip mosaic potyvirus to a specific niche reduces its genetic and environmental robustness.

Anamarija Butković,Rubén González,Inés Cobo,Santiago F Elena

doi:10.1093/ve/veaa041

Abstract

Robustness is the preservation of the phenotype in the face of genetic and environmental perturbations. It has been argued that robustness must be an essential fitness component of RNA viruses owed to their small and compacted genomes, high mutation rates and living in ever-changing environmental conditions. Given that genetic robustness might hamper possible beneficial mutations, it has been suggested that genetic robustness can only evolve as a side-effect of the evolution of robustness mechanisms specific to cope with environmental perturbations, a theory known as plastogenetic congruence. However, empirical evidences from different viral systems are contradictory. To test how adaptation to a particular environment affects both environmental and genetic robustness, we have used two strains of turnip mosaic potyvirus (TuMV) that differ in their degree of adaptation to Arabidopsis thaliana at a permissive temperature. We show that the highly adapted strain is strongly sensitive to the effect of random mutations and to changes in temperature conditions. In contrast, the non-adapted strain shows more robustness against both the accumulation of random mutations and drastic changes in temperature conditions. Together, these results are consistent with the predictions of the plastogenetic congruence theory, suggesting that genetic and environmental robustnesses may be two sides of the same coin for TuMV.

Highlights

RNA viruses are very successful parasites that infect hosts across all biological kingdoms.This evolutionary success results from their evolvability, which in turn depends on the combination of three factors, namely high mutation rates, short generation times and very large population sizes
This means that: (i) they will increase in frequency only at very high deleterious mutation rates because genotypes without these robustness-conferring mutations will suffer stronger mutational loads. (ii) They will slow down the rate of adaptation by buffering the effect of other linked beneficial mutations
Fast appearance of symptoms and a large number of infected plants are reflected in larger area under the disease progress stairs (AUDPS) values, confirming AUDPS provides a good proxy to the degree of adaptation of a particular viral genotype to its host and environmental conditions

Summary

Introduction

RNA viruses are very successful parasites that infect hosts across all biological kingdoms This evolutionary success results from their evolvability, which in turn depends on the combination of three factors, namely high mutation rates, short generation times and very large population sizes. Any mutation increasing genetic robustness will hardly rise in frequency because they have no other phenotypic effect than buffering the effect of other mutations (de Visser et al 2003) This means that: (i) they will increase in frequency only at very high deleterious mutation rates because genotypes without these robustness-conferring mutations will suffer stronger mutational loads. Mutation accumulation in small populations may select for genetic robustness (Krakauer and Plotkin 2002; Forster et al 2006; Elena et al 2007), though a low population size would reduce the effectiveness of selection (Forster et al 2006; Elena et al 2007)

Methods

Results

Discussion

Conclusion