Abstract

The host range of a virus is defined as the number of species a virus potentially infects. The specialist virus infects one or few related species while the generalist virus infects several different species, possibly in different families. Origin of generalist viruses from their specialist nature and the expansion of the host range of the generalist virus occur with the host shift event in which the virus encounters and adapts to a new host. Host shift events have resulted in the majority of the newly emerging viral diseases. This review discusses the advantages and disadvantages of generalist over specialist viruses and the unique features of plant viruses and their hosts that result in a higher incidence of generalist viruses in plants.

Highlights

  • Viruses can infect all the life forms from archaebacteria to eubacteria, from Protista to algae, from plants to animals [1]

  • This review will summarise the evolutionary advantages and disadvantages of generalist viruses over specialist viruses, adaptive challenges faced by a virus during a host shift event and the unique features of plants and their viruses that promote the generalist nature of plant viruses

  • Host shift events are common in nature and lead to the evolution of generalist viruses both in animals and plants [7, 37, 47, 48]

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Summary

INTRODUCTION

Viruses can infect all the life forms from archaebacteria to eubacteria, from Protista to algae, from plants to animals [1]. The host shift event can result in the emergence of new diseases in both plants and animals and may cause huge economic loss and loss of lives. Pathogens host shifts have resulted in most of the recent emerging diseases in animals and plants [8, 10]. The analysis revealed that zoonotic pathogens are twice as likely to cause emerging diseases as non-zoonotic pathogens These pathogens are able to break the barriers of host shift events. Orthoreovirus is an example zoonotic virus having a wide host range It mainly infects mammals and some nonmammalian species of reptiles and birds [22]. Members of orthoreovirus have caused zoonotic infection in humans [23, 24] Another interesting example of a virus that causes recurrent zoonotic transmission is the influenza virus. This review will summarise the evolutionary advantages and disadvantages of generalist viruses over specialist viruses, adaptive challenges faced by a virus during a host shift event and the unique features of plants and their viruses that promote the generalist nature of plant viruses

ADVANTAGES AND DISADVANTAGES OF GENERALIST VIRUSES
Generalist Viruses have Lower Extinction Threats
Generalist Nature of Viruses Aids in their Evolution
Opportunity for the Generalist Virus to Acquire New Genetic Material
Generalist Viruses have Higher Fitness in a Dynamic Environment
Generalist Viruses Suffer from Fitness Trade-offs
Generalist Viruses are Disadvantageous in a Stable Environment
BARRIERS OF A HOST SHIFT EVENT BY A VIRUS
UNIQUE CASE OF PLANTS AND THEIR VIRUSES
Unrestricted Entry of Plant Viruses Inside the Plant Cells
Lack of a Dedicated and Robust Immune System in Plants
Majority of Plant Viruses are RNA Viruses with High Mutation Rates
Findings
CONCLUSION
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