Molecular Phylogeny of Entomopathogens

Abstract

Insects, like other organisms, are susceptible to a variety of diseases caused by bacteria, viruses, fungi, protozoan and nematodes. Insect pathogens show a wide variety of interactions with their hosts that facilitate their replication and transmission, including strategies for evading the host's defences towards invasion of microorganisms, and for manipulating their hosts physiology and behaviour. By applying a wide range of molecular techniques and approaches, better understandings of these interactions and of the roles played by both host and virulent genes have been understood. The control of insect pests with entomopathogens is an unique approach, in that naturally occurring host-pathogen relations are manipulated to the benefit of man, protecting agricultural crops and forests or controlling insect vectors of diseases. The isolation and identification of a pathogen followed by the phylogenetic classification of entomopathogens are the basic principles in insect pathology. Full genomic DNA sequencing techniques are used to assess the genetic diversity and phylogenetic analyses of entomopathogens. Alternatively, specific genes of interest can be targeted for sequencing. Sequences of single gene have been extensively used to assess phylogenetic relationships of known and novel isolates. However, the lack of sufficient resolution and disagreement with other gene phylogenies has prompted investigation of other genes and methods to further explore evolutionary relationships of entomopathogens. Therefore, phylogenies based on combined sequences of shared genes or the complete genome sequencing have been found to be more robust, providing more phylogenetic information and increasing robustness of evolutionary hypotheses. With the increasing efficiency and lower cost of whole genome sequencing, whole-genome studies of entomopathogens will refine knowledge about their evolutionary history and enable direct insight into the biology of entomopathogenesis.