KAKUGO VIRUSES

Kakugo Viruses



Chapter 1: Introduction

Background of the study

The European honeybee Apis mellifera is a eusocial insect, living in families encompassing thousand individuals. Apiculture is an important economic resource in several countries for production of honey, wax, propolis and royal jelly. The insects have a nervous system with reduced complexity. Several honeybee behavioral traits have been linked to a genetic terrain, that includes stinging (Collins et al., 2010; Moritz et al., 2010), foraging for pollen or nectar (Hellmich et al., 2008; Robinson and Page, 2009), undertaking the removal of dead bees from the nest (Rothenbuhler 2010), and learning (Brandes 2008; Bhagavan et al., 2009).

Problem Statement

The attacking behavior of guard bees is self-sacrificing and is therefore considered to be a typical altruistic behavior exhibited by the workers (Wilson 2009). Thus, the honeybee is an attractive model for the study of altruistic aggressive behaviors (Fujiyuki et al. 2009). Quantitative trait locus analysis has been used to identify the loci related to aggressive worker behaviors (Hunt et al., 2009; Hunt et al., 2009). The genes responsible for the aggressive behaviors, however, have not yet been identified. Recently, Fujiyuki et al. (2009) studied the acquired aggressive behaviour of some bees against their natural enemy, the hornet Vespa mandarinia japonica. The aggressive behavior of the bees was not correlated to specific gene(s) but to the present ence of a novel picorna-like virus, genus iflavirus, termed Kakugo (ready to attack). Kakugo Virus (KV) RNA has been detected in the brains of aggressive worker honeybees, suggesting a tight correlation between cerebral localization of KV and the aggressive behavior of honeybees. KV is similar to another virus of honeybees, Deformed Wing Virus (DWV) transmitted via the bee mite, Varroa destructor. DWV infection occurs at the larval stage and is suggested to cause morphological deformity of wings in adult bees (DeJong et al., 2010; Schatton-Gadelmayer and Engels, 2009). KV and DWV RNAs differ in a few amino nucleotides and deletions (Fujiyuki et al., 2009) that are presumably responsible for the different virus-induced phenotypes in bees (Table 1).

Purpose of the study

The overall purpose of the proposed study will be to examine the insect picorna-virus translation mechanism. The virus to be examined in this proposed study is Kakugo viruses (KV). Additionally the aim of the present study was to investigate the presence of KV/DWV in the honeybees of five hives of Apulia and Basilicata, where aggressive behavior of honeybees had been observed.

Significance of the study

Single- stranded RNA viruses, infectious to the European honeybee, Apis mellifera L (see also Gene Therapy). are known to reside at low levels in colonies, with typically no apparent signs of infection observed in the honeybees. Reverse transcription- PCR ( RT- PCR) of regions of the RNA- dependent RNA polymerase ( RdRp) is often used to diagnose their presence in apiaries and also to classify the type of virus detected.

Analysis of RdRp conserved domains was undertaken on members of the newly defined order, the Picornavirales; focusing in particular on the amino acid residues and motifs known to ...