Expression plasticity of Phlebotomus papatasi salivary gland genes in distinct ecotopes through the sand fly season

The majority of investigated genes were up-regulated in specimens from Swaymeh late in the season, when the availability of sugar sources is reduced due to water deprivation. On the other hand, these genes were not up-regulated in specimens collected from Aswan, an irrigated area less susceptible to drought effects.Expression plasticity of genes involved with vectorial capacity in disease vectors may play an important epidemiological role in the establishment of diseases in natural habitats.Many studies have demonstrated an environmental role in gene expression. Differential gene expression can be caused by biotic (e.g., virus infections and menopause in humans) or abiotic factors (e.g., arsenic poisoning and diesel exposure in humans; or temperature variation in worms and plants). Effects of the environment on gene expression are referred to as gene-by-environment-interactions, and the response displayed by organisms to such environmental change, phenotypic plasticity [1]. Although much is known about the ecology of the sand fly Phlebotomus papatasi [2-9], how the environment influences gene expression in this insect remains largely unexplored [10].Phlebotomus papatasi is the primary vector of Leishmania major in Northern Africa and the Middle East [11,12]. The behavior of this sand fly species is well documented with regards to resting places [12], blood sources [13] and dispersal ability [9]. In addition to blood, sugar also constitutes a key component of the sand fly life cycle, and several plant species are able to attract sand flies. In the Middle East, Prosopis farcta, Capparis spinosa, Ricinus communis, Solanum nigrum, and Rochia indica are some of the most attractive plants for P. papatasi [2]. Analyses of sugar contents in the gut of field caught flies revealed that 15.5% of the flies were fed on some type of sugar, and 22.5% of them presented cellulose shreds within their guts. Starch is also an important nutrient for P. papatasi, as demonstrated by the f