Another extended phenotype due to the presence of Wolbachia is observed in the parasitoid wasp Asobara tabida (Hymenoptera: Braconidae),

in which aposymbiotic females exhibit a strong developmental defect. Surprisingly, Wolbachia has become necessary for egg production in this wasp, since aposymbiotic females are unable to produce viable JQ1 concentration offspring [6]. Interestingly, A. tabida is the only member of the genus Asobara to be dependent on Wolbachia for oogenesis, which suggests that the dependence has evolved recently, and makes it possible to study the molecular mechanisms underlying this transition. In addition, polymorphism of the ovarian phenotype is observed in natural populations after the elimination of Wolbachia: some aposymbiotic females do not produce eggs, whereas others produce a few eggs that die prematurely [7, 8]. This polymorphism constitutes a tool to better understand the influence of these molecular

mechanisms on the severity of the ovarian phenotype and on the evolution of dependence. At a mechanistic level, cytological analysis of the ovarian phenotype has begun to shed light on the mechanisms underlying dependence in A. tabida. Indeed, eliminating Wolbachia triggers programmed cell death (PCD) in the egg chambers within the ovaries of A. tabida females [9]. As egg production is tightly controlled by two main apoptotic checkpoints EGFR inhibitor during oogenesis [10], the deregulation of PCD in aposymbiotic wasps must result in female inability to complete oogenesis. Because selleck products PCD is frequently involved in infection processes by bacterial pathogens [11], it has been hypothesised that a mechanism underlying the maintenance of Wolbachia at the individual level may have given rise to the evolution of dependence through its pleiotropic role in immunity and development [12]. This hypothesis is supported by recent findings showing that consequences

of Wolbachia infection in insects may extend far beyond the classical effect on reproduction, by impacting host physiology and immunity. Wolbachia could play a role as a nutritional mutualist, by influencing iron utilization by its Drosophila hosts [13, 14]. Wolbachia infection has also been shown to generate oxidative stress in one Aedes aegypti cell line, which reacts by the over-expression of host antioxidant genes [15]. Interestingly, Reactive Oxygen Species (ROS) are known to play a major role in immunity as a first line of defence [16] but also as a mechanism insuring microbe homeostasis [17]. Finally, Wolbachia is known to confer resistance against RNA viral infection in D. melanogaster and D. simulans [18, 19], and against various pathogens in the mosquito A. aegypti, notably by priming the innate immune system [20, 21]. To summarize, increasing evidence is emerging on the phenotypic effects of Wolbachia infection on host physiology and immunity [18, 19, 22].