2011a,b). Furthermore, endosymbionts may play a nutritional role for sponges by producing hydrolytic enzymes able to convert complex organic matter swirled into the host by filter feeding into easily accessible nutritional sources (Selvin et al. 2010). On the other hand, microbial symbionts presumably benefit from their sponge hosts which offer generous nutrient supply, as well as protection from predators

or high levels of light within sponge tissues (Taylor et al. 2007). It was suggested that disturbances in symbiosis due to environmental stress may affect sponge health, growth rates or resistance to predation, fouling selleck screening library and disease (Webster and Taylor 2012). Similarly, observed shifts in the composition of diverse and metabolically active endosymbionts inhabiting corals in response to environmental find more changes indicated their possible contribution to the ability of their hosts to adapt or acclimatize to climate changes or environmental stress (Reshef et al. 2006; van Oppen et al. 2009). This fact gains enormous interest considering currently observed rapid environmental changes and degradation of marine ecosystems (Webster and Taylor 2012). Fungal-host communication Symbiotic microorganisms must have evolved to overcome or manipulate host defence systems in order to be able to establish a stable association with their hosts (Pieterse and Dicke 2007; Robert-Seilaniantz

et al. 2007). The latter is assumed to be mediated by biochemical and/or genetic communication between symbionts and hosts, where a specific form of communication probably results in the expression of a symbiotic interaction under particular environmental factors (Singh et al. 2011). Examples include disturbing the defense signaling network of host plants, or reprogramming host

metabolism by modifying Fenbendazole hormonal homoeostasis and antioxidant contents (Robert-Seilaniantz et al. 2007; Göhre and Robatzek 2008). Interestingly, most pathogens and mutualists share the same initial phases of infection and colonization (Rodriguez et al. 2004). Hence, plants probably differentiate between beneficial and harmful microbes by specific recognition and early signalling processes and consequently determine the kind of interaction expressed (Singh et al. 2011). The increase of intracellular calcium levels in plant cells, a second messenger in numerous plant signaling pathways, was found to be one of the early signalling events following infection. Potential pathogens activate plant defense responses through receptor-mediated cytoplasmic calcium elevation, which through a signal chain of events results in defense-related gene induction and phytoalexin accumulation by activation of ion fluxes at the plasma membrane (H+/Ca2+ influxes, K+/Cl− effluxes), an oxidative burst and MAPK activation (Blume et al.