Adenylyl Cyclase Plays a Regulatory Role in Development, Stress Resistance and Secondary Metabolism in Fusarium fujikuroi

The ascomycete fungus Fusarium fujikuroi (Gibberella fujikuroi MP-C) produces secondary metabolites of biotechnological interest, such as gibberellins, bikaverin, and carotenoids. Production of these metabolites is regulated by nitrogen availability and, in a specific manner, by other environmental signals, such as light in the case of the carotenoid pathway. A complex regulatory network controlling these processes is recently emerging from the alterations of metabolite production found through the mutation of different regulatory genes. Here we show the effect of the targeted mutation of the acyA gene of F. fujikuroi, coding for adenylyl cyclase. Mutants lacking the catalytic domain of the AcyA protein showed different phenotypic alterations, including reduced growth, enhanced production of unidentified red pigments, reduced production of gibberellins and partially derepressed carotenoid biosynthesis in the dark. The phenotype differs in some aspects from that of similar mutants of the close relatives F. proliferatum and F. verticillioides: contrary to what was observed in these species, ΔacyA mutants of F. fujikuroi showed enhanced sensitivity to oxidative stress (H2O2), but no change in heavy metal resistance or in the ability to colonize tomato tissue, indicating a high versatility in the regulatory roles played by cAMP in this fungal group

How plants might recognize rhizospheric bacterial volatiles

In contrast to animals, plants possess neither olfactory organs nor a central nervous system. However, they do perceive and systemically react to volatile stimuli. Such function serves in monitoring the immediate and remote environments and translates into optimized responses to biotic and abiotic stresses. While the ecological relevance of volatile-mediated plant–plant and plant–insect interactions is today unquestioned, both above- and below-ground plant–microbe communication through VOCs has only gained attention recently. The common metabolic origins that yield the vast chemical diversity of plant and microbes allow for a substantial overlap between plant and microbial volatile species. Hence, it remains unclear if plants recognize and/or distinguish plant-like from foreign cues. The identities of the cellular components ensuring such recognition are even more obscure. Easy-to-score plant outputs in response to microbial VOCs elicitation, like plant growth promotion and innate immunity stimulation, will be instrumental to pinpointing VOCs-sensing proteins. Several major phytohormones have a gaseous nature and dedicated perception machineries that could serve as a basis to envisage how volatile semiochemicals might be sensed by plants. If volatile-mediated communication represents an ancestral cellular feature, VOCs perception and signalling might rely on basal protein families and define a universal chemical language