Understanding the chemical factors involved in the endophytism x pathogenicity of different Penicillium brasilianum isolates

Abstract

The complexity of nature is extraordinary; the ingenious mechanisms in which microorganisms co-exist in a beneficial (endophytes) or non-beneficial (pathogens) way with the host plant always intrigued scientists with fundamental questions: Why some microorganisms live in mutualistic or neutral association with the host and others assume a pathogenic character leading to plant diseases? What are the features that differentiate endophytes from pathogens? How endophytes bypass the plant defenses in order to colonize and co-exist in a beneficial association with the host? Although, there are intensive discussions in the literature, none of such intriguing questions have been answered so far. In order to address such ambitious questions, our group came up with a fungal-host model to gain deeper understanding in these fungal-host interactions. In our biological model, there are two different strains of Penicillium brasilianum, one isolated as endophyte from the plant Melia azedarach and the other presents pathogenic behavior against onion (Allium cepa). Interestingly, our group showed that the pathogenic strain was able to successfully re-infect the onion host, but the endophytic strain lead to an asymptomatic infection in onion. Although these two strains share great similarities, the genome comparison indicated differences at the natural products gene clusters level, which might result in different metabolic profiles. These observations might imply that secondary metabolites could be acting as virulence factors or mediating the endophytic-host association. Initial chemical studies in our group indicated the production of a particular secondary metabolite that was produced only by the endophytic strain, the opposite was also true, and we observed specific secondary metabolites produced only by the pathogenic strain. Therefore, we aim to progress in the studies of chemical-ecology aspects of endophytic and pathogenic interactions using P. brasilianum as biological model, elucidating the biologically active constituents of plant-pathogen and plant-endophyte interactions. Would natural products be important to determine if a fungus would be an asymptomatic endophyte or an aggressive pathogen? In order to accomplish such ambitious aims, our group will be conducting several chemical based, molecular biology and genetics studies. These studies will be invaluable for understanding plant-fungal interactions, pathogenesis and fungal colonization. The understanding of the mechanisms involved in endophytic and pathogenic associations would not only contribute to the fundamental understanding of the biological systems but it would also be an important step to develop strategies from fungal infections contributing to agriculture worldwide. (AU)