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Poster: Biology & Disease Mgmt: Mycology


Oxygen and an aerial state are independently required for asexual development of Aspergillus species
M. CHI (1), K. Craven (2) (1) The Samuel Roberts Noble Foundation, U.S.A.; (2) The Samuel Roberts Noble Foundation, U.S.A.

Asexual sporulation is one of the primary means for aerial dissemination of many plant pathogenic fungi. The generation of asexual spores usually involves dynamic changes in cellular polarity and morphogenesis (e.g. from filamentous hyphae to oval spores). While sporulation appears to be suppressed in planta, it is seemingly de-repressed outside of plant tissues, where it encounters an aerial environment. In this study, we identify key components that allow fungi to distinguish between in planta and aerial environments. We observed conidiophore development of several Aspergillus species in an artificial environment that mimicked the in planta condition, but where we could enforce either high or low oxygen conditions. This experimental design enabled us to reveal that not only oxygen but also the physical, aerial state are positive environmental factors inducing conidiogenesis in most of the aspergilli tested in this study. Transcriptional analysis combined with direct observation of conidiation-defective mutants revealed that expression of key regulatory genes for conidiophore development is indeed regulated by these environmental cues and that the production of reactive oxygen species is required for polarized cell differentiation. Our findings provide not only novel insights into how fungi respond to an aerial environment but also inform an improved model for the regulatory pathway controlling conidiophore development.