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Loss of cAMP-Dependent Protein Kinase A Affects Multiple Traits Important for Root Pathogenesis by Fusarium oxysporum

June 2011 , Volume 24 , Number  6
Pages  719 - 732

Hye-Seon Kim,1 Sook-Young Park,1 Sangwoo Lee,1 Elizabeth L. Adams,2,3 Kirk Czymmek,2,3 and Seogchan Kang1

1Department of Plant Pathology, The Pennsylvania State University, University Park 16802 U.S.A.; 2Delaware Biotechnology Institute, Newark, DE 19711 U.S.A.; 3Department of Biological Sciences, University of Delaware, Newark, DE 19716 U.S.A.

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Accepted 14 January 2011.

The soilborne fungal pathogen Fusarium oxysporum causes vascular wilt and root rot diseases in many plant species. We investigated the role of cyclic AMP-dependent protein kinase A of F. oxysporum (FoCPKA) in growth, morphology, and root attachment, penetration, and pathogenesis in Arabidopsis thaliana. Affinity of spore attachment to root surfaces of A. thaliana, observed microscopically and measured by atomic force microscopy, was reduced by a loss-of-function mutation in the gene encoding the catalytic subunit of FoCPKA. The resulting mutants also failed to penetrate into the vascular system of A. thaliana roots and lost virulence. Even when the mutants managed to enter the vascular system via physically wounded roots, the degree of vascular colonization was significantly lower than that of the corresponding wild-type strain O-685 and no noticeable disease symptoms were observed. The mutants also had reduced vegetative growth and spore production, and their hyphal growth patterns were distinct from those of O-685. Coinoculation of O-685 with an focpkA mutant or a strain nonpathogenic to A. thaliana significantly reduced disease severity and the degree of root colonization by O-685. Several experimental tools useful for studying mechanisms of fungal root pathogenesis are also introduced.

© 2011 The American Phytopathological Society