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Poster: Molecular & Cellular Plant-Microbe Interactions: MPMI


A Battle in a Kernel: Molecular Exploration of Antagonisms between Two Maize Endophytes, Fusarium verticillioides and Acremonium zeae
M. GAO (1), A. Glenn (2), S. Gold (2) (1) The University of Georgia, U.S.A.; (2) United States Department of Agriculture Toxicology and Mycotoxin Research Unit, U.S.A.

Fusarium verticillioides (Fv) is a prevalent seed-borne maize endophyte capable of causing severe kernel rot and fumonisin mycotoxin contamination. Within maize kernels, Fv is primarily confined to the pedicel, while another seed-borne fungal endophyte, Acremonium zeae (Az), is observed in embryos. Az produces two lactam-containing antibiotics, named pyrrocidine A (PA) and B (PB), with PA exhibiting greater inhibitory activity against Fv and other fungi. PA differs from PB only by having a double bond in the lactam ring, suggesting the importance of the lactam moiety for toxicity. Preliminary experiments indicated the fungus is able to metabolize PB. In the Fv genome, 38 out of the 46 identified lactamase domain-containing proteins are predicted to carry out lactam hydrolysis. We recently characterized one lactamase gene (FVEG_08291) essential for the hydrolysis of 2-benzoxazolinone, a maize phytoanticipin, that significantly induced the expression of this lactamase and adjacent clustered genes. Likewise, we predict that pyrrocidines will induce one or more lactamase gene(s) and that the encoded enzyme(s) will function to hydrolyze these Az metabolites. RNA-seq experiments are underway to assess the Fv transcriptional response to pyrrocidines and to Az co-inoculation. RNAseq data should allow us to identify the interacting lactamase gene(s) and help us better understand the molecular mechanisms underlying the metabolic antagonism between these endophytes.