A Biochemical Phenotype for a Disease Resistance Gene of Maize.
In maize, major resistance to the pathogenic fungus Cochliobolus (Helminthosporium) carbonum race 1 is determined by the dominant allele of the nuclear locus hm. The interaction between C. carbonum race 1 and maize is mediated by a pathogen-produced, low molecular weight compound called HC-toxin. We recently described an enzyme from maize, called HC-toxin reductase, that inactivates HC-toxin by pyridine nucleotide-dependent reduction of an essential carbonyl group. We now report that this enzyme activity is detectable only in extracts of maize that are resistant to C. carbonum race 1 (genotype Hm/Hm or Hm/hm). In several genetic analyses, in vitro HC-toxin reductase activity was without exception associated with resistance to C. carbonum race 1. The results indicate that detoxification of HC-toxin is the biochemical basis of Hm-specific resistance of maize to infection by C. carbonum race 1.
Meeley
R. B.
RB
Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824-1312.
Johal
G. S.
GS
Briggs
S. P.
SP
Walton
J. D.
JD