We have been investigating a disease called victoria blight of oats, which is caused by the fungus Cochliobolus victoriae. The fungus is pathogenic because of its ability to produce the host-selective toxin, victorin. Victorin is composed of a group of structurally related cyclized pentapeptides. The most abundant component of victorin in culture filtrates, victorin C, has a molecular weight of 814 and is composed of glyoxylic acid, 5,5-dichloroleucine, threo-β-hydroxylysine, erythro-β-hydroxyleucine, α-amino-β-chloroacrylic acid, and 2-alanyl-3,5-dihydroxy-⌂2-cyclopentenone-1. Sensitivity to victorin, and thus, susceptibility to the fungus, is controlled by a dominant allele at the Vb locus. Furthermore, the Vb gene is either closely linked or identical to the Pc-2 gene, which confers resistance to the crown rust pathogen Puccinia coronata. Thus, it is anticipated that identification of the product of the Vb gene, a putative toxin receptor, will simultaneously identify the product of the Pc-2 rust resistance gene. We have identified two proteins, referred to as victorin binding proteins (VBP), which bind biologically active, radiolabelled victorin in vivo. One protein, a 100-kDa VBP, binds victorin in vivo only in toxin-sensitive, susceptible genotypes. The other VBP, a 15-kDa protein, binds victorin in vivo in both susceptible and resistant genotypes. We have isolated and characterized the 100-kDa VBP and have recently identified, in vitro, a 15-kDa VBP. Both of these proteins are components of the multienzyme complex, glycine decarboxylase. Current investigations center on the role of this enzyme complex in toxin sensitivity. Key words: victorin, oats, toxin, glycine decarboxylase, resistance, susceptibility.
Deterioration of stone and concrete exposed to bird excreta – Examination of the role of glyoxylic acid
