CEL1, PROBABLY ENCODING A CELLOBIOHYDROLASE LACKING THE SUBSTRATE-BINDING DOMAIN, IS EXPRESSED IN THE INITIAL INFECTION PHASE OF CLAVICEPS-PURPUREA ON SECALE-CEREALE

At the host-pathogen interface of hyphae penetrating host cell walls i n the rye ovary, a lack of cellulase-gold labeling of beta-1,4-glucan in host cell walls indicates that enzymatic degradation of cellulose m ight be an important factor during the infection of rye by Claviceps p urpurea. Using cbhI from Trichoderma reesei as a probe, a putative cel lulase gene (cell) was isolated from a genomic library of the C. purpu rea strain T5. The coding region of 1,616 bp contains two introns and a putative signal peptidase cleavage site, leaving a coding capacity o f 437 amino acids for the mature protein. The derived amino acid seque nce shares significant homology with other fungal cellobiohydrolases a nd lacks the substrate binding domain. Expression analysis using rever se transcriptase-polymerase chain reaction (RT-PCR) shows that cell is induced during the first days of infection of rye by C. purpurea. It may be involved in the penetration and degradation of host cell walls by depolymerizing plant beta-1 4-glucan and, therefore, play a role in the infection process.