Activation of genes in barley roots in response to infection by two Drechslera graminea isolates

The inoculation of barley rootlets by two isolates of Drechslera graminea activates a specific set of the plant’s genes. Within 24 h of pathogen inoculation, eight new mRNAs had accumulated, although after 96 h only three were still detectable. Northern blot analysis showed the accumulation of three mRNA families in response to inoculation. Within 6 h of contact, the fungus induced a class of transcripts homologous to a clone coding for peroxidase. A second class of mRNAs corresponding to a clone encoding thaumatin-like protein was detected after 18 h, but with differing induction kinetics for the two isolates indicating that expression is controlled by an isolate-specific component. A third class of mRNAs for a clone encoding thionin was accumulated at the same stage, although the expression of these translated products was influenced less by the Drechslera graminea isolate than by the barley cultivar tested. The potential role of the three genes is discussed.