FUNGAL-SPECIFIC AND PLANT-SPECIFIC GENE MARKERS TO FOLLOW THE BEAN ANTHRACNOSE INFECTION PROCESS AND NORMALIZE A BEAN CHITINASE MESSENGER-RNA INDUCTION

A bean-specific translation elongation factor (EF-1-alpha) and the Aspergillus nidulans actin gene were used to discriminate between bean (Phaseolus vulgaris) and Colletotrichum lindemuthianum RNA contents during a compatible anthracnose interaction. EF-1-alpha is constitutively expressed in cotyledonary bean leaves during mock infection. EF-1-alpha expression remains stable during the biotrophic phase of the infection process, but it drops rapidly during the necrotrophic phase at the time when the fungus actin transcript appears and accumulates. The EF-1-alpha gene expression was also used to normalize the induction kinetics of a bean basic chitinase. The results show that the adjustment modified the induction quantitatively by 2.5-fold and shifted the maximal expression by 8 hr when compared to the uncorrected curve. The consequences of these results are discussed in terms of infection processes.