Department of Plant Science, Macdonald Campus of McGill University, 21,111 Lakeshore Rd., Ste-Anne-de-Bellevue, Québec, H9X 3V9, Canada
Colletotrichum coccodes is a biocontrol agent of velvetleaf (Abutilon theophrasti), a noxious weed of corn and soybean. Metallothioneins (MTs) and basic region/leucine zipper motif (bZIP) are heavy-metal-binding proteins and transcription factors, respectively, that have been related to several plant processes, including the responses of plants to pathogen attack. Previous investigation of the determinants involved in the velvet-leaf-C. coccodes interaction had shed light on particular plant and fungal genes expressed in this pathosystem. Here, we report on the temporal expression patterns of two distinct types (2 and 3) of MT and bZIP transcription factor genes in velvetleaf leaves following infection with C. coccodes using quantitative reverse-transcription polymerase chain reaction. Gene expression ratios were significantly upregulated 1 day after infection (DAI), a time at which velvetleaf leaves appeared symptomless. At 2 DAI, bZIP and type 3 MT expression ratios dropped to levels significantly lower than those estimated for noninfected plants. Necrotic symptoms appeared 5 DAI and increased with time, during which gene expression levels were maintained either below or at levels observed in the control. These findings indicate that C. coccodes altered the expression of type 2 and 3 MT and bZIP genes. In addition, this is the first report on induction of a type 3 MT in plants in response to a pathogen attack.