Effect of different carbon sources on proteases secreted by the fungal pathogen Sclerotinia sclerotiorum during Phaseolus vulgaris infection

Sclerotinia sclerotiorum (Sclerotiniaceae) is a plant pathogenic fungus that causes white mold disease in vegetable crops, including the common bean (Phaseolus vulgaris). Proteases produced by fungi are normally an important part of the pathogenic process in the host. We examined the effect of different carbon sources--pectin, glucose, and cell wall of P. vulgaris on the production of proteases in cultures of S. sclerotiorum. These proteases were also assayed in infected P. vulgaris plants. Enzyme activity was increased with all carbon sources, but the highest levels were found when pectin was added. Based on real-time quantitative reverse transcription-PCR analyses, protease induction in S. sclerotiorum was found to occur at the level of gene transcription. The finding of increased expression of acid phosphatase 1 and aspartyl protease in vivo in infected P. vulgaris plants supports the role of these enzymes in the invasion process of S. sclerotiorum.