Penicillium oxalicum putative methyltransferase LaeA is required in glycoside hydrolases gene expression during late phase of development

Penicillium oxalicum is an industrial producer of lignocellulolytic enzymes that degrade lignocellulosic polysaccharides to soluble sugars, which can be fermented to biofuels. LaeA is considered as a putative protein methyltransferase and is found involved in glycoside hydrolases gene expression. During the early phase of cultivation, ΔlaeA showed identical glycoside hydrolases gene transcription level compared with P. oxalicum wild type. However, remarkably decrease in glycoside hydrolases gene transcription level was observed in ΔlaeA after two days cultivation, accompanying with the reduction of extracellular lignocellulolytic enzyme protein. In xlnR overexpression strain which showed increased cellulase production, laeA deletion (OExlnRΔlaeA) led identical glycoside hydrolases gene expression model just as ΔlaeA. It is assumed that LaeA is required in the process that XlnR functions as a transcription activator. ΔlaeA strain also showed delayed conidial germination and drastically reduced conidiation compared with the parent strain. The defect in conidiation in ΔlaeA could be attributed to the reduced expression of transcription factor BrlA. In summary, LaeA plays important roles in development and extracellular lignocellulolytic enzyme production in P. oxalicum.

Keywords: Penicillium oxalicum; LaeA; lignocellulolytic enzyme; conidiation