Cloning and expression of genes involved in conidiation and surface properties of Penicillium camemberti grown in liquid and solid cultures

Based on bioinformatic data on model fungi, the rodA and wetA genes encoding, respectively, a RodA hydrophobin protein and the WetA protein involved in conidiation mechanisms, were PCR-cloned and characterized for the first time in Penicillium camemberti. These results, completed by a sequence of the brlA gene (available in GenBank), which encodes a major transcriptional regulator also involved in the conidiation mechanism, were used to compare, by qRT-PCR, the expression of the three genes in liquid and solid cultures in a synthetic medium. While expression of the brlA and wetA genes increased dramatically in both culture conditions after 4 days of growth, expression of the rodA gene increased only with conidiation and in the solid culture, and this expression was correlated with production and secretion of a RodA protein outside the hyphae, which became very hydrophobic. In liquid cultures, no production of RodA occurred in mycelia, which remained hydrophilic, and no conidiation was detected despite formation of swellings at the tips of hyphae. The absence of conidiation in liquid culture correlated with the lack of rodA gene expression, which could be regulated by the medium composition independently of brlA and wetA genes expression.