Differential expression of chitin synthase (CHS) and glucan synthase (FKS) genes correlates with the formation of a modified, thinner cell wall in in vivo-produced Beauveria bassiana cells.

During infection (in vivo), the entomopathogenic fungus Beauveria bassiana produces yeast-like cells that are surrounded by modified cell walls. These modifications have been related to the fungus ability to limit recognition by the host defense system. The composition of the in vivo cell wall was analyzed using a combination of cytochemical and molecular techniques. The in vivo cell walls still contained both chitin and 1,3-beta-glucan, but they were significantly thinner than in vitro cell walls (50-60 nm versus 100-160 nm, respectively). The difference in cell wall thickness was correlated with transcriptional regulation of cell wall-related genes: quantitative RT-PCR reactions demonstrated that B. bassiana chitin synthase (CHS) and glucan synthase (FKS) genes are down regulated in vivo. These analyses indicate that in vivo-triggered phenotypic modifications, including cell wall adjustments, are controlled by molecular mechanisms that include regulation of gene expression at the transcriptional level.

Catalytic activity and expression of two flavin-containing monooxygenases from Drosophila melanogaster.

Two flavin-containing monooxygenase genes occur in the Drosophila genome (named DmFMO-1 and DmFMO-2). Differences exist between these two FMOs in: (1) genomic DNA architecture and predicted post-translational modifications; (2) recombinant protein solubility, activity, and absorbance spectra; and (3) subcellular distribution and developmental transcription/translation profiles in wildtype flies. Characteristic FAD absorbance spectra and strong catalytic competence in methimazole sulfoxidation were observed for recombinant DmFMO-2. Alternatively, weak sulfoxidation was observed for DmFMO-1, which correlated with reduced solubility in the recombinant system. Western blot analyses using specific antisera raised to each FMO showed the two FMOs to be immunologically distinct. In addition, Western blot analyses revealed FMO protein expression in both the microsomal and cytosolic sub-cellular fractions. Interestingly, a larger form of DmFMO-1 occurs in the cytosol that is most strongly expressed in the adult head. These findings suggest divergent physiological roles for DmFMO-1 and DmFMO-2. More specifically, it appears that DmFMO-1 has a distinct developmental role, while DmFMO-2 may have a general housekeeping function.