Analysis of the expression pattern of the defensin gene in the lepidopteran Mamestra brassicae

Abstract

Southern blotting experiments performed on Mamestra brassicae genomic DNA after digestion with methylation-sensitive restriction enzymes indicated that defensin gene is methylated at CpG targets in the promoter region. However, defensin gene is actively transcribed despite the presence of methylation. Experiments performed by genome demethylation indicated that demethylated defensin gene resulted in an altered expression after bacterial induction. In particular, no increase in gene expression was observed after induction with Gram positive bacteria if defensin gene was demethylated. The present results are intriguing since they indicate that in M. brassicae DNA methylation is not involved in gene silencing, but also that DNA methylation could be essential to assure the expression of specific genes. On the whole, data here presented argue against an unifying and evolutionary conserved role of cytosine methylation from invertebrates to vertebrates.