Reporter genes allow for the identification of transformed cells without the need for selective media, as they encode proteins that are more readily apparent. The gus gene, encodes the enzyme β-glucuronidase, is extensively used as a marker of plant transformation. Related Theory Silencer is a DNA sequence capable of binding transcription regulation factors, called repressors. DNA contains genes and provides the template to produce messenger RNA (mRNA). Thus, silencers prevent genes from being expressed as proleins.