Cover photograph (Copyright © 2006, American Society for Microbiology. All Rights Reserved.): Green fluorescent protein (GFP)-expressing and red fluorescent protein (RFP)-expressing Sinorhizobium meliloti attached to root hairs of transgenic Medicago truncatula expressing GFP::talin, which marks the actin cytoskeleton. Note the deformations displayed by some of the root hairs in response to bacterial Nod factor, which is synthesized under control of the transcription activator NodD. (Image provided by Dan Gage, Department of Molecular and Cell Biology, University of Connecticut.) (See related article on page 5417.)