coli conditional auxotrophs. These proteins do not bear significant sequence similarity to naturally occurring proteins, are α-helical, as per our binary code design strategy, and are extremely thermostable. Our work demonstrates that even de novo polypeptides are genuinely poised for biological action and that unevolved proteins from a binary coded combinatorial library will readily promote life. E-mail:

mafisher@princeton.​edu Origin of Plant Phenylalanine Ammonia Lyase: A Key Apoptosis inhibitor Event for Land Colonisation? Marco Fondi1, Giovanni Emiliani,2 Simonetta Gribaldo3, Renato Fani1 1Department of Evolutionary Biology, University of Florence, via Romana 19, 50125 Florence Italy; 2Department of Environmental and Forestry Technologies and Sciences, University of Florence, via S. Bonaventura 13, 50145 Florence, Italy; 3BMGE

Unit, Pasteur Institute, 75724 Paris, France Between 480 and 360 million years ago, land plants (Embryophytes) evolved, from the Charophyceae, a small group of freshwater green algae (Kenrick and Crane,1997), differentiating from simple structure (Bryophyte) to elaborate organisms showing an extraordinary array of complex organs and tissue systems (vascular plants). However, in the first stages of prototrophs terrestrialization, beneficial associations between fungi (mycorrhizal symbioses), and soil bacteria (N2 fixing), might have greatly helped early land plants to face a harsh environment characterised by important stresses including desiccation, UV radiation, and microbial attack (Selosse and Le Tacon, 1998). A key find more event for plants colonisation of land and diversification was probably represented by the molecular evolution of phenylpropanoid pathway, since these compounds are involved in many

stress response pathways (pathogens, grazing, ROS scavenging, UV screening, etc) as well as in other fundamental traits such as biosynthesis of lignin, the structural polymer able to guarantee stem rigidity and xylem (water conducting tissue) formation (Ferrer et al., and reference Amino acid therein). Despite its importance, the origin and evolution of the phenylpropanoid pathway, as well as the first advantageous physiological roles of its products are unclear. Phenylalanine Ammonia Lyase (PAL) is responsible for the first committed step of plant phenylpropanoid pathway and the complete metabolism appears to be a specific and ubiquitous feature of land plants. However, PAL SAR302503 datasheet homologues have been identified and characterized in fungi such as Aspergillus oryzae (Seshime et al., 2005). Although phenylpropanoids are largely absent in prokaryotes, PAL homologues have been recently identified in Streptomyces maritimus and Photorhabdus luminescens where they are involved in the production of antimicrobial compounds (Xiang and Moore, 2005).