1. Department of Biochemistry, Biophysics, and Molecular Biology (X.G., H.J., B.J.N.), National Science Foundation Engineering Research Center for Biorenewable Chemicals (X.G., B.J.N.), Department of Statistics (A.L., D.N.), Department of Genetics, Development, and Cellular Biology (L.L.), Laurence H. Baker Center for Bioinformatics and Biological Statistics (X.Z.), and Center for Metabolic Biology (B.J.N.), Iowa State University, Ames, Iowa 50011;