Developed by personnel at the comparative genomics database Gramene and the maize model organism database MaizeGDB in collaboration with the Maize Genome Sequencing Project (MGSC), MaizeCyc is a catalog of known and/or predicted metabolic and transport pathways from maize (Zea mays ssp. mays). Pathways and genes presented in this catalog are based on the electronic and manual annotations of the B73 RefGen_v2 gene models. It includes various sequence-based associations provided by Gramene, MaizeSequence.org, and MaizeGDB to external database entries from EntrezGene, UniProtKB-SwissProt and GenBank. In this round, manual annotations of genes include mapping of classical phenotype genes to sequenced genomic loci provided by Schnable and Freeling, and proteomics-supported gene annotations from Friso et al (2010). The database was created using the Pathway Tools PathoLogic module developed by Peter D. Karp and coworkers at the Bioinformatics Research Group at SRI International.