20Chicken is the first agricultural animal to have a sequenced genome, but current kinase 21 annotations of Gallus gallus are overwhelmingly limited to the predictions generated 22 based on homology or isolated studies focused on specific kinases. Our approach used 2 23 chemical probes consisting of ATP and ADP derivatives binding to specific lysine 24 residues within the ATP-binding pocket of kinases. Collectively, we identified 188 25 chicken kinases and corresponding 267 peptides labeled with the ATP and ADP acyl 26 derivatives in chicken spleen and liver. The kinases identified here are publicly available 27 through the database, Chickspress genome browser 28 29 putative functions of these chicken kinases indicates that kinases identified in this study 30 might regulate hematological system development, necrosis, apoptosis, epithelial 31 neoplasm, and other processes. The identified tissue-specific expression atlas of active 32 chicken kinases along with the ATP binding sites of kinases provide the basis for the 33 development of specific drug targets for multiple chicken diseases as well as starting 34 point for inhibitor selectivity studies in this agriculturally important species. Moreover, 35 this study will support future studies focused on identifying the role of these kinases in 36 chicken growth, metabolism, and disease. 37 38 40 41 42 Chicken represents an essential source of protein. The U.S. poultry industry is the 43 largest in the world and continues to be a major supplier of meat and eggs. The world's 44 population growth is projected to surpass 9 billion by 2050, which mandates 3 45 intensification of the existing poultry operations. It is necessary to make improvements 46 in the breeding, management, and treatment of poultry to meet this projected higher 47 demand for food. A comprehensive understanding of the physiology and 48 pathophysiology of the chicken is critical for animal production. Chicken is the first 49 agricultural animal to have a sequenced genome (1), with a description of the protein-50 coding genes in the genome. Understanding the biological role of annotated gene 51 products, i.e., proteins require a description of their biological function. Like other non-52 model agricultural organisms, the current annotation of the protein-coding genes in the 53 chicken genome relies on computational predictions based on sequence similarity, 54 based on the ortholog conjecture that postulates functional similarity of orthologous 55 genes (2, 3). The dynamic response, regulation, and modification of the genome 56 ultimately governs complex phenotypes. The availability of the chicken genome 57 expedites knowledge discovery using genomics methodologies. A compendium of 58 omics approaches such as transcriptomics, proteomics, or metabolomics enables the 59 measurement of the genome-scale response of chicken at the RNA, protein, and 60 metabolite levels, respectively, to identify molecular mechanisms responsive to biotic 61 and abiotic perturbations. Several post-transcriptional regulatory mec...