Abstract: 20S proteasome is able to maintain cellular protein homeostasis by specifically degrading proteins in the cytoplasm and nucleus either by itself or by the ubiquitin-proteasome system. In this study，21 members of the 20S proteasome gene family of tomato（Solanum lycopersicum L.）were identified and bioinformatically analyzed. The results showed that most of the genes of the tomato 20S proteasome contain similar promoters and introns，with the genes encoding the α-subunit being better conserved and those encoding the β-subunit being poorly conserved；Subcellular localisation reveals that the majority of genes function in the cytoplasm；Chromosomal localisation and gene duplication analyses revealed that the 21 20S proteasome genes were unevenly distributed across 12 chromosomes，with the presence of two fragment duplication gene pairs；Evolutionary analyses showed that genes encoding the α-subunit and β-subunit were classified in different taxa or subgroups；Multi-species colinearity analysis revealed more homologous gene pairs between chili（Capsicum annuum L.），potato（Solanum tuberosum L.），and tomato. However fewer homologous gene pairs between Arabidopsis，rice（Oryza sativa L.），maize（Zea mays L.），and tomato. SlPRA1-01，SlPRA10-04，SlPRA11-05，and SlPRA16-09 formed gene pairs in three species. Promoter and tissue-specific expression analyses revealed that the 20S proteasome gene family exhibited important role in tomato adversity stress and growth and development.

Key words: tomato, 20S proteasome, ubiquitin-proteasome system, bioinformatics analysis