Divergent and convergent evolution of housekeeping genes in human-pig lineage

Housekeeping genes are ubiquitously expressed and maintain basic cellular function across tissue/cell types conditions. The present study aimed to develop a set of pig housekeeping genes and compare characteristics of structure, evolution and function of housekeeping genes in the human-pig lineage. Using RNA sequencing data, we identified a list of 3,136 pig housekeeping genes. Comparing to human homologous counterparts, we found pig housekeeping genes were longer and subjected to slight weaker purifying selection pressure and faster neutral evolution. Common housekeeping genes, shared by the two species, have stronger purifying selection than species-specific genes. But pig-specific and human-specific housekeeping genes have similar functions. Some species-specific housekeeping genes have evolved independently to form similar protein-active sites or structure, such as classical catalytic serine-histidine-aspartate triad and zinc finger features, implying that they have converged for maintaining the basic cellular function, which led to equivalent solutions for adapting to the environment. Human and pig housekeeping genes have varied in their structure and gene list, but they have converged on the maintenance of basic cellular functions essential for the existence of a cell, regardless of its specific role in the species. The results shed light on the evolutionary dynamics of housekeeping genes.