Intronless genes, as a characteristic feature of prokaryotes, are an important 
resource for the study of the evolution of gene architecture in eukaryotes. In 
the study, 14,623 (36.87%) intronless genes in maize were identified and the 
percentage is greater than that of other monocots and algae. The number of maize 
intronless genes on each chromosome has a significant linear correlation with 
the number of total genes on the chromosome and the length of the chromosomes. 
Intronless genes in maize play important roles in translation and energy 
metabolism. Evolutionary analysis revealed that 2601 intronless genes conserved 
among the three domains of life and 2323 intronless genes that had no homology 
with genes of other species. These two sets of intronless genes were distinct in 
genetic features, physical locations and function. These results provided a 
useful source to understand the evolutionary patterns of related genes and 
genomes and some intronless genes are good candidates for subsequent functional 
analyses specifically.