Aspartic proteases gene family in rice: Gene structure and expression, predicted protein features and phylogenetic relation.

Aspartic proteases constitute a large family in eukaryotes, which play fundamental roles in protein processing, maturation and degradation. In this study, we identified 96 OsAP genes in rice (Oryza sativa L.), the model plant for monocots, by a reiterative database search. The analysis of the complete set of OsAP genes is presented, including chromosomal location, phylogenetic relationships, classification and gene structure. Moreover, a comprehensive expression analysis of OsAP family genes was performed using 24 tissues during the plant life cycle of two rice cultivars. Sixty-six OsAP genes were found to be expressed in at least one of the examined developmental stages, which were divided into 3 classes based on their transcript levels. OsAP genes were also found to be differentially up- or down-regulated in rice seedlings in response to treatments with phytohormones, as well as in plumules/radicles under light/dark conditions. The comprehensive annotation and expression profiling undertaken in this research add to our understanding of OsAP family genes in rice growth and development. Our results also provide a basis for selection of candidate genes for functional validation in future studies.