Genome-wide analysis of the cupin superfamily in cowpea (Vigna unguiculata)

Cowpea [Vigna unguiculata (L.)Walp.] is an essential food crop that is cultivated in many important arid and semi-arid regions of the world. In this study the genome-wide database of cowpea genes was accessed in search of genomic sequences coding for globulins, specifically members of the cupin superfamily, a well-documented multigenic family belonging to the globulin protein class. A total of seventy-seven genes belonging to the cupin superfamily were found and divided into six families. We classify V. unguiculata genes into two subgroups: classical cupins with one cupin domain (fifty-nine proteins) and bicupins with two cupin domains (eighteen members). In addition, a search for cupin members in other closely related species of the fabaceae family [V. angularis, V. radiatam and Phaseolus vulgaris (common bean)] was performed. Based on those data, a detailed characterization and comparison of the cupin genes on these species was performed with the aim to better understand the connection and functions of cupin proteins from different, but related, plant species. This study was the first attempt to investigate the cupin superfamily in V. unguiculata, allowing the identification of six cupins families and better understand the structural features of those proteins, such as number of domains alternative splicing.