Cloning and Characterization of Cyclotide-like Genes in Zea mays

Cyclotides-like proteins are a family of small disulfide-rich and plant-derived peptides made up of ~30 amino acids. They contain a unique structural motif that consists of a head-to-tail cyclic backbone and knotted arrangement of three disulfide bonds, together referred to as the cyclic cystine knot (CCK). The cyclotides are antimicrobial circular peptides that have a variety of biological activities such as anti-HIV, anti-tumor, cytotoxic, hemolytic activity and etc. In current study, we have cloned new members of the cyclotide-like gene family from Zea Mays leaf cDNA using 3'RACE-PCR and specefic primers based on sequences found in a continuous region of homology present in EST database. Clones were randomly picked and sequenced. Nine cyclotide-like genes were identified. Phylogenetic analysis divided them in two separate classes; first class with length 300-500nt showed similarity with classical cyclotide-like genes in databases. In contrast the other class was very different with length 90-500nt and showed variations in number of disulfide bands. The cloning of these genes in maize showed that they are very diverse and may have important role in plant response to different stresses.