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Received April 15, 2014; Revision received April 28, 2014
Protease inhibitors (PIs) are generally small proteins that have been identified in plants. The wip1 gene codes for wound-induced protein, which is similar to serine PIs of the Bowman–Birk family (BBIs). In this study, we analyzed 10 wip1 genes of Turkish maize varieties to understand the structure and characteristics of the wip1 genes and proteins in maize. We found that genetic variability of wip1 genes was higher (π: 0.0173) than reported in previous studies. Tajima’s D value was found to be positive (1.73), suggesting over-dominant selection in these loci. According to phylogenetic analysis of wip1 proteins, monocot and dicot BBIs were separated independently, and Turkish varieties were clustered with each other generally. The 3D structures of wip1 proteins indicated that several wip1 proteins had structural divergence in active loops, containing various numbers of cysteine residues ranging between 7 and 9. Particularly, Cys74 was identified in Kocbey and Gozdem varieties, whereas Cys98 was only in the Gozdem variety. Also, a critical serine residue (Ser98) was observed in two varieties – Antbey and Batem Efe. These results can contribute to understanding the role of wip1 genes and corresponding proteins in maize.
KEY WORDS: protease inhibitors, wound-induced protein, Bowman–Birk family, Turkish maize