Genome-Wide Analysis of Thionin Genes in Higher Plants

The thionins (α/β and γ) are one of the most important antimicrobial peptides in broad-range plant defense system in many monocot and dicot plant species. Therefore, understanding the biological role of these proteins is very important in terms of improving crop productions and developing effective pesticides. In this study, a total of 56 thionin protein sequences for 14 different monocot and dicot plant species were analyzed in silico. With a few exceptions, it was observed that usually proteins with gamma-thionin domain (PF00304) (72-120 amino acid length; pI=5.45-9.38) structure were relatively shorter and more basic than that of the proteins with thionin domain structure (PF00321) (109-148 amino acid length; pI=5.23-7.91). In addition, proteins with thionin domain structure are more similar between themselves than that of the proteins with gamma-thionin domain structure. The sub-cellular locations of all proteins were predicted as extracellular and unique motif pattern for all species was not detected. The constructed phylogenetic tree was arbitrarily divided into two main groups (A and B) according to their domain families since all the proteins with gamma-thionin domain were clustered in group A and all the proteins with thionin domain were in group B. Based on the secondary structure analysis, all the proteins belonging to thionin domain family had two α-helices and two β-strands while the proteins with gamma-thionin family had two β-strands in Populus trichocarpa and three β-strands in Brassica rapa and Solanum lycopersicumwith one α-helix. Also, some structural divergences were detected in tertiary structure of gamma-thionin proteins.