In silicoCharacterization of Class II Plant Defensins fromArabidopsis thaliana

Abstract

Defensins compose a polyphyletic group of multifunctional defense peptides. The cisdefensins, also known as cysteine stabilized α β (CSαβ) defensins, are one of the most ancient defense peptide families. In plants, these peptides have been divided in two classes, according to their precursor organization. Class I defensins are composed by the signal peptide and the mature sequence, while the class II defensins have an additional C-terminal prodomain, which is posteriorly cleaved. The class II defensins have been described only in Solanaceae species, which indicated that this class is restricted to this family. In this work, a search by regular expression (RegEx) was applied to Arabidopsis thaliana proteome, a model plant with more than 300 predicted defensin genes. Two sequences were identified, A7REG2 and A7REG4, which have a typical plant defensin structure and an additional C-terminal prodomain. The evolutionary distance between Brassicaceae and Solanaceae and the presence class II defensin sequences in both families suggest that class II may be derived from a common eudicots ancestor. The discovery of class II defensins in other plants could shed some light in the plant physiology, as this class plays multiple roles in such context.