Unexpected Response of Pea Roots to the Salicylic Acid: Induction of Chitinase-Like Proteins Compared to Chitinases

Chitinases and chitinase-like proteins (CLP) widely represented in the plants. CLPs share significant sequence and structure similarity with active chitinases, but not display chitinase activity. The role of chitinases—as chitin degrading enzymes well studied, whereas function of CLP is mainly elusive. In the Pisum sativum L. roots’ salicylate-induced CLP (PsCLP) were identified using a combination of proteomic and transcriptomic techniques. Seven similar sequences of the PsCLPs in the pea genome were revealed. The use of bioinformatic methods of analysis made it possible to characterize revealed proteins. Analysis of the structure and domain organization of the PsCLPs showed the amino acid substitutions in the catalytically important DxDxE motif. Detected SA-induced proteins do not display chitinase activity toward to glycol chitin. The expression of revealed PsCLP genes significantly upregulates after 12 h and decreases after 72 h of SA action. It has been shown that identified proteins are secreted into the apoplast. Comparison of the expression level of PsCLPs and active chitinases under the action of SA showed that it is the former that are induced to a greater extent. Induction of inactive PsCLPs in roots, as compared to the induction of active direct-acting antipathogenic proteins indicates a different defense strategy implemented in the roots of some legumes.