PATHOGENESIS-RELATED PROTEINS IN PLANTS: MOLECULAR FEATURES, FUNCTIONAL DIVERSITY, AND BIOTECHNOLOGICAL APPLICATIONS

Pathogenesis-related (PR) proteins are critical components of the plant immune system, rapidly accumulating in response to pathogen attack and various stresses. Since their first identification in tobacco infected with Tobacco Mosaic Virus (TMV), these inducible proteins have been classified into multiple families based on sequence and functional characteristics. PR proteins exhibit a range of biochemical activities – including cell-wall degrading enzyme activities (e.g., chitinases, glucanases), antimicrobial peptide functions (e.g., defensins, thionins), and protease inhibition – that contribute to direct pathogen suppression and modulation of defense signaling. Advances in molecular cloning have enabled transgenic expression of PR genes in susceptible crops, often leading to enhanced resistance against fungi, bacteria, oomycetes, and viruses. Beyond plant immunity, some PR proteins display multifunctional properties relevant to stress tolerance and pharmacology. This review summarizes current understanding of PR protein classification, molecular features, induction by biotic/abiotic cues, and their application in crop protection, while highlighting opportunities and challenges in harnessing PR proteins for biotechnology.