Osmotinlike

Osmotin-like proteins (OLPs) are a class of plant proteins related to osmotin, belonging to the thaumatin-like protein (TLP) family, also known as pathogenesis-related protein family 5 (PR-5). They are secreted extracellular proteins typically expressed in response to osmotic stress, salinity, drought, and pathogen attack. OLPs are characterized by a thaumatin-like domain and a cysteine-rich, disulfide-stabilized structure, and many possess an N-terminal signal peptide guiding secretion.

OLPs are synthesized with a signal peptide and are transported through the secretory pathway to accumulate in the apoplast or extracellular space. They are commonly about 180–210 amino acids long in their mature form and contain conserved cysteine residues that form disulfide bonds, contributing to stability under stress conditions. Some are glycosylated.

Functional studies show that osmotin and related proteins have antifungal activity in vitro against a range of plant pathogens and are induced by osmotic and drought stress as well as biotic challenges. The exact mechanisms are not fully resolved, but proposed modes include interaction with fungal membranes, perturbation of cellular homeostasis, and participation in defense signaling pathways that regulate plant responses to stress.

In biotechnology and crop science, osmotin-like proteins have been explored for improving disease resistance and stress tolerance. Transgenic expression of osmotin or osmotin-like genes in several crops has yielded enhanced resistance to fungal pathogens and, in some cases, improved tolerance to salt and drought conditions.