Comparative analysis of osmotins from Tripogon loliiformis and Oryza sativa revealed role in abiotic stress tolerance through signalling pathways

T Le, B Williams and S Mundree

Centre for Tropical Crops and Biocommodities, Queensland University of Technology

Plant osmotins are a class of pathogen-related proteins that play key roles in both abiotic and biotic stress responses. However, the mechanisms underlying their functions in stress response are not well established due to the lack of information in their interaction partners and pathways. To understand the functions and stress-responsive pathways by which osmotins mediate plant response to stress, an osmotin from the native Australian resurrection grass Tripogon loliiformis (TlOsm) and two osmotins (OsOlp1_A and OsOlp1_I) from drought-tolerant (Apo) and -sensitive (IR64) cultivars of the stress sensitive crop, Oryza sativa (rice), were compared. Transgenic rice plants expressing the respective osmotins were assessed for enhanced drought tolerance. Additionally, each potential protein partners for each osmotin were assessed by Arabidopsis protein microarray (chip). Evaluation of the transgenic rice suggested functional roles for TlOsm and OsOlp1_A in enhancing drought tolerance with plants expressing TlOsm displaying the highest levels of tolerance. Upon protein array, 270 Arabidopsis proteins significantly interacted with the osmotins, 237 and 239 proteins interacted with OsOlp1_I and OsOlp1_A, while 268 proteins interacted with TlOsm. Interestingly, 11 proteins interacting with TlOsm and OsOlp1_A but not OsOlp1_I, and 21 proteins only interacting with TlOsm were found to be involved in diverse stress-responsive and signalling pathways. GO term enrichment and pathway analysis of osmotin interactors indicated the three most dominant pathways to be Fructose and Mannose metabolism, Glycolysis, and Pentose Phosphate pathway. The differential interactors of these osmotins provide the key mechanisms underlying the function of osmotins in plant stress responses.