Suppression of OsVPE3 Enhances Salt Tolerance by Attenuating Vacuole Rupture during Programmed Cell Death and Affects Stomata Development in Rice

Background: Vacuolar processing enzymes (VPEs) are cysteine proteinases that act as crucial mediators of programmed cell death (PCD) in plants. In rice, however, the role of VPEs in abiotic stress-induced PCD remains largely unknown. In this study, we generated OsVPE3 overexpression and suppression transgenic lines to elucidate the function of this gene in rice. Results: Survival rate and chlorophyll retention analyses showed that suppression of OsVPE3 clearly enhanced salt stress tolerance in transgenic rice compared with wild type. Furthermore, fragmentation of genomic DNA was inhibited in plants with down-regulated OsVPE3. Vital staining studies indicated that vacuole rupture occurred prior to plasma membrane collapse during salt-induced PCD. Notably, overexpression of OsVPE3 promoted vacuole rupture, whereas suppression of OsVPE3 attenuated or delayed the disintegration of vacuolar membranes. Moreover, we found that suppression of OsVPE3 caused decreased leaf width and guard cell length in rice. Conclusions: Taken together, these results indicated that suppression of OsVPE3 enhances salt tolerance by attenuating vacuole rupture during PCD. Therefore, we concluded that OsVPE3 plays a crucial role in vacuole-mediated PCD and in stomatal development in rice.