Blueberry VcLON 2, a peroxisomal LON protease, is involved in abiotic stress tolerance

Peroxisomal LON2 protease plays a pivotal role in protein quality control through its proteolysis and chaperone functions. However, little is known regarding its function in the regulation of cellular reactive oxygen species (ROS) homeostasis and in adversity tolerance in plants. To begin to assess the function of LON2, we isolated a VcLON2 cDNA from blueberry (Vaccinium corymbosum L.), which is predicted to encode a peroxisomal protein containing a long N-terminal domain, a central AAA+ module and a C-terminal proteolytic domain. Quantitative real-time RT-PCR analysis revealed that VcLON2 was expressed ubiquitously throughout the blueberry plant including vegetative and reproductive organs, and its expression increased in older tissues. Overexpression of VcLON2 in tobacco led to increased tolerance to NaCl, PEG and heat stresses, as indicated by the lower contents of H2O2, malondialdehyde (MDA) and carbonyl groups, compared with wild type (WT). In contrast, silencing of the VcLON2 homolog, NbLON2, in tobacco seedlings resulted in significantly higher sensitivity to various abiotic stresses. Furthermore, the activity of catalase (CAT), a peroxisomal enzyme involved in the detoxification of ROS, was found to be elevated in VcLON2-overexpressed seedlings and conversely reduced in NbLON2-silenced seedlings under non-stress and stress conditions, compared with WT. Our results suggest that VcLON2 plays an important role in the maintenance of the ROS-scavenging functions of peroxisomes, which is necessary for tolerance to abiotic stresses.