PUB63, a novel early heat responsive ubiquitin E3 ligase from rice implicates heat stress tolerance

Heat stress has emerged as a major environmental challenge triggering reduced crop yields, compromised growth, and negatively affecting the development of crops. The cellular response to heat stress involves transcriptional and translational reprogramming and regulation of protein homeostasis which is crucial for the heat stress response and leads to the differential expression of many genes associated with protein turnover mechanisms. Plant U-box (PUB) proteins are a class of the Ubiquitin-E3 ligase involved in the Ubiquitin-proteasome pathway. In the present study, we investigated the role of a PUB protein from rice, OsPUB63, involved in heat stress responses in rice. We also identified all PUB coding genes from O. sativa indica and compared with O. sativa japonica. A quantitative real time PCR demonstrated, OsPUB63 as an early heat inducible gene in rice and the subcellular localization study confirmed its presence in the nucleus and cytosol. OsPUB63 was demonstrated as a TPR repeat containing protein with molecular weight of 39.3 KDa. Using a combination of genetic, biochemical, and physiological assays, our work establishes OsPUB63 as crucial in regulating the heat stress response in rice. Specifically, we show that OsPUB63 enhances the heat stress tolerance in transgenic Arabidopsis by promoting the accumulation of proline and reduced MDA content. Our work has identified PUB63 as the first PUB gene family E3 ligase from rice which is implicated in heat stress response and provide a crucial target for improving crop yields under high-temperature conditions in rice.