Homologous U-box E3 Ubiquitin Ligases OsPUB2 and OsPUB3 Are Involved in the Positive Regulation of Low Temperature Stress Response in Rice (Oryza sativa L.)

Abstract

Rice U-box E3 Ub ligases (OsPUBs) are implicated in biotic stress responses. However, their cellular roles in response to abiotic stress are poorly understood. In this study, we performed functional analyses of two homologous OsPUB2 and OsPUB3 in response to cold stress (4°C). OsPUB2 was up-regulated by high salinity, drought, and cold, whereas OsPUB3 was constitutively expressed. A subcellular localization assay revealed that OsPUB2 and OsPUB3 were localized to the exocyst positive organelle (EXPO)-like punctate structures. OsPUB2 was also localized to the nuclei. OsPUB2 and OsPUB3 formed a hetero-dimeric complex as well as homo-dimers in yeast cells and in vitro. OsPUB2/OsPUB3 exhibited self-ubiquitination activities in vitro and were rapidly degraded in the cell-free extracts with apparent half-lives of 150–160 min. This rapid degradation of OsPUB2/OsPUB3 was delayed in the presence of the crude extracts of cold-treated seedlings (apparent half-lives of 200–280 min). Moreover, a hetero-dimeric form of OsPUB2/OsPUB3 was more stable than the homo-dimers. These results suggested that OsPUB2 and OsPUB3 function coordinately in response to cold stress. OsPUB2- and OsPUB3-overexpressing transgenic rice plants showed markedly better tolerance to cold stress than did the wild-type plants in terms of survival rates, chlorophyll content, ion leakage, and expression levels of cold stress-inducible marker genes. Taken together, these results suggested that the two homologous rice U-box E3 Ub ligases OsPUB2 and OsPUB3 are positive regulators of the response to cold stress.

Coordination of light, circadian clock with temperature: The potential mechanisms regulating chilling tolerance in rice

“…In rice, STRESS‐RELATED RING FINGER PROTEIN1 ( OsSRFP1 ) encoding a RING finger E3 ligase, is induced by chilling stress but acts as a negative regulator of chilling tolerance, at least in part, by negatively regulating antioxidant enzymes‐mediated ROS removal (Fang et al 2015). Rice U‐box E3 Ub ligases OsPUB2 and OsPUB3 were demonstrated to be positive regulators of rice chilling tolerance (Byun et al 2017). The hetero‐dimeric complex OsPUB2/OsPUB3 exhibited self‐ubiquitination activities and degraded rapidly in cell‐free extract (Byun et al 2017).…”

“…Rice U‐box E3 Ub ligases OsPUB2 and OsPUB3 were demonstrated to be positive regulators of rice chilling tolerance (Byun et al 2017). The hetero‐dimeric complex OsPUB2/OsPUB3 exhibited self‐ubiquitination activities and degraded rapidly in cell‐free extract (Byun et al 2017). Interestingly, degradation was delayed in the presence of the crude extracts of cold‐treated seedlings, implying key roles of E3 ligases in chilling response of rice (Byun et al 2017).…”

Transcriptome profiling and phytohormone responses of Arabidopsis roots to different ambient temperatures

“…Ubiquitylation and proteasome-mediated ubiquitin-dependent protein catabolic processes are required for protein ubiquitination and degradation (Callis and Vierstra 2000). Previous work found that U-box E3 ubiquitin ligases AtCHIP and PLANT U-BOXs (PUBs) are involved in temperature stress tolerance and the AtCHIP transcript was upregulated by high temperature (Yan et al 2003;Cho et al 2006;Min et al 2016;Byun et al 2017). We found that elevated ambient temperature had the same effect on AtCHIP (AT3G07370) expression, and that genes encoding RING/U-box superfamily proteins involved in protein ubiquitination (e.g.…”

Cold tolerance in rice plants is partially controlled by root responses

“…Rice ( Oryza sativa L.) is one of the most important cereal crops, providing food for more than half of the world’s population (Zhang et al 2017). Rice production can be seriously affected by environmental stresses, including low temperature, since it is normally grown in tropical and temperate climate zones, and therefore is sensitive to chilling (Mukhopadhyay et al 2004; Byun et al 2017). Cold can be harmful from germination to reproductive stages, in most cases resulting in decreased crop yield (Ma et al 2009; Cruz et al 2013).…”

“…Given its tropical origin, cultivated rice germplasm genetic variability is very limited to identify cold stress tolerance genes and alleles (Byun et al 2017). A few examples of alleles associated with low temperature tolerance are derived from japonica subspecies, as COLD1 jap and bZIP73 jap (Ma et al 2015; Liu et al 2018).…”