Positive regulation of rice RING E3 ligase OsHIR1 in arsenic and cadmium uptakes

Abstract

The metalloid arsenic (As) and the heavy metal cadmium (Cd) are ubiquitously found at low concentrations in the earth. High concentrations of these elements in the soil and crops are severely dangerous to human health. We attempted to retrieve the RING E3 ubiquitin ligase gene for regulating As and Cd uptakes via the ubiquitin 26S proteasome system. Semi-quantitative reverse transcription polymerase chain reaction was conducted for a total of 47 Oryza sativa RING finger protein (OsRFP) genes to assess their expression patterns when exposed to As and Cd treatments. We identified one gene Oryza sativa heavy metal induced RING E3 ligase 1 (OsHIR1), which was significantly upregulated with both treatments. A yeast hybrid screen and a bimolecular fluorescence complementation assay showed that OsHIR1 clearly interacts with 5 substrate proteins, including tonoplast intrinsic protein 4;1 (OsTIP4;1) in the plasma membrane. In addition, OsHIR1 strongly degraded the protein level of OsTIP4;1 via the ubiquitin 26S proteasome system. Heterogeneous overexpression of OsHIR1 in Arabidopsis exhibited As- and Cd-insensitive phenotypes and resulted in decreased As and Cd accumulation in the shoots and roots, relative to the control. Herein, we report the novel finding that the OsHIR1 E3 ligase positively regulates OsTIP4;1 related to As and Cd uptakes.

Molecular characterization of rice arsenic‐induced RING finger E3 ligase 2 (OsAIR2) and its heterogeneous overexpression in Arabidopsis thaliana

“…Previously, we reported positive regulation of As and cadmium uptake in rice by RING E3 ligase (Lim et al ). Furthermore, it has been reported that heterologous overexpression of OsAIR1 positively regulates post germination plant growth under As(V) stress (Hwang et al ).…”

“…Therefore, our results may provide important clues to the mechanisms of posttranslational modifications in plants that have adapted to As exposure. Previously, we reported positive regulation of As and cadmium uptake in rice by RING E3 ligase (Lim et al 2014). Furthermore, it has been reported that heterologous overexpression of OsAIR1 positively regulates post germination plant growth under As(V) stress (Hwang et al 2016).…”

“…A couple of similar findings have been reported; for example, Hwang et al () reported that OsAIR1 ‐overexpressing plants showed changes in the proportion of seedlings with increases in cotyledon and root lengths during As treatment. Overexpression of another rice RING E3 ligase, OsHIR1 , yielded As‐insensitive phenotypes (Lim et al ). Taken together, our findings suggest that ubiquitin‐mediated degradation of OsAIR2 E3 ligase plays an important role in coping with As stress.…”

Ubiquitination pathway as a target to develop abiotic stress tolerance in rice

“…The OsHIR1 protein interacts with the OsTIP4;1 aquaporin, mediating its proteolysis through the ubiquitin/proteasome 26S degradation pathway. 31 Therefore, according to the authors, the OsHIR1 E3 ligase protein is able to control the absorption of these metals in the plant, probably through the OsTIP4;1 protein regulation via ubiquitination. Even though aquaporin proteins have not been described as As-transporter in plants until now, Zhao et al 32 stated that some TIP channels might be permeable to As transport into the vacuoles, due to its pore structure.…”

“…Moreover, OsHIR1 overexpression in Arabidopsis also increased the tolerance to As and Cd, when compared to wild-type plants. 31 It is important to highlight that definitive proof of involvement of OsTIP4;1 in As and Cd efflux transport to the vacuole would require the demonstration of its biochemical activity in vitro. Anyway, this was the first study to present an E3 ligase with RING domain conferring tolerance to metals in plants.…”