Oryza sativa salt-induced RING E3 ligase 2 (OsSIRP2) acts as a positive regulator of transketolase in plant response to salinity and osmotic stress

Abstract

A rice gene (OsSIRP2) encoding the RING Ub E3 ligase was highly induced under salinity stress and physically interacted with a transketolase (OsTKL1). Overexpression of OsSIRP2 conferred salinity and osmotic stress tolerance in plants. The RING E3 ligases play a vital role in post transitional modification through ubiquitination-mediated protein degradation that mediate plants responses during abiotic stresses and signal transduction. In this study, we report an Oryza sativa salt induced Really Interesting New Gene (RING) finger protein 2 gene (OsSIRP2) and elucidate its role under salinity and osmotic stress. The transcript levels of OsSIRP2 in rice leaves were induced in response to different abiotic stresses, such as salt, drought, heat, and abscisic acid (ABA) exposure. In vitro ubiquitination revealed that the OsSIRP2 protein formed poly-ubiquitin products, whereas a single amino acid substitution in OsSIRP2 (OsSIRP2) in the RING domain did not form ubiquitinated substrates, supporting the hypothesis that E3 ligase activity requires the functional RING domain. Using the yeast two-hybrid (Y2H) assay, O. sativa transketolase 1 (OsTKL1) was identified as an interacting partner. OsSIRP2 was localized in the nucleus, whereas its interacting partner (OsTKL1) was localized in the cytosol and plastids in the rice protoplasts. Fluorescence signals between OsSIRP2 and OsTKL1 were observed in the cytosol. The pull-down assay confirmed the physical interaction between OsSIRP2 and OsTKL1. In vitro ubiquitination assay and in vitro protein degradation assay revealed that OsSIRP2 ubiquitinates OsTKL1 and enhances the degradation of OsTKL1 through the 26S proteasomal pathway. Heterogeneous overexpression of OsSIRP2 resulted in conferring tolerance against salinity and osmotic stress. Overall, our findings suggest that OsSIRP2 may be associated with plant responses to abiotic stresses and act as a positive regulator of salt and osmotic stress tolerance.

Plant E3 Ligases and Their Role in Abiotic Stress Response

“…Rice expresses many RING finger E3 ligases that are involved in salt stress regulation, such as the SALT-INDUCED RING PROTEIN family (SIRP) [ 123 , 124 , 125 , 126 ] ( Figure 4 ). Three of the four members have been described as negative regulators of salinity stress responses [ 123 ].…”

“…On the other hand, overexpression of OsSIRP2 E3 ligase enhances resistance towards salt and osmotic stress in Arabidopsis [ 124 ]. Yeast two-hybrid (Y2H) and pulldown assays have demonstrated physical interaction between OsSIRP2 and a potential target, O. sativa TRANSKETOLASE 1 (OsTKL 1 ) [ 124 ].…”

Overexpression of tomato RING E3 ubiquitin ligase gene SlRING1 confers cadmium tolerance by attenuating cadmium accumulation and oxidative stress

“…A total of 474 RING domains have been identified in 469 potential proteins encoded in the tomato ( Solanum lycopersicum ) genome (Yang et al, 2019). However, the functional studies of RING E3 ubiquitin ligase genes in tomato are very limited (Chapagain et al, 2018; Cho et al, 2017; Kim et al, 2019; Qi et al, 2020; Yang et al, 2019). Previously, we screened out a tomato RING‐type E3 ubiquitin ligase gene, SlRING1 , which was highly expressed in tomato roots in response to Cd stress (Qi et al, 2020).…”

Modulation of Abiotic Stress Responses in Rice by E3-Ubiquitin Ligases: A Promising Way to Develop Stress-Tolerant Crops

“…Oryza sativa salt-induced RING finger protein 2 (OsSIRP2) is induced by high salinity, drought, and ABA and encodes a RING-type E3-ubiquitin ligase that localizes to the nucleus of rice protoplasts under both control and high-salinity conditions. OsSIRP2, when overexpressed in Arabidopsis, is shown to confer tolerance to salinity and osmotic stresses (Chapagain et al, 2018). It is also shown that OsSIRP2 is able to interact with the rice transketolase 1 (OsTKL1) in the cytoplasm, targeting it for degradation via the UPS.…”