Oryza sativa,C4HC3‐type really interesting new gene (RING),OsRFPv6, is a positive regulator in response to salt stress by regulating Na⁺absorption

Abstract

Salinity negatively affects plant growth, productivity, and metabolism. Therefore, plants have evolved diverse strategies to survive in saline environments. To identify such strategies involving the ubiquitin/26S proteasome system, we characterized molecular functions of a rice C4HC3 really interesting new gene (RING)-type E3-ubiquitin ligase gene. Oryza sativa RING finger protein v6 (OsRFPv6) was highly expressed under conditions of abiotic stress, induced by 100 mM NaCl and 20% PEG. The GFP-OsRFPv6 protein was localized in the plasma membrane and cytosol in rice protoplasts. In vitro ubiquitin assay revealed that OsRFPv6 possessed E3-ubiquitin ligase activity, but its variant OsRFPv6C100A did not.OsRFPv6-overexpressing plants were insensitive to salinity, but their growth was delayed under normal conditions. Under saline conditions, transgenic plants exhibited higher proline, soluble sugar, and chlorophyll content and lower H 2 O 2 accumulation than wild-type plants. Moreover, transgenic plants exhibited lower Na + uptake, lower Na + content, and higher K + content in the xylem sap assay. Under saline conditions, the expression levels of nine Na + /K + transporter genes in roots and leaves were significantly different between transgenic and wild-type plants. Specifically, under both normal and saline conditions, the expression of OsHKT2;1, a Na + transporter, in the roots of transgenic plants was lower than that in the roots of wild-type plants. These results suggest that OsRFPv6 E3-ubiquitin ligase serves as a positive regulator of salinity response via Na + uptake.

The Rice Abscisic Acid-Responsive RING Finger E3 Ligase OsRF1 Targets OsPP2C09 for Degradation and Confers Drought and Salinity Tolerance in Rice

“…In contrast to these diverse negative regulatory rice RING finger proteins, a few positive players were identified in the abiotic stress response of rice. The RING H2 type E3 ligase OsSIRH2-14 and C4HC3 RING E3 ligase OsRFPv6 enhanced salinity tolerance ( Park et al, 2019b ; Qin et al, 2020 ; Kim et al, 2021b ). In addition, the molecular function and targets of most rice RING finger proteins in growth and stress response still remain unknown.…”

“…2019b; Qin et al, 2020;Kim et al, 2021b). In addition, the molecular function and targets of most rice RING finger proteins in growth and stress response still remain unknown.…”

“…In rice, a number of RING finger proteins have been recently reported to play either negative or positive roles in the regulation of drought and salinity stress ( Gao et al, 2011 ; Ning et al, 2011 ; Hwang et al, 2016 ; Park et al, 2018 ; Park et al, 2019b ; Kim M.H. et al, 2020 ; Qin et al, 2020 ; Kim et al, 2021b ; Kim and Jang, 2021 ; Seo et al, 2021 ). So far, only a few protein targets of RING finger E3 ligases have been identified.…”

RING Zinc Finger Proteins in Plant Abiotic Stress Tolerance

“…Plant RING zinc finger proteins are located in the plasma membrane, cytoplasm, and nucleus. RING zinc finger proteins located in the plasma membrane with a characteristic transmembrane domain include ABA INSENSITIVE RING PROTEIN 1 (AtAIRP1) ( Ryu et al, 2010 ), RING-H2 FINGER A2A (RHA2a) ( Li H. et al, 2011 ), and ARABIDOPSIS TÓXICOS EN LEVADURA 78 (AtATL78) ( Kim S. J. and Kim W. T., 2013 ) in Arabidopsis; RING DOMAIN-CONTAINING PROTEINS 1 (OsRDCP1) ( Bae et al, 2011 ), SALT-INSENSITIVE RING H2-TYPE 14 (OsSIRH2-14) ( Park et al, 2019 ), and RING FINGER PROTEIN V6 (OsRFPv6) ( Kim et al, 2021 ) in rice; VpRH2 in grape ( Wang et al, 2017 ); LjCZF1 in Lotus japonicus ( Cai et al, 2018 ); and StRFP2 in potato ( Qi et al, 2020 ). Some of the transmembrane RING zinc finger proteins (such as AtATL78, RHA2a, OsRFPv6, and OsRDCP1) involved in abiotic stress are shown in Figure 1 .…”

“…OsSIRH2-14 may positively regulate the salt stress response by regulating the stability of salt-related proteins. Rice RING FINGER PROTEIN V6 (OsRFPv6) ( Kim et al, 2021 ) is a RING-HC-type zinc finger protein with E3 ubiquitin ligase activity that positively regulates salt tolerance in rice. OsRFPv6 was highly expressed under saline conditions.…”