Overexpression of a C3HC4-type RING E3 ligase gene, OsRFPHC-13, improves salinity resistance in rice, Oryza sativa, by altering the expression of Na<SUP>+</SUP>/K<SUP>+</SUP> transporter genes

초록

Salinity stress is a major restriction to increasing crop production. We characterized the Oryza sativa C3HC4-type RING E3 ligase-13 (OsRFPHC-13), which contributes a positive role in enhancing salinity insensitivity. Expres-sion of OsRFPHC-13 was highly induced by treatment with 100 mM NaCl, 20% PEG, or 100 mu M ABA. The OsRFPHC-13-GFP fusion protein was expressed in the chloroplasts and cytosol of the rice protoplasts. An in vitro ubiquitination assay confirmed that OsRFPHC-13 possesses E3 ligase activity; however, the mutation of OsRFPHC-13C232A did not show this activity. OsRFPHC-13-overexpressing plants showed a dwarf phenotype, short primary root length, and small lateral root number compared to WT and osrpfhc-13. In contrast, under salt stress, OsRFPHC-13-overexpressing plants showed enhanced salinity insensitivity by reducing the accumulation of Na+ in shoots and roots, increasing the activity of ROS scavenging, and positively regulating the expression of Na+/K+ transporter genes compared to WT and osrpfhc-13. In addition, OsRFPHC-13-overexpressing plants exhibited increased ABA sensitivity in the germination assay but decreased sensitivity in osrpfhc-13 compared to WT. These results suggest that OsRFPH-13 E3 ligase positively regulates the response to salinity via an ABA -dependent mechanism in rice.

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