Knock-down of stress inducible OsSRFP1 encoding an E3 ubiquitin ligase with transcriptional activation activity confers abiotic stress tolerance through enhancing antioxidant protection in rice

Abstract

E3 ubiquitin ligases are involved in a variety of physiological processes. This study demonstrated the function of a previously unknown rice RING finger E3 ligase, Oryza sativa Stress-related RING Finger Protein 1 (OsSRFP1) in stress responses in rice. OsSRFP1 was ubiquitously expressed in various rice organs, with the higher expression levels in roots, panicles and culm nodes. The transcript of OsSRFP1 was induced by cold, dehydration, salt, H2O2 and abscisic acid treatments. Interestingly, the OsSRFP1-overexpressing plants were less tolerant to salt, cold and oxidative stresses than wild type plants; while the RNA interference silencing of OsSRFP1 plants were more tolerant than wild type without yield penalty. Compared with the wild type, amounts of free proline and activities of antioxidant enzymes were increased in the RNAi plants but decreased in the overexpression plants under cold stress, which were inversely correlated with the malondialdehyde and hydrogen peroxide (H2O2) levels in the tested lines. Microarray analysis showed that expression of numerous genes involving in ROS homeostasis was altered in the OsSRFP1-overexpressing plants under normal and cold conditions. In vitro ubiquitination assays showed that OsSRFP1 possessed E3 ubiquitin ligase activity and the intact RING domain was essential for the activity. Moreover, OsSRFP1 might function in transcriptional regulation with nuclear localization. Taken together, our results demonstrate that OsSRFP1 may have dual functions in post-translational and transcriptional regulations in modulating abiotic stress responses in rice, at least in part, by negatively regulating antioxidant enzymes-mediated reactive oxygen species removal.

Knock-down of a RING finger gene confers cold tolerance

“…Overall, under normal growth conditions, activities of POD (Peroxidase), T-SOD (Total Superoxide dismutase), and CAT (Catalase) were comparable between wild type and OsSRFP1-RNAi plants. There were marked increases in activities of these enzymes for the rice seedlings upon exposure to cold stress 1 . The cold stress-induced increases in activities of POD, T-SOD, and CT were higher in the OsSRFP1-RNAi plants than in wild type plants.…”

“…The expression of endogenous OsSRFP1 was found to be induced by salt, drought, cold, H 2 O 2 , and abscisic acid treatments. OsSRFP1 is ubiquitously expressed in various rice tissues, with the higher expression levels in roots, panicles and culm nodes 1 . The constitutive expression of OsSRFP1 seems to be essential for plant growth and development under normal growth conditions through maintaining the low levels of the proteins affecting plant growth.…”

“…The increased cold tolerance of transgenic plants was linked to higher amounts of free proline and lower levels of electrolyte leakage in OsSRFP1 knock-down transgenic plants, suggesting that silencing of OsSRFP1 maintains the stability of membrane systems, which is the typical index of cold tolerance. Moreover, it was found that the antioxidant system was more efficient in RNAi plants and this could be the foundation of the improved cold tolerance as many genes involved in antioxidative responses were observed by microarray analysis 1 . The changes of gene expression may result in the changes in protein expression and activity.…”

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

“…Therefore, OsSRFP1 expression plays a negative role in the response to abiotic stresses in rice. 43 It was shown that decreased OsSRFP1 expression through RNAi makes silenced plants more tolerant to abiotic stresses than wild-type plants. 43 Silencing this gene increases SOD and CAT activity, intensifying the elimination of ROS and the tolerance to different stresses.…”

“…43 It was shown that decreased OsSRFP1 expression through RNAi makes silenced plants more tolerant to abiotic stresses than wild-type plants. 43 Silencing this gene increases SOD and CAT activity, intensifying the elimination of ROS and the tolerance to different stresses. It was also verified that silencing OsSRFP1 has led to a higher accumulation of free proline when rice plants are under low temperatures, which supports cell osmoregulation.…”