The SUV3 (suppressor of Var 3) gene encodes a DNA and RNA helicase, which is localized in mitochondria and is a subunit of the degradosome complex involved in regulation of RNA surveillance and turnover.
- OsSUV3 protein exhibits DNA and RNA helicase, and ATPase activities. It also contains the characteristic DNA and RNA helicase activity. OsSUV3 can use mainly ATP or dATP as energy source for the unwinding activity and it cannot unwind the blunt-end duplex DNA substrate. OsSUV3 unwinds DNA in both the 5’-3’ and 3’-5 directions and thus its activity is bipolar in vitro. The Km values of OsSUV3 are 0.51 nM and 0.95 nM for DNA helicase and RNA helicase, respectively.
- OsSUV3 is induced in rice seedlings in response to high levels of salt. The possible mechanism could be that OsSUV3 helicase functions in salinity stress tolerance by improving photosynthesis and antioxidant machinery in transgenic rice. OsSUV3 interacts with a variety of different proteins, such as exoribonuclease, exonuclease, endonuclease, some splicing factors, and a few RNA and DNA helicases. OsSUV3 functions in cadmium and zinc stress tolerance in rice. In response to cadmium and zinc stress the OsSUV3 transcript level is induced in rice and its overexpression in transgenic IR64 rice plants confers the metal stress tolerance.
- The unique properties of OsSUV3 including its dual helicase activity imply that it could be a multifunctional protein involved in biologically significant process of DNA and RNA metabolisms. OsSUV3 protein contains bidirectional DNA unwinding activity. OsSUV3 is most likely a multifunctional protein involved in diverse processes including nucleic acid metabolism and might be playing important roles in numerous physiological processes in plant. In response to stress, OsSUV3 rice plants maintained plant hormone levels that regulate the expression of several stress-induced genes and reduce adverse effects of salt on plant growth and development and therefore sustains crop productivity.
- SUV3 overexpressing salt tolerant transgenic rice evaluated in New Delhi and Cuttack soil conditions for their effects on physicochemical and biological properties of rhizosphere. Its cultivation does not affect soil properties viz., pH, Eh, organic C, P, K, N, Ca, Mg, S, Na and Fe2+. Additionally, SUV3 rice plants do not cause any change in the phenotype, species characteristics and antibiotic sensitivity of rhizospheric bacteria. The population and/or number of soil organisms such as bacteria, fungi and nematodes were unchanged in the soil.
- Also, the activity of bacterial enzymes viz., dehydrogenase, invertase, phenol oxidases, acid phosphatases, ureases and proteases was not significantly affected. Further, plant growth promotion (PGP) functions of bacteria. The present findings suggest ecologically pertinent of salt tolerant SUV3 rice to sustain the health and usual functions of the rhizospheric organisms.
- Three transgenic lines:
- VC(vector control)
- The T1 and T2 sense transgenic lines showed tolerance to high salinity and fully matured without any loss in yields. The T2 transgenic lines also showed tolerance to drought stress. the introduced trait is functional and stable in transgenic rice plants. The rice OsSUV3 sense transgenic lines showed lesser lipid peroxidation, electrolyte leakage and H2O2 production, along with higher activities of antioxidant enzymes under salinity stress, as compared with wild type, vector control and antisense transgenic lines, which suggesting that the existence of an efficient antioxidant defence system to cope with salinity-induced oxidative damage.
- OsSUV3 T1 sense transgenic rice plants accumulate less MDA, H2O2 and ion leakage, and show better antioxidant response. Seeds of T2 sense transgenic plants showed good postgermination growth under drought stress conditions, whereas WT seeds failed to germinate under the same conditions. There was no germination in T2 transgenics and WT seeds at 4°C, for up to 14 days (Figure 6b).
- Seeds of T2 sense transgenic plants (L1-L3) showed good post-germination growth under 200μM CdCl2 and 300 μM ZnCl2 stress while WT, AS and VC seeds showed much lesser germination under same conditions (Fig. 1F and G).
- The transgenic OsSUV3 overexpressing rice T1 lines showed significantly higher endogenous content of plant hormones viz., gibberellic acid (GA3), zeatin (Z) and indole-3-acetic acid (IAA) in leaf, stem and root as compared to wild-type (WT), vector control (VC) and antisense (AS) plants under salt (200 mM NaCl) stress condition. A similar trend of endogenous plant hormones profile was also reflected in the T2 generation of OsSUV3 transgenic rice under defined parameters and stress condition.
- Quantitative RT-PCR analyses of OsSUV3 under different abiotic stress conditions:
- The salt treatment of IR64 rice seedlings showed a significant increase in the transcript level of OsSUV3. The 200–mM NaCl treatment induced a roughly fivefold increase in expression of OsSUV3 during the first hour (1 h), and this transcript accumulation gradually increased until 12 h (approximately 13-fold; Figure 2a). It appears as an early as well as prolonged and strong response against NaCl exposure.
- As compared with the NaCl, the WT plants accumulated lesser transcripts of OsSUV3 when subjected to KCl treatment (Figure 2b). The maximum expression of OsSUV3 was five-fold after treatment with KCl (Figure 2b), as opposed to a 13–fold increase after NaCl treatment.
- The heat stress upregulated the OsSUV3 transcript level to a lesser extent (threefold at 2 and 12 h), as compared with the NaCl treatment (Figure 2c).
- ABA treatment induced OsSUV3 with a sixfold increase in expression during the early period (2 h; Figure 2d).
- Its expression, driven by a constitutive cauliflower mosaic virus 35S promoter in IR64 transgenic rice plants, confers salinity tolerance.
- The expression of OsSUV3 transcript was upregulated in the presence of cadmium and zinc in rice seedlings, which suggesting that OsSUV3 is involved in maintaining the homeostasis of these ions. Enhanced expression of OsSUV3 with respect to the metals stress suggests that it might be regulated through Cd2+ and Zn2+ dependent signal transduction pathways.
- OsSUV3 encodes an NTP-dependent RNA/DNA helicase, which is related to the DExH/D (Ski2p) superfamily.
- OsSUV3 demonstrates approximately 32–61% identity with its counterparts from S. cerevisiae, H. sapiens and A. thaliana. OsSUV3 contains all the characteristic conserved helicase motifs from I, Ia, Ib, II, III, IV, V and VI, both OsSUV3 and AtSUV3 contain two distinct domains: a helicase ATP-binding domain and a helicase C–terminal domain. The model that was built using H. sapiens SUV3 as the template was studied in detail. OsSUV3 primary sequence residues 59–541 showed approximately 40% sequence identity with the SUV3 helicase from H. sapiens.
- Many genes including helicases are known to be involved in abiotic stress tolerance. Helicases are ubiquitous enzymes that catalyse the unwinding of energetically stable duplex DNA or RNA secondary structures, and thereby play an important role in almost all DNA and/or RNA metabolic processes.
- The product of the SUV3 gene was first described in yeast Saccharomyces cerevisiae.The human nuclear SUV gene (SUPV3L1) encodes an NTP-dependent RNA/DNA helicase (SUV3p, hSUV3p), which is related to the DexH/D (Ski2p) super family. The gene has been conserved during evolution and is present in purple bacteria, plants, C. elegans, Drosophila, mammals and in all eukaryotes.
Labs working on this gene
- International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India
- Tuteja N, Sahoo R K, Garg B, et al. OsSUV3 dual helicase functions in salinity stress tolerance by maintaining photosynthesis and antioxidant machinery in rice (Oryza sativa L. cv. IR64)[J]. The Plant Journal, 2013, 76(1): 115-127.
- Sahoo R, Tuteja N. OsSUV3 functions in cadmium and zinc stress tolerance in rice (Oryza sativa L. cv IR64)[J]. Plant signaling & behavior, 2014, 9(1): e27389.
- Sahoo R K, Ansari M W, Tuteja R, et al. OsSUV3 transgenic rice maintains higher endogenous levels of plant hormones that mitigates adverse effects of salinity and sustains crop productivity[J]. Rice, 2014, 7(1): 17.
- Tuteja N, Tarique M, Tuteja R. Rice SUV3 is a bidirectional helicase that binds both DNA and RNA[J]. BMC plant biology, 2014, 14(1): 283.
- Sahoo R K, Ansari M W, Tuteja R, et al. Salt tolerant SUV3 overexpressing transgenic rice plants conserve physicochemical properties and microbial communities of rhizosphere[J]. Chemosphere, 2015, 119: 1040-1047.
- Jedrzejczak R, Wang J, Dauter M, et al. Human Suv3 protein reveals unique features among SF2 helicases[J]. Acta Crystallographica Section D: Biological Crystallography, 2011, 67(11): 988-996.
- Tuteja N. Plant DNA helicases: the long unwinding road*[J]. Journal of experimental botany, 2003, 54(391): 2201-2214.
- Tuteja N. Mechanisms of high salinity tolerance in plants[J]. Methods in enzymology, 2007, 428: 419-438.
- Stepien P P, Margossian S P, Landsman D, et al. The yeast nuclear gene suv3 affecting mitochondrial post-transcriptional processes encodes a putative ATP-dependent RNA helicase[J]. Proceedings of the National Academy of Sciences, 1992, 89(15): 6813-6817.
- Dmochowska A, Kalita K, Krawczyk M, et al. A human putative Suv3-like RNA helicase is conserved between Rhodobacter and all eukaryotes[J]. Acta biochimica Polonica, 1998, 46(1): 155-162.