The rice gene Os02g0823100 was reported as RWC3 in 2004.
- Os02g0823100 <=> OsPIP1;3. PIP1.3, PIP1-3, RWC3, RWC-3, OsPIP1-3
- RWC3 was a water channel protein that facilitated water flux across membranes. It probably played a role in drought avoidance in rice.
- Gibberellin (GA) enhanced the GUS activity in the transgenic calli, suspension cells and leaves, whereas ancymidol (anc), an inhibitor of GA synthesis, reduced the GUS activity. Sucrose was found to inhibit the effects induced by addition of GA, suggesting a possible cross-talk between GA and sucrose signaling on regulation of the RWC3 gene expression.
- The PCR was performed with the Pfu high fidelity Taq DNA polymerase so that a blunt-ended product was obtained and cloned into SmaI site of the pCAMBIA1381Z vector (Fig.1), forming the RWC3 promoter guided GUS report gene expression construct. The RWC3 promoter was thereafter cloned into the pCAMBIA1381Z vector, and its orientation was verified by sequencing and restricted enzyme cutting.
- wild-type and trangentic plants:
- Compared to the wild-type plant, the transgenic lowland rice exhibited higher root osmotic hydraulic conductivity (Lp), leaf water potential and relative cumulative transpiration at the end of 10 h PEG treatment.
- The transgenic plants had approximately the equivalent amount of RWC3 mRNA or protein under non-stress conditions, while they had a clearly increased RWC3 amount compared with the wild-type plants under the water deficit. The up-regulation of RWC3 in these transgenic plants was dependent on water deficit condition.
- However, no observable phenotypic difference was found between the transgenic plants and the wild-type plants, either under non-stress or during water deficit.
- In the transgenic rice root, GUS activity was shown in elongation and mature zones, and was very significant in cells adjacent to the vascular bundles, in exodermis and root hairs.
- In the leaves, GUS activity was found not only in leaf vascular bundles, but also in mesophyll cells, and the expression in the cells around vascular bundles appeared to be higher than inmesophyll cells. High GUS activity was also observed in stem tissue.
- The expression of water channel protein RWC3 mRNA was increased in upland rice at the early response (up to 4 h) to the 20% polyethylene glycol (PEG) 6000 treatment, whereas there was no significant expression changes in lowland rice. Protein levels were increased in upland rice and decreased in lowland rice at 10 h after the water deficit.
- The up-regulation of RWC3 in upland rice fits well with the knowledge that upland rice adopts the mechanism of drought avoidance. The physiological significance of this RWC3 up-regulation was then explored with the overexpression of RWC3 in transgenic lowland rice controlled by a stressinducible SWPA2 promoter.
- Overexpression of RWC3 enhanced the root osmotic Lp and improved water status during water deficit. Expression of RWC3 protein, as indicated by GUS staining intensity, was obviously high in immature embryo and the seed coat, and GUS activity in seed coats could be detected even after the endosperm wasmature.
- The media inhibited the effect of GA on the expression of RWC3.
- Presence of sucrose repressed the RWC3 expression, while incubation of the cells with the same concentration of mannitol for 48 h, which caused unfavorable growth conditions of the cells, stimulated the protein expression. The presence of GA ciselement in the promoter region of RWC3 suggest a signaling of GA involving such stimulation of the RWC3 expression, besides the water deficit-stimulated mechanism.
Sugars somehow affect pZSS4 and RWC3 transcription. A plausible mechanism is the triggering of starch digestion by sugar deprivation or low sugar concentration. Endogenous GA levels would rise during this starch digestion, which promoting RWC3 transcription in addition. Sugar levels may play a similar role in the aquapor in induction system.
Labs working on this gene
- Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai, 200032, P. R. China
- College of Education, Shanghai Normal University
- Laboratory of Plant Genetic Engineering, Biotechnology Institute, Akita Prefectural University, Ogata, Akita, Japan
- Plant Cell Biotechnology Laboratory, Korea Research Institute of Bioscience and Biotechnology, Oun-dong 52, Yusong, Taejon, 305-333 Korea
- Lian HL, Yu X, Ye Q, Ding X, Kitagawa Y, Kwak SS, Su WA, Tang ZC. The role of aquaporin RWC3 in drought avoidance in rice. Plant Cell Physiol. 2004 Apr;45(4):481-9. Erratum in: Plant Cell Physiol. 2004 Jun;45(6):810. Ding Xiao-Song [corrected to Ding Xiaodong]. PubMed PMID: 15111723.