SCARECROW promoter-driven expression of a bacterial mercury transporter MerC in root endodermal cells enhances mercury accumulation in Arabidopsis shoots
Mercury accumulation in Arabidopsis shoots is accelerated by endodermis specific expression of fusion proteins of a bacterial mercury transporter MerC and a plant SNARE SYP121 under control of SCARECROW promoter.
We previously demonstrated that the CaMV 35S RNA promoter (p35S)-driven ubiquitous expression of a bacterial mercury transporter MerC, fused with SYP121, an Arabidopsis SNARE protein increases mercury accumulation of Arabidopsis. To establish an improved fine-tuned mercury transport system in plants for phytoremediation, the present study generated and characterized transgenic Arabidopsis plants expressing MerC-SYP121 specifically in the root endodermis, which is a crucial cell type for root element uptake. We generated four independent transgenic Arabidopsis lines expressing a transgene encoding mCherry-MerC-SYP121 under the control of the endodermis-specific SCARECROW promoter (hereafter pSCR lines). Quantitative real-time PCR analysis showed that expression levels of the transgene in roots of the pSCR lines were 3–23% of the p35S driven-overexpressing line. Confocal microscopy analysis showed that mCherry-MerC-SYP121 was dominantly expressed in the endodermis of the meristematic zone as well as in the mature zone of the pSCR roots. Mercury accumulation in shoots of the pSCR lines exposed to inorganic mercury was overall higher than the wild-type and comparable to the p35S over-expressing line. These results suggest that endodermis-specific expression of the MerC-SYP121 fusion proteins in plant roots sufficiently enhances mercury uptake and accumulation into shoots, which would be an ideal phenotype for phytoremediation of mercury-contaminated environments.
KeywordsBacterial mercury transporter Cell-type specificity Endodermis MerC Phytoremediation SCARECROW
Soluble N-ethylmaleimide-sensitive factor protein attachment protein receptor
We thank Prof. Dr. Angelika Mustroph (University of Bayreuth) for providing a plasmid containing the pSCR fragment. This work was partly supported by the Japan Society for the Promotion of Science (Grant nos. 15H02839 and 18H03401 to M.K.).
- Castilhos Z, Rodrigues-Filho S, Cesar R, Rodrigues A, Villas-Bôas R, de Jesus I, Lima M, Faial K, Miranda A, Brabo E, Beinhoff C, Santos E (2015) Human exposure and risk assessment associated with mercury contamination in artisanal gold mining areas in the Brazilian Amazon. Environ Sci Pollut Res 22:11255–11264CrossRefGoogle Scholar
- Hachez C, Laloux T, Reinhardt H, Cavez D, Degand H, Grefen C, Rycke R, Inzé D, Blatt MR, Russinova E, Chaumont F (2014) Arabidopsis SNAREs SYP61 and SYP121 coordinate the trafficking of plasma membrane aquaporin PIP2;7 to modulate the cell membrane water permeability. Plant Cell 26:3132–3147CrossRefGoogle Scholar
- Liebert CA, Hall RM, Summers AO (1999) Transposon Tn21, flagship of the floating genome. Microbiol Mol Biol Rev 63:507–522Google Scholar
- Marquès-Bueno MD, Morao AK, Cayrel A, Platre MP, Barberon M, Caillieux E, Colot V, Jaillais Y, Roudier F, Vert G (2016) A versatile multisite gateway-compatible promoter and transgenic line collection for cell type-specific functional genomics in Arabidopsis. Plant J 85:320–333CrossRefGoogle Scholar
- Nakagawa T, Suzuki T, Murata S, Nakamura S, Hino T, Maeo K, Tabata R, Kawai T, Tanaka K, Niwa Y, Watanabe Y, Nakamura K, Kimura T, Ishiguro S (2007) Improved gateway binary vectors: high-performance vectors for creation of fusion constructs in transgenic analysis of plants. Biosci Biotechnol Biochem 71:2095–2100CrossRefGoogle Scholar
- Uraguchi S, Tanaka N, Hofmann C, Abiko K, Ohkama-Ohtsu N, Weber M, Kamiya T, Sone Y, Nakamura R, Takanezawa Y, Kiyono M, Fujiwara T, Clemens S (2017) Phytochelatin synthase has contrasting effects on cadmium and arsenic accumulation in rice grains. Plant Cell Physiol 58:1730–1742CrossRefGoogle Scholar
- Wysocka-Diller J, Helariutta Y, Fukaki H, Malamy J, Benfey P (2000) Molecular analysis of SCARECROW function reveals a radial patterning mechanism common to root and shoot. Development 127:595–603Google Scholar