Abstract
Brassica juncea L. is a Zn/Cd accumulator. To determine the physiological basis of its metal accumulation phenotype, the functional properties and role of the metal efflux transporter BjCET2 were investigated using transgenic technology. Heterologous expression of BjCET2 in the double mutant yeast strain Δzrc1Δcot1 enhanced the metal tolerance of the yeast strain and led to decrease in Zn or Cd accumulation. Detection of green fluorescence from green fluorescent protein (GFP) in the root tip of transgenic tobacco further revealed that BjCET2::GFP is localized at the plasma membrane. Semi-quantitative RT-PCR analysis showed that BjCET2 was most abundant in the root and was weakly expressed in the stem and leaves. The expression of BjCET2 was up-regulated by heavy metals. However, exposure to low temperature, salt and drought did not affect the expression of BjCET2. Overexpression of BjCET2 in transgenic B. juncea plants conferred heavy metal tolerance and increased Cd/Zn accumulation in the leaves. BjCET2-deficient B. juncea mediated by antisense RNA resulted in hypersensitivity to heavy metals and decreased Zn/Cd accumulation in the plants. These results suggest that the heavy metal efflux of BjCET2 plays important roles in the metal tolerance of B. juncea and in Zn/Cd accumulation in B. juncea.
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References
Clemens S, Palmgren MG, Kramer U (2002) A long way ahead: understanding and engineering plant metal accumulation. Trends Plant Sci 7:309–314
Desbrosses-Fonrouge A, Voigt K, Schröder A, Arrivault S, Thomine S, Krämer U (2005) Arabidopsis thaliana MTP1 is a Zn transporter in the vacuolar membrane which mediates Zn detoxification and drives leaf Zn accumulation. FEBS Lett 579:4165–4174
Ebbs SD, Kochian LV (1997) Toxicity of zinc and copper to Brassica species: implications for phytoremediation. J Environ Qual 26:776–778
Gaither LA, Eide DJ (2000) Functional expression of the human hZIP2 zinc transporter. J Biol Chem 275:5560–5564
Gorinova N, Nedkovska M, Todorovska E, Simova-Stoilova L, Stoyanova Z, Georgieva K, Demirevska-Kepova K, Atanassov A, Herzig R (2007) Improved phytoaccumulation of cadmium by genetically modified tobacco plants (Nicotiana tabacum L.). Physiological and biochemical response of the transformants to cadmium toxicity. Environ Pollut 16:1–170
Hernandez LE, Carpena-Ruiz R, Garate A (1996) Alterations in the mineral nutrition of pea seedlings exposed to cadmium. J Plant Nutr 19:1581–1598
Ito H, Fukuda Y, Murata K, Kimura A (1983) Transformation of intact yeast cells treated with alkali cations. J Bacteriol 153:163–168
Kim D, Gustin JL, Lahner B, Persans MW, Baek D, Yun DJ, Salt DE (2004) The plant CDF family member TgMTP1 from the Ni/Zn hyperaccumulator Thlaspi goesingense acts to enhance efflux of Zn at the plasma membrane when expressed in Saccharomyces cerevisiae. Plant J 39:237–251
Kobae Y, Uemura T, Sato MH, Ohnishi M, Mimura T, Nakagawa T, Maeshima M (2004) Zinc transporter of Arabidopsis thaliana AtMTPl is localized to vacuolar membranes and implicated in zinc homeostasis. Plant Cell Physiol 45:1749–1758
Krämer U, Talkea IN, Hanikenne M (2007) Transition metal transport. FEBS Lett 581:2263–2272
Lang ML, Zhang YX, Guan ZQ, Chai TY (2005) PCR-enriched cDNA pool method for cloning of gene homologues. Plant Mol Biol Rep 23:219–226
Macek T, Mackova M, Pavlikova D, Szakova J, Truksa M, Singh Cundy A, Kotrba P, Yancey N, Scouten WH (2002) Accumulation of cadmium by transgenic tobacco. Acta Biotechnologica 22:101–106
McGrath SP, Zhao FJ, Lombi E (2002) Phytoremediation of metals, metalloids and radionuclides. Adv Agron 75:156
Miyabe S, Izawa S, Inoue Y (2001) The Zrc1 is involved in zinc transport system between vacuole and cytosol in Saccharomyces cerevisiae. Biochem Biophys Res Commun 282:79–83
Murashige T, Skoog F (1962) A revised medium for rapid growth and bio assays with tobacco tissue cultures. Physiol Plant 15:473–497
Muthukumar B, Yakubov B, Salt DE (2007) Transcriptional activation and localization of expression of Brassica juncea putative metal transport protein BjMTP1. BMC plant biol. doi:10.1186/1471-2229-7-32
Rigola D, Fiers M, Vurro E, Aarts MGM (2006) The heavy metal hyperaccumulator Thlaspi caerulescens expresses many species-specific genes, as identified by comparative expressed sequence tag analysis. New Phytol 170:753–766
Woolhouse HW (1983) Encyclopedia of plant physiology: responses to the chemical and biological environment, vol. sNew Series vol 12 C, Springer, Berlin
Xu J, Zhang YX, Wei W, Han L, Guan ZQ, Wang Z, Chai TY (2008) BjDHNs confer heavy-metal tolerance in plants. Mol Biotechnol. doi:10.1007/s12033-007-9005-8
Zhang YX, Xu J, Han L, Wei W, Guan ZQ, Cong L, Chai TY (2006) Highly efficient shoot regeneration and Agrobacterium-mediated transformation protocol of Brassica juncea. Plant Mol Biol Rep 24:255a–255i
Acknowledgments
The research was supported by the National High Technology Planning Program of China (Grant nos. 2006AA10Z407), the National Major Special Project on New Varieties Cultivation for Transgenic Organisms (Grant nos. 2009ZX08009-130B), and China National Natural Sciences Foundation (Grant no. 30570146).
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Communicated by K. Chong.
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Xu, J., Chai, T., Zhang, Y. et al. The cation-efflux transporter BjCET2 mediates zinc and cadmium accumulation in Brassica juncea L. leaves. Plant Cell Rep 28, 1235–1242 (2009). https://doi.org/10.1007/s00299-009-0723-1
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DOI: https://doi.org/10.1007/s00299-009-0723-1