Chloroplast targeting of phytochelatin synthase in Arabidopsis:: effects on heavy metal tolerance and accumulation

被引:42
作者
Picault, N.
Cazale, A. C.
Beyly, A.
Cuine, S.
Carrier, P.
Luu, D. T.
Forestier, C.
Peltier, G.
机构
[1] CEN Cadarache, DSV, DEVM, Lab Ecophysiol Photosynthese,UMR 6191,CNRS, F-13108 St Paul Les Durance, France
[2] CEA Cadarache, DSV, DEVM,CNRS, Lab Echanges Membranaires & Signalisat,UMR 6191, F-13108 St Paul Les Durance, France
关键词
phytochelatin synthase; chloroplast; cytosol; cadmium; arsenic;
D O I
10.1016/j.biochi.2006.04.016
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The enzymatically synthesized thiol peptide phytochelatin (PC) plays a central role in heavy metal tolerance and detoxification in plants. In response to heavy metal exposure, the constitutively expressed phytochelatin synthase enzyme (PCS) is activated leading to synthesis of PCs in the cytosol. Recent attempts to increase plant metal accumulation and tolerance reported that PCS over-expression in transgenic plants paradoxically induced cadmium hypersensitivity. In the present paper, we investigate the possibility of synthesizing PCs in plastids by over-expressing a plastid targeted phytochelatin synthase (PCS). Plastids represent a relatively important cellular volume and offer the advantage of containing glutathione, the precursor of PC synthesis. Using a constitutive CaMV 35S promoter and a RbcS transit peptide, we successfully addressed AtPCS1 to chloroplasts, significant PCS activity being measured in this compartment in two independent transgenic lines. A substantial increase in the PC content and a decrease in the glutathione pool were observed in response to cadmium exposure, when compared to wild-type plants. While over-expressing AtPCS1 in the cytosol importantly decreased cadmium tolerance, both cadmium tolerance and accumulation of plants expressing plastidial AtPCS1 were not significantly affected compared to wild-type. Interestingly, targeting AtPCS1 to chloroplasts induced a marked sensitivity to arsenic while plants over-expressing AtPCS1 in the cytoplasm were more tolerant to this metalloid. These results are discussed in relation to heavy metal trafficking pathways in higher plants and to the interest of using plastid expression of PCS for biotechnological applications. (c) 2006 Elsevier Masson SAS. All rights reserved.
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页码:1743 / 1750
页数:8
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