Yeast metallothionein in transgenic tobacco promotes copper uptake from contaminated soils.
Metallothioneins (MTs) are metal-binding proteins that confer heavy metal tolerance and accumulation in yeast. To augment higher plant metal sequestration, the yeast metallothionein (CUP 1) was introduced into tobacco plants. The CUP 1 gene expression and copper and cadmium phytoextraction were determined. To confirm transformation, selfed and kanamycin-resistant third generation plants were subjected to DNA blot and polymerase chain reaction (PCR) analysis. A 4 mM CuSO(4) stress for 7 days resulted in a decline in CUP 1 transcripts versus nonstress conditions. Despite low mRNA levels, CUP 1 transformants accumulated up to seven times more copper in older versus younger leaves during copper stress. Pooled leaves of transgenic plants grown in soils from copper stamp-sands contained two to three times the copper content as that of the control plants. Unlike some previous reports featuring MT overexpression in plants, CUP 1 seedlings did not significantly sequester or demonstrate tolerance to CdCl(2). Using this transgenic approach, yeast CUP 1 expression under nonstressed conditions contributed to copper metal phytoextraction during a subsequent copper challenge. This strategy could be incorporated into plants designed for enhanced phytoremediation of metal contaminants.
Thomas
John C
JC
Biological, Environmental, and Geology Sciences, Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Rd., Dearborn, Michigan 48128-1491, USA. jcthomas@umd.umich.edu
Davies
Elizabeth C
EC
Malick
Farah K
FK
Endreszl
Charles
C
Williams
Chandra R
CR
Abbas
Mohammed
M
Petrella
Sally
S
Swisher
Krystal
K
Perron
Mike
M
Edwards
Ryan
R
Osenkowski
Pam
P
Urbanczyk
Nicolas
N
Wiesend
Wendy N
WN
Murray
Kent S
KS
Ostenkowski
Pam
P
D000595:Amino Acid Sequence; D001673:Biodegradation, Environmental; D003300:Copper / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D007220:Industrial Waste / Q000517:prevention & control; D008668:Metallothionein / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000378:metabolism*; D015202:Protein Engineering / Q000379:methods*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012037:Refuse Disposal / Q000379:methods; D012989:Soil Pollutants / Q000378:metabolism*; D014026:Nicotiana / Q000235:genetics* / Q000378:metabolism*
D005656:Fungal Proteins; D007220:Industrial Waste; D011994:Recombinant Proteins; D012989:Soil Pollutants; C007121:copper thionein; D003300:Copper; D008668:Metallothionein