Heavy Metals and Phytoremediation
Punyasuk, Napassorn , Meetam, Metha , Goldsbrough, Peter .
Functional Analysis of Seed-Expressed Metallothioneins in Arabidopsis.
Metallothioneins (MTs) comprise a family of small cysteine-rich proteins found in most eukaryotes and some bacteria. In angiosperms, type 4 MTs are expressed predominantly in seeds. To understand the functions of MTs in seeds, we are studying the MT gene family in Arabidopsis thaliana. Arabidopsis seeds contain abundant levels of RNAs for MT4a, MT4b, and MT2a. MT4a and MT4b are only expressed in seeds whereas MT2a is also expressed in vegetative tissues. MT4a and MT4b RNAs accumulate during late embryogenesis and disappear rapidly upon imbibition. GUS expression directed by the MT2a promoter was restricted to cotyledons of the embryo whereas the MT4a and MT4b promoters were active in all embryonic tissues. Arabidopsis mutants that lacked these MTs were normal in terms of seed development and germination. However, seeds of the mt2a-1, mt4a-1 and mt4b-1 mutants contained reduced amounts of copper. A small but significant reduction in zinc content was also observed in seeds from the mt4a-1 mutant and the mt4a-1/mt4b-1 double mutants. When expressed in metal-sensitive yeast mutants, MT4a and MT4b were equally able to provide copper tolerance, but MT4a was more efficient than MT4b in conferring zinc tolerance. These results suggest that MTs have specific roles in accumulation of copper and zinc during seed development. To confirm the differences in metal binding properties of these type 4 MTs, MT4a and MT4b were ectopically expressed in Arabidopsis under 35S promoter. Phenotypic analysis of these transgenic plants and the metal binding properties of Arabidopsis MTs expressed in bacteria will be presented.
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1 - Purdue University, Horticulture and Landscape Architecture, 625 Agriculture Mall Dr., West Lafayette, IN, 47907-2010, USA
2 - Purdue University, Botany and Plant Pathology
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM