Evolution of copper-tolerance and increased expression of a 2b-type metallothionein gene in Silene paradoxa L. populations

• Published in: Plant and soil 2003-12, Vol.257 (2), p.451-457
• Main Authors: Mengoni, A, Gonnelli, C, Hakvoort, H.W.J, Galardi, F, Bazzicalupo, M, Gabbrielli, R, Schat, H
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Applied ecology; Arid zones; Autoecology; Biological and medical sciences; Colle; Complementary DNA; Copper; DNA; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on plants and fungi; Evolution; Fundamental and applied biological sciences. Psychology; Gene expression; gene overexpression; Genes; Genetics of eukaryotes. Biological and molecular evolution; Hooves; leaves; loci; messenger RNA; metal tolerance; metallothionein; mine spoil; molecular sequence data; mt2b gene; mt2b locus; nucleotide sequences; Plant cytology, morphology, systematics, chorology and evolution; Plant evolution; Plants; Plants and fungi; polluted soils; Population genetics, reproduction patterns; Population growth; Pteridophyta, spermatophyta; Reverse transcriptase polymerase chain reaction; Salinity; serpentine soils; Silene; structural genes; Vegetals
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1023/a:1027325907996

Two independently evolved cupricolous populations, their ancestral serpentine population, another unrelated serpentine population and a non-metallicolous population of Silene paradoxa L. were compared for copper tolerance and foliar transcript levels of a 2b-type metallothionein gene that was previously shown to be involved in copper tolerance in the congener, S. vulgaris. The levels of copper tolerance and constitutive MT2b expression, assessed by Northern-blot analysis and semiquantitative RT-PCR, were proportionally increased in the cupricolous populations, as compared to the serpentine and the non-metallicolous populations. Southern-blot analysis revealed amplification of the gene in the cupricolous populations, such as in S. vulgaris, which might account for the higher constitutive expression level. Since the cupricolous populations descended separately from a common serpentine ancestral population, these results imply that MT2b overexpression must have been independently evolved in both of them, again such as previously shown S. vulgaris. Thus, both in S. paradoxa and S. vulgaris, the MT2b locus appears to be a major target for natural selection imposed by soil copper toxicity.