© 2007 Heron Publishing—Victoria, Canada
Isolation of genes up-regulated by copper in a copper-tolerant birch (Betula pendula) clone
Sirpa I. Keinänen (1), Viivi H. Hassinen (1), Sirpa O. Kärenlampi (1) and Arja I. Tervahauta (1, 2)
1. University of Kuopio, Institute of Applied Biotechnology, P.O. Box 1627, FIN-70211 Kuopio, Finland / 2. Corresponding author (arja.tervahauta@uku.fi) / Received June 15, 2006; accepted October 19, 2006; published online June 1, 2007
Summary
Suppression subtractive hybridization (SSH) was used to isolate genes differentially expressed following exposure to copper
(Cu) in a naturally selected Cu-tolerant birch (Betula pendula Roth.) clone originating from a disused lead/zinc smelter. Of the 352 cDNA fragments initially isolated, 108 were up-regulated
by Cu, of which 55 showed over twofold induction by macroarray analysis. Searches against protein databases (Blastx) and sequence
analysis provided the tentative identity of 21 genes. Three fragments lacked homology to any sequences in the databases. Most
of the identified genes are involved in cellular transport, regulation or cell rescue and defense. Several genes have not
previously been reported to be up-regulated by Cu, e.g., plasma intrinsic protein 2, glutamine synthetase and multi-drug resistance-associated
protein (MRP4). The expression of MRP4, a vacuolar sorting receptor-like protein and an unidentified gene was studied in more detail by quantitative real-time PCR.
These genes showed stronger up-regulation by Cu in the roots and shoots of the Cu-tolerant birch clone compared with a less
tolerant clone. Clear clonal differences in gene expression were observed, e.g., for the regulator of chromosome condensation
family protein, DnaJ protein homolog, vacuolar sorting receptor-like protein and MRP4. These findings contribute to our understanding of Cu tolerance in birch, a pioneer plant in metal-contaminated soils.
Keywords:
metal tolerance, suppression subtractive hybridization.
