Comparison of two ecotypes of the metal hyperaccumulator Thlaspi caerulescens (J. & C. PRESL) at the transcriptional level

Abstract

This paper investigates differences in gene expression among the two Thlaspi caerulescens ecotypes La Calamine (LC) and Lellingen (LE) that have been shown to differ in metal tolerance and metal uptake. LC originates from a metalliferous soil and tolerates higher metal concentrations than LE which originates from a non-metalliferous soil. The two ecotypes were treated with different levels of zinc in solution culture, and differences in gene expression were assessed through application of a cDNA microarray consisting of 1,700 root and 2,700 shoot cDNAs. Hybridisation of root and shoot cDNA from the two ecotypes revealed a total of 257 differentially expressed genes. The regulation of selected genes was verified by quantitative reverse transcriptase polymerase chain reaction. Comparison of the expression profiles of the two ecotypes suggests that LC has a higher capacity to cope with reactive oxygen species and to avoid the formation of peroxynitrite. Furthermore, increased transcripts for the genes encoding for water channel proteins could explain the higher Zn tolerance of LC compared to LE. The higher Zn tolerance of LC was reflected by a lower expression of the genes involved in disease and defence mechanisms. The results of this study provide a valuable set of data that may help to improve our understanding of the mechanisms employed by plants to tolerate toxic concentrations of metal in the soil.

Phytoextraction of zinc by the hyperaccumulator Noccaea caerulescens: accumulation, distribution and multi-element interactions

“…There was a change in the expression of the Cu/Zn superoxide dismutase gene at different concentrations of Zn supply. The gene was repressed when the medium had no Zn and it was induced when Zn exposure increased from 100 µM to 1000 µM (Plessl et al, 2010).…”

“…According to this study, 23.8-60.4% of the variance for the trait in N. caerulescens was explained by QTL. It is possible to gather the selected Znresponsive genes into functional groups such as oxidative stress, transport processes and energy supply (Plessl et al, 2010). There was a change in the expression of the Cu/Zn superoxide dismutase gene at different concentrations of Zn supply.…”

“…It typically has a biomass from 140 to 360 mg DW per plant (Knight et al, 1997) although its growth rate and biomass vary widely in its natural populations (Reeves et al, 2001;Plessl et al, 2010). Increasing the supply of Zn from 1 to 10 mmol m -3 in solution increased the total DW of this species by 19% .…”

“…A limitation of using N. caerulescens for Zn phytoextraction is its low biomass (Knight et al, 1997;Reeves et al, 2001) and the large variability in growth rate and biomass in natural populations (Reeves et al, 2001;Plessl et al, 2010). It was known to have higher biomass and lower mortality rates when grown on contaminated industrial soil than on agricultural soil (Saison et al, 2004).…”

“…It was reported that the whole process of metal accumulation by hyperaccumulators, including Zn uptake, divides into five stages: mobilization, uptake and sequestration, xylem transport, unloading and tissues distribution (Clemens et al, 2002;Lombi et al, 2002a;Yang et al, 2005). Modelling typical genetic characteristics of the plant and specific proteins involved in the Zn transport into the plant cells such as ZIP family, HMA (heavy-metal-ATPases) and MTP (metal tolerance protein) has been developed to simulate the mechanisms involving in tolerance and hyperaccumulation of Zn (Lasat et al, 1996;MacDiarmid et al, 2000;Pence et al, 2000;Clemens, 2001;Deniau et al, 2006;Plessl et al, 2010). The models can be used to identify constraints to efficient Zn phytoextraction for marketable phytoextration of N. caerulescens.…”