Gene Expression Differences between Noccaea caerulescens Ecotypes Help to Identify Candidate Genes for Metal Phytoremediation
Halimaa, P. ; Lin, Y.F. ; Ahonen, V.H. ; Blande, D. ; Clemens, S. ; Gyenesei, A. ; Haikio, E. ; Karenlampi, S.O. ; Laiho, A. ; Aarts, M.G.M. ; Pursiheimo, J.P. ; Schat, H. ; Schmidt, H. ; Tuomainen, M.H. ; Tervahauta, A.I. - \ 2014
Environmental Science and Technology 48 (2014)6. - ISSN 0013-936X - p. 3344 - 3353.
hyperaccumulator thlaspi-caerulescens - arabidopsis-halleri - commercial phytoextraction - cadmium tolerance - cd tolerance - copy number - key role - accumulation - transporter - plants
Populations of Noccaea caerulescens show tremendous differences in their capacity to hyperaccumulate and hypertolerate metals. To explore the differences that could contribute to these traits, we undertook SOLiD high-throughput sequencing of the root transcriptomes of three phenotypically well-characterized N. caerulescens accessions, i.e., Ganges, La Calamine, and Monte Prinzera. Genes with possible contribution to zinc, cadmium, and nickel hyperaccumulation and hypertolerance were predicted. The most significant differences between the accessions were related to metal ion (di-, trivalent inorganic cation) transmembrane transporter activity, iron and calcium ion binding, (inorganic) anion transmembrane transporter activity, and antioxidant activity. Analysis of correlation between the expression profile of each gene and the metal-related characteristics of the accessions disclosed both previously characterized (HMA4, HMA3) and new candidate genes (e.g., for nickel IRT1, ZIP10, and PDF2.3) as possible contributors to the hyperaccumulation/tolerance phenotype. A number of unknown Noccaea-specific transcripts also showed correlation with Zn2+, Cd2+, or Ni2+ hyperaccumulation/tolerance. This study shows that N. caerulescens populations have evolved great diversity in the expression of metal-related genes, facilitating adaptation to various metalliferous soils. The information will be helpful in the development of improved plants for metal phytoremediation.
Isolation of Zn-responsive genes from two accessions of the hyperaccumulator plant Thlaspi caerulescens
Hassinen, V.H. ; Tervahauta, A.I. ; Halimaa, P. ; Plessl, M. ; Peraniemi, S. ; Schat, H. ; Aarts, M.G.M. ; Servomaa, K. ; Karenlampi, S.O. - \ 2007
Planta 225 (2007)4. - ISSN 0032-0935 - p. 977 - 989.
zinc-transporter genes - heavy-metal tolerance - arabidopsis-thaliana - differential display - abc-transporter - accumulation - expression - metallothionein - identification - homeostasis
Several populations with different metal tolerance, uptake and root-to-shoot transport are known for the metal hyperaccumulator plant Thlaspi caerulescens. In this study, genes differentially expressed under various Zn exposures were identified from the shoots of two T. caerulescens accessions (calaminous and non-calaminous) using fluorescent differential display RT-PCR. cDNA fragments from 16 Zn-responsive genes, including those encoding metallothionein (MT) type 2 and type 3, MRP-like transporter, pectin methylesterase (PME) and Ole e 1-like gene as well as several unknown genes, were eventually isolated. The full-length MT2 and MT3 sequences differ from those previously isolated from other Thlaspi accessions, possibly representing new alleles or isoforms. Besides the differential expression in Zn exposures, the gene expression was dependent on the accession. Thlaspi homologues of ClpP protease and MRP transporter were induced at high Zn concentrations. MT2 and PME were expressed at higher levels in the calaminous accession. The MTs and MRP transporter expressed in transgenic yeasts were capable of conferring Cu and Cd tolerance, whereas the Ole e 1-like gene enhanced toxicity to these metals. The MTs increased yeast intracellular Cd content. As no significant differences were found between Arabidopsis and Thlaspi MTs, they apparently do not differ in their capacity to bind metals. However, the higher levels of MT2 in the calaminous accession may contribute to the Zn-adapted phenotype.