Isolation of Zn-responsive genes from two accessions of the hyperaccumulator plant Thlaspi caerulescens

Abstract

Several populations with diVerent metal tolerance, uptake and root-to-shoot transport are known for the metal hyperaccumulator plant Thlaspi caerulescens. In this study, genes diVerentially expressed under various Zn exposures were identiWed from the shoots of two T. caerulescens accessions (calaminous and non-calaminous) using Xuorescent diVerential 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 fulllength MT2 and MT3 sequences diVer from those previously isolated from other Thlaspi accessions, possibly representing new alleles or isoforms. Besides the diVerential 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 signiWcant diVerences were found between Arabidopsis and Thlaspi MTs, they apparently do not diVer in their capacity to bind metals. However, the higher levels of MT2 in the calaminous accession may contribute to the Zn-adapted phenotype.

Characteristic and Expression Analysis of a Metallothionein Gene, OsMT2b, Down-Regulated by Cytokinin Suggests Functions in Root Development and Seed Embryo Germination of Rice

“…For plant, MTs can efficiently bind metals (Murphy et al, 1997;Leszczyszyn et al, 2007) and some of them are transcriptionally regulated by metals; they are also thought to play important roles in metal tolerance, detoxification, and homeostasis in plants (Cobbett and Goldsbrough, 2002;Hall, 2002;Hassinen et al, 2007). On the other hand, there were also intensive studies for the responses of MTs to stress conditions, such as draft and reactive oxidant species (Akashi et al, 2004;Wong et al, 2004).…”

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

“…Recently, Zn-responsive genes from two accessions of T. caerulescens have been reported (Hassinen et al 2007), and an expressed sequence tag (EST) collection from T. caerulescens zinc-exposed roots and shoots has been published (Rigola et al 2006). Here, we report on the development of a microarray spotted with the T. caerulescens cDNAs out of this collection and present the results of the comparative transcript profiling of the roots and shoots from two different T. caerulescens ecotypes grown at different Zn exposures.…”

Cloning and characterization of a type 1 metallothionein gene from the copper-tolerant plant Elsholtzia haichowensis

“…In some plant species, Cu tolerance is associated with constitutively enhanced transcript levels of a type 2 MT (Murphy and Taiz 1995;van Hoof et al 2001;Mengoni et al 2003). Gene expression analyses and functional testing in yeast have revealed a role for MTs in Cu homeostasis and detoxification (Zhou and Goldsbrough 1994;Ma et al 2003;Roosens et al 2004;Hassinen et al 2007). In addition, plant MTs are involved in important physiological processes, including fruit ripening (Moyle et al 2005), root development, embryo germination , and suberization (Mir et al 2004).…”