ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
P140. Metallothioneins – What Are Their Physiological Functions in
Barley?
J. Nymark Hegelund , M. Schiller , S. Husted , J.K. Schjoerring
Agricultural Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Denmark
e-mail: jnh@life.ku.dk
Metallothioneins (MTs) are a family of small cysteine rich metalloproteins (Mr < 10 kDa). In vivo MTs have
been found to coordinate Zn, Cu and Cd. Metallothioneins in mammals have been associated with numerous
physiological functions such as heavy metal detoxification, scavenging of reactive oxygen species[1], and metal
loading of transcription factors[2]. Transcripts of plant MTs are induced by metal ions, hormones, wounding and
oxidative stress[3, 4, 5]. However at the protein level, plant MTs are not well characterized.
The entire MT family of barley have been cloned to characterize their physiological functions and redundancies.
We are particularly focusing on the importance of MTs during ear development in monocots. During grain
development, Zn, Cu and possibly Cd are mobilized from roots and leaves and stored in the aleurone, embryo
and endosperm tissues of the grain. Using the stabile Zn67 isotope as a tool, we have managed to relate Zn
remobilization to the developing ear to the expression of barley MTs. Transcripts of 6 barley MTs are abundant
in developing grains. However, the protein levels arising from the MT transcripts are uncertain. We chemically
analyze the composition of Zn, Cu and Cd binding compounds in barley seeds using HPLC-ICP-MS and LC-
ESI-QTOF-MS. These methods detect barley MTs expressed in and purified from E. coli. Ultimately, the
identification of barley MTs in vivo will provide valuable new knowledge to the physiological functions of plant
MTs.
References:
[1] Coyle P. et.al. (2002) Cell. Mol. Life Sci. 59 (2002) 627-647
Metallothionein: The multipurpose protein
[2] Huang M. et.al. (2004) J. Inorg. Biochem. 98 639-648
Interprotein metal exchange between transcription factor IIIa and apo-metallothionein
[3] Lü S. et.al. (2007) Transgenic Res 16:177-191
The GUS reporter-aided analysis of the promoter activities of a rice metallothionein gene reveals different
regulatory regions responsible for tissue-specific and inducible expression in transgenic Arabidopsis
[4] Yuan J. et.al. (2008) Plant Physiol, April 2008, Vol. 146, pp. 1637-1650,
Characteristic and Expression Analysis of a Metallothionein Gene, OsMT2b, Down-Regulated by Cytokinin
Suggests Functions in Root Development and Seed Embryo Germination of Rice
[5] Obertello M. et. al. (2007) MPMI Vol. 20: 10, 1231-1240.
Functional Analysis of the Metallothionein Gene cgMT1 Isolated from the Actinorhizal Tree Casuarina glauca
_____________________________________________________________________
259