Botanical Studies (2007) 48: 35-41.
*
Corresponding author: E-mail: zhangmy2005@yahoo.com.
cn; Tel/Fax: 0086-20-37252891.
INTRODUCTION
Like the synthesis and cycling of glutathione (GSH),
GSH transport systems also have important roles
in sustaining the normal development of plants and
protecting them from biotic and abiotic stresses (Foyer
et al., 2001). GSH is not produced at equivalent rates by
all tissues, or even by all cells within a tissue (May et al.,
1998; Noctor et al., 2002). The trichomes on the stem
and leaf surface of Arabidopsis, for example, show much
higher expression of enzymes involved in the synthesis
of cysteine and GSH; and have GSH contents 2-3 times
higher than the surrounding basal and epidermal cells
(Gutierrez-Alcala et al., 2000).
The GSSG (oxidized glutathione) and GS-conjugated
transport systems on the plasma membrane associated with
systemic transport have been previously reviewed (Foyer
et al., 2001). The differential intercellular partitioning of
the GSH metabolism has been observed in maize (Doulis
et al., 1997), and in broad bean leaf tissues (Jamai et al.,
1996). GSH is also a major means of transporting reduced
sulfur over long distances, within both the xylem and the
phloem (Rennenberg et al., 1979; Herschbach et al., 2000).
Long distance GSH transport has also been implicated
in different roles, including phloem-mediated shoot-to-
root allocation of and demand-driven control of sulfate
uptake and/or loading into the xylem stream by the roots
in herbaceous plants (Lappartient and Touraine, 1997).
Recently, two plant GSH transporters, BjGT1 from
Brassica juncea (Bogs et al., 2003) and OsGT1 from
Oryza sativa (Zhang et al., 2004), were shown to be able
to promote transport of GSH, GSSG, and glutathione
conjugates when they were used to complement yeast
mutants with defects in GSH transport. However, the
physiological functions and expression patterns of the rice
glutathione transporter (OsGT1) (Zhang et al., 2004) were
not studied. Here, Arabidopsis transgenic for the reporter
gene GUS under the control of the OsGT1 promoter
was used to analyze the expression patterns of OsGT1
at various developmental stages and after treatment with
NaCl, heavy metals, abscisic acid (ABA), naphthalene
acetic acid (NAA), salicylic acid (SA), gibberellin (GA),
and low temperature.
MATERIALS AND METHODS
Construction of different deletion OsGT1
promoter-GUS fusion
The promoter region of OsGT1 was identified from
the database of rice genome sequences: accession no.
AP001168. The 2246 bp putative OsGT1 promoter was
amplified from genomic DNA of Oryza sativa cv., nip-
ponbar and confirmed by sequencing. The sequence data
from this article have been deposited at NCBI under ac-
cession number AY338469. To generate promoter deletion
fragments of the putative OsGT1 promoter, sets of primers
were used to amplify different-length fragments of the pro-
moter. The 2230-bp fragment P
13
was from -2246 to -17 bp
Tissue and inducible expression of a rice glutathione
transporter gene promoter in transgenic Arabidopsis
Ya-Qin WANG
1
, Shu-Ying ZHU
2
, Ying WANG
2
, and Ming-Yong ZHANG
2,
*
1
School of Bioscience and Bioengineering, South China University of Technology, Guangzhou 510641, P.R. China
2
South China Botanical Garden, the Chinese Academy of Sciences, Xinkelu 723, Guangzhou 510650, P.R. China
(Received January 17, 2006; Accepted July 7, 2006)
ABSTRACT.
The promoter of a rice glutathione transporter (OsGT1) was fused to the reporter gene s-gluc-
uronidase (GUS) and introduced into Arabidopsis to analyze promoter and expression patterns. Deletion of
various length-promoter studies indicated that a 1246 bp fragment upstream of start codon (ATG) of OsGT1
is sufficient to activate the expression of GUS gene. The GUS assays revealed that the OsGT1 promoter is
expressed in an organ and tissue-specific manner. GUS was being expressed in the root stele, the veins of
cotyledons, the anthers and flower petals, but not in leaves or stems under normal growth conditions. GUS ex-
pression activated by the OsGT1 promoter was strongly stimulated by NaCl and low temperature, moderately
by abscisic acid and naphthaleneacetic acid, and not at all by salicylic acid and gibberellic acid. Expression
was inhibited by cadmium but not by copper. The function of OsGT1 in glutathione transport in normal or
stress conditions is discussed.
Keywords: Arabidopsis; Flower; Glutathione transporter; Promoter; Rice; Root.
MOLECULAR BIOLOGY