JAEA-Review-2010-065.pdf:15.99MB - 日本原子力研究開発機構

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Visualization of 107 Cd Accumulation
in Oilseed Rape Plants Treated with Glutathione
S. Nakamura a) , N. Suzui b) , S. Ito b) , N. Kawachi b) , N. S. Ishioka b) ,
H. Rai a) , H. Hattori a) , M. Chino a) and S. Fujimaki b)
a) Faculty of Bioresource Sciences, Akita Prefectural University,
b) Radiation-Applied Biology Division, QuBS, JAEA
Cadmium (Cd) is one of toxic heavy metals. Cd
accumulation in human bodies leads to serious health
problems. Cd accumulates in human bodies mainly
through consumption of agricultural products. It is
necessary to reduce Cd accumulation in agricultural
products in order to inhibit Cd accumulation in human
bodies. However, critical technologies to reduce Cd
accumulation in agricultural products have not yet been
realized. To realize these technologies, it is needed to
understand mechanisms of Cd long-distance transport and
Cd accumulation in higher plants. However, these
mechanisms are not well understood so far. Glutathione
(GSH) is a major low molecular weight thiol tripeptide,
consisting of cysteine, glutamic acid, and glycine. GSH is
involved in many aspects of metabolism in plants. In our
previous work, GSH concentration in the phloem sap
collected from oilseed rape plants increased by Cd
1)
treatment . These results suggested that GSH might be
playing important roles in controlling Cd long-distance
transport and accumulation in plants. In this work, we
investigated effects of GSH to Cd long-distance transport
and accumulation by using positron emitting tracer imaging
system (PETIS). PETIS is a planner imaging system. We
can obtain serial images of distribution of positron emitting
2)
molecules in the plant body non-invasively . We already
have succeeded in visualizing Cd absorption, transport and
3)
accumulation in rice plants by using PETIS .
107
Cd (half-life: 6.5 h) was used as positron-emitting
radioactive tracer in our PETIS experiments. 107 Cd was
produced by bombarding silver plate with an energetic
proton beam delivered from AVF cyclotron at TIARA
(Takasaki Ion Accelerators for Advanced Radiation
Application). Produced 107 Cd was purified, following the
4) 107
method of Ishioka et al . Purified Cd was used for
PETIS experiments. Oilseed rape plants (Brassica napus)
were grown hydroponically in a growth chamber where the
plant growth conditions were controlled completely for two
weeks after sowing. PETIS experiments were also
performed in the growth chamber under controlled growth
conditions. After setting two week old oilseed rape plants
in the chamber, PETIS experiments were started by adding
purified 107 Cd in the nutrient solutions which were including
GSH. In these experiments, 10 M Cd was added to
hydroponic solutions as a carrier. Time-series images of
the 107 Cd distribution were obtained every four minute for
36 h. After PETIS experiments, 107 Cd accumulation in the
plant body of oilseed rape plants were investigated
JAEA-Review 2010-065
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thoroughly by using an imaging instrument (BAS-1500;
Fujifilm, Tokyo, Japan).
We succeeded to obtain fine serial images of Cd transport
and accumulation in oilseed rape plants (data not shown).
We also succeeded to obtain images of 107 Cd accumulation
in these plants by using an imaging instrument (Fig. 1).
107 Cd signals were observed in the shoot and root of oilseed
rape plants. In the shoot, Cd accumulation was inhibited
by GSH treatment (Fig. 1A and 1B). However, we could
not see any difference in the Cd accumulation in the root of
oilseed rape plants (Fig. 1C and 1D). Further research
enables us to understand effects of GSH on Cd long-distance
transport and accumulation in oilseed rape plants.
References
1) S. Nakamura et al., Sulfur Transport and Assimilation in
Plants in the Post Genomic Era (2005) 229-232.
2) S. Fujimaki, ITE Let. (2007) 8, C1-C10.
3) S. Fujimaki et al., Plant Physiol. 152 (2010) 1796-1806.
4) N. S. Ishioka et al., JAEA Takasaki Ann. Rep. 2005
(2006) 162.
A. B.
C. D.
Fig. 1 107 Cd accumulation in the plant body of oilseed
rape plants. These images were obtained by using
an imaging instrument (BAS-1500). A; Shoot of
oilseed rape plant (Control), B; Shoot of oilseed rape
plant (GSH treated), C; Root of oilseed rape plant
(Control), D; Root of oilseed rape plant (GSH
treated).