FIGURE LEGENDS
FIGURE 1 Symptoms of biuret toxicity in rice plants. Rice
seedlings were hydroponically grown in a culture solution supplemented
with 0, 0.1, 0.3, and 1.0 mmol L-1 biuret. (a) Plant
heights of 7-day-old seedlings. The data represent means ± SD (n =
22-24). Different alphabets indicate significant differences between
groups (p < 0.05, Tukey test). (b) Representative
images of 7-day-old seedlings.
FIGURE 2 Relative expression levels of biuret hydrolasein transgenic rice plants.
The expression in the youngest leaf at the vegetative growth stage was
determined via real-time PCR. Ubiquitin and Actin1 were
used as internal standards for normalization. The values are means of
two technical replicates. In names of transgenic lines, the combination
of the first and second numbers indicates a callus derived from a single
seed, and the third number indicates an individual plant regenerated
from the callus.
FIGURE 3 Biuret-decomposing activities of crude extracts of
rice plants.
Crude extracts were prepared from shoots of individual 19-day-old
wild-type Nipponbare (solid boxes, n = 3) and transgenic B3-9-1 (solid
circles, n =2) plants and 16-day-old B2-3-3-3 (open circles, n = 2).
Extracts were incubated at 30ºC with 50 mmol L-1sodium phosphate buffer (pH 8) and 3 mmol L-1 biuret.
The reaction was stopped by adding 0.5 mol L-1H2SO4. The amount of ammonia released
from biuret was determined using indophenol blue. The data represent
means ± SD.
FIGURE 4 Biuret tolerance of a transgenic rice line
overexpressing exogenous biuret hydrolase . Biuret treatment (0
and 0.3 mmol L-1) was started two days after the
sowing process. Photos were taken 9 days after sowing. Wild-type rice
plants (left panel) and transgenic rice plants (line B2-3-3-3, right
panel) grown without and with biuret.
Table 1 15N-Biuret uptake in rice plants.
Nineteen-day-old Nipponbare seedlings were exposed to 0.3 mmol
L-1 15N-biuret for 48 hr. Two plants
were maintained in a 40-mL vial. Values are expressed as means ± SD (n =
3).
Dry weight Total-N Biuret-derived N
(mg vial-1) (mmol g-1 DW) (µmol
g-1 DW) (µmol vial-1)
Shoots 124 ± 3.88 2.43 ± 0.09 13.5 ± 1.02 1.67 ± 0.18
Roots 23.8 ± 1.06 1.75 ± 0.01 5.83 ± 0.55 0.13 ± 0.01