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575
27
576
Statements and Declarations
577
Funding: This work was supported in part by JSPS KAKENHI Grant Number JP19K05755.
578
579
Competing interests: The authors have no relevant financial or non-financial interests to
580
disclose.
581
582
Author contributions: Kumiko Ochiai and Toru Matoh conceived and designed the research.
583
Kumiko Ochiai and Yosuke Nomura performed experiments and analyzed the data. Asuka
584
Uesugi generated biuret hydrolase-overexpressing rice lines. Kumiko Ochiai wrote the
585
manuscript with input from other authors.
586
587
Data availability: the data supporting the findings of this study are available within the article
588
and its supplementary materials.
589
590
28
591
Figure legend
592
Fig. 1 Effects of biuret on dry weight (a, d), biuret concentration (b, e), and allantoin concentration
593
(c, f) in roots and shoots of 7-day-old wild-type rice plants (a–c) and 9-day-old biuret hydrolase-
594
overexpressing rice lines (d–f). Bars and circles represent mean and each sample, respectively.
595
nd means not detected. (a–c) Wild-type plants were grown with 0, 0,1, and 0.3 mmol L-1 biuret
596
supplemented in the culture solution. Ten seedlings were combined for a single sample. Different
597
alphabets indicate significant difference among treatments in each organ (p < 0.05, Tukey’s test,
598
n = 3). (d–f) Wild-type and two independent transgenic lines (B3-9-1 and B2-3-3) were grown
599
with or without 0.3 mmol L-1 biuret in the culture solution. Four to six plants were combined into
600
one sample. Gray and black bars represent control and biuret-treated plants, respectively.
601
Asterisks indicate significant difference between the treatment (*p < 0.05; **p < 0.01, Welch’s t-
602
test, n = 3). Different alphabets indicate significant difference in each organ (p < 0.05, Tukey’s
603
test, n = 3).
604
605
Fig. 2 Inhibitory effect of biuret for allantoinase activity. Crude extracts were prepared from
606
shoots of 9-day-old rice seedlings hydroponically grown without biuret. Extracts were incubated
607
at 30ºC with 10 mmol L-1 allantoin, 50 mmol L-1 Tricine-NaOH (pH8.0), 2mmol L-1 MnSO4, and
608
the desired concentration of biuret for 30min. The amount of allantoic acid produced from
609
allantoin was colorimetorically determined. Same shape symbols indicate a same crude extract.
610
Crossbars represent the mean value. The means were not significantly different among treatments
611
at 5% level (One-way ANOVA with blocking, n = 4).
612
613
Fig. 3 Relative expression of genes related to purine degradation and ureide metabolisms in roots
614
and shoots of 4 to 7-day old rice seedlings. Rice plants were hydroponically grown under the
615
control condition and 0.3 mmol L-1 biuret toxicity. Data obtained from two independent trials,
29
616
each with three replicates, are combined and shown. The relative expression levels of OsXO (a),
617
OsUO (b), OsALNS (c), OsALN (d), OsAAH (e), OsUGlyAH (f), OsUAH (g), OsUPS1 (h),
618
OsUPS2 (i), and OsUPS3 (j). The expression levels were normalized to the expression of
619
Ubiquitin and Actin1 and expressed in log2 scale. Gray and black symbols indicate control and
620
biuret treated samples, respectively. Crossbars indicate means of the six samples. Asterisks
621
indicate statistically significant difference between the treatments at the time point. *p < 0.05;
622
**p < 0.01; ***p < 0.001 (n = 6, Welch’s t-test). Numerical values above asterisks indicate log2
623
fold-change relative to the control plants.
624
625
Fig. 4 Principal component analysis of metabolomics profile of control and biuret-treated rice
626
suspension cells. Rice cells were transferred into a medium without biuret or with 0.3 mmol L-1
627
biuret and harvested 3 and 5 days after transfer. Closed symbols indicate control cells, and open
628
symbols indicate biuret-treated cells. Circles indicate day 3 samples, and triangles indicate day 5
629
samples.
630
631
Fig. 5 Normalized peak intensities of differentially accumulated metabolites between control and
632
biuret treated rice suspension cells. Peaks with significantly different intensity between the
633
control-group and biuret-group are shown in the list (p < 0.05, Welch’s t-test, n = 4). RT column
634
indicate retention time in second. In the formula column, the formula is shown when the formula
635
is uniquely determined from the m/z value, blank when there are multiple possible candidates,
636
and unknown when there are no candidates. D3C: day 3 control cell sample; D3B: day 3 biuret-
637
treated cell sample; D5C: day 5 control cell sample; D5B: day 5 biuret-treated cell sample.
638
639
Fig. 6 Free amino acids concentration (a) and allantoin concentration (b) in 8-day-old seedlings.
640
Rice plants were hydroponically grown under the control condition and 0.3 mmol L -1 biuret
641
toxicity. Five plants were combined for a single sample. Boxes indicate the mean of three samples,
30
642
and symbols indicate each sample. Asterisks indicate a statistically significant difference between
643
the treatments (Welch’s t-test). **p < 0.01; ***p < 0.001.
644
31
645
Supplemental Materials
646
Supplemental Fig. S1 Allantoin concentration in 9-day-old rice shoots measured by colorimetric
647
and HPLC-UV. Plants were grown hydroponically under the three biuret treatments. Control:
648
plants did not receive biuret; NB: plants were grown without biuret for three days after sowing,
649
and with 0.3 mmol L-1 biuret supplemented in the culture solution from the fourth day; BN: plants
650
were grown with 0.3 mmol L-1 biuret for 6 days after sowing and transferred to new culture
651
solution without biuret on the seventh day. Fresh shoots of 9-day-old seedlings were ground under
652
liquid N2 and extracted with 10-fold volume of distilled water. After centrifugation, the
653
supernatant was used for allantoin determination. Gray boxes indicate mean allantoin
654
concentration determined colorimetrically and black boxes indicate that determined by the HPLC
655
method. Symbols indicate each sample. The statistical significance of the differences between the
656
methods was determined through paired t-test (n = 2). ns: not significant.
657
658
Supplemental Fig. S2 Pictures of 9-day-old wild-type rice seedlings and two biuret hydrolase-
659
overexpressing lines. From left to right: wild type and overexpressing lines B3-9-1 and B2-3-3.
660
Upper: seedlings grown in the control culture solution. Lower: seedlings grown in the culture
661
solution supplemented with 0.3 mmol L-1 biuret. Bars show 10 cm.
662
663
Supplemental Fig. S3 Relative expression levels of (a) OsALN and (b) OsUO in 3 to 9-day-old
664
rice shoots in the preliminary experiment. Rice plants were hydroponically grown with or
665
without 0.3 mmol L-1 biuret supplied in the culture solution. Measurements were made using
666
plants grown in an independent trial from those shown in Figure 3. The relative expression
667
levels were normalized to those of Ubiquitin and Actin1 and expressed on a log2 scale. Gray
668
and black squares indicate control and biuret-treated plants, respectively; data represent the
32
669
mean ± SD (n = 4). Asterisks indicate statistically significant differences between treatments at
670
the time point (Welch’s t-test). *p < 0.05; **p < 0.01; ***p < 0.001. Numerical values above
671
asterisks indicate log2 fold-change relative to the control plants.
672
673
Supplemental Data S1 Peak intensities in Metabolome analysis.
674
33
Fig. 1 Effects of biuret on dry weight (a, d), biuret concentration (b, e), and allantoin concentration
(c, f) in roots and shoots of 7-day-old wild-type rice plants (a–c) and 9-day-old biuret hydrolaseoverexpressing rice lines (d–f). Bars and circles represent mean and each sample, respectively.
nd means not detected. (a–c) Wild-type plants were grown with 0, 0,1, and 0.3 mmol L-1 biuret
supplemented in the culture solution. Ten seedlings were combined for a single sample. Different
alphabets indicate significant difference among treatments in each organ (p < 0.05, Tukey’s test,
n = 3). (d–f) Wild-type and two independent transgenic lines (B3-9-1 and B2-3-3) were grown
with or without 0.3 mmol L-1 biuret in the culture solution. Four to six plants were combined into
one sample. Gray and black bars represent control and biuret-treated plants, respectively.
Asterisks indicate significant difference between the treatment (*p < 0.05; **p < 0.01, Welch’s ttest, n = 3). Different alphabets indicate significant difference in each organ (p < 0.05, Tukey’s
test, n = 3).
34
Fig. 2 Inhibitory effect of biuret for allantoinase activity. Crude extracts were prepared from
shoots of 9-day-old rice seedlings hydroponically grown without biuret. Extracts were incubated
at 30ºC with 10 mmol L-1 allantoin, 50 mmol L-1 Tricine-NaOH (pH8.0), 2mmol L-1 MnSO4,
and the desired concentration of biuret for 30min. The amount of allantoic acid produced from
allantoin was colorimetorically determined. Same shape symbols indicate a same crude extract.
Crossbars represent the mean value. The means were not significantly different among
treatments at 5% level (One-way ANOVA with blocking, n = 4).
35
Fig. 3 Relative expression of genes related to purine degradation and ureide metabolisms in roots
and shoots of 4 to 7-day old rice seedlings. Rice plants were hydroponically grown under the
control condition and 0.3 mmol L-1 biuret toxicity. Data obtained from two independent trials,
36
each with three replicates, are combined and shown. The relative expression levels of OsXO (a),
OsUO (b), OsALNS (c), OsALN (d), OsAAH (e), OsUGlyAH (f), OsUAH (g), OsUPS1 (h),
OsUPS2 (i), and OsUPS3 (j). The expression levels were normalized to the expression of
Ubiquitin and Actin1 and expressed in log2 scale. Gray and black symbols indicate control and
biuret treated samples, respectively. Crossbars indicate means of the six samples. Asterisks
indicate statistically significant difference between the treatments at the time point. *p < 0.05;
**p < 0.01; ***p < 0.001 (n = 6, Welch’s t-test). Numerical values above asterisks indicate log2
fold-change relative to the control plants.
37
Fig. 4 Principal component analysis of metabolomics profile of control and biuret-treated rice
suspension cells. Rice cells were transferred into a medium without biuret or with 0.3 mmol L -1
biuret and harvested 3 and 5 days after transfer. Closed symbols indicate control cells, and open
symbols indicate biuret-treated cells. Circles indicate day 3 samples, and triangles indicate day 5
samples.
38
Normalized intensity
ID
RT (sec)
m/z
Formula
D3C1 D3C2 D5C1 D5C2 D3B1 D3B2 D5B1 D5B2
47
37
102.0913
C5H11N1O1
-11
-11
-11
-11
239
54
170.0576
C4H12N1O4P1
-11
-11
-11
-11
-2
-1
-1
-1
310
55
176.1029
C6H13N3O3
326
56
159.0763
C6H10N2O3
342
57
120.0655
C4H9N1O3
372
58
138.0549
C7H7N1O2
432
58
268.0848
C9H17N1O6S1
-11
-11
-11
-11
-1
-1
448
59
385.1288
-11
-11
-11
-11
811
80
206.0480
C7H11N1O4S1
-11
-11
-11
-11
826
82
236.0585
C11H10N3O1Cl1
-11
-11
-11
-11
-3
864
83
238.0742
C8H15N1O5S1
-11
-11
-11
-11
-2
1100
99
284.1337
C10H21N1O8
-11
-11
-11
-11
1117
102
376.1283
-11
-11
-11
-11
1127
103
247.1286
C10H18N2O5
-11
-11
-11
-11
-2
1161
106
163.0599
C6H10O5
-11
-11
-11
1202
110
385.1287
-11
-11
-11
1240
114
387.1245
-11
-11
-11
-11
1247
114
136.0616
C5H5N5
-11
-11
-11
-11
-3
-1
1248
114
193.5696
Unknown Peak
-11
-11
-11
-11
1251
114
170.0651
Unknown Peak
-11
-11
-11
-11
1354
138
296.1160
C14H18N3O2Cl1
-1
-11
-11
-11
-1
-1
1719
263
529.1268
-11
-11
-11
-11
1722
264
190.1072
1805
278
285.0901
-11
-11
-11
-11
1867
292
149.1171
C7H16O3
-11
-11
-11
-11
-1
1954
309
304.1389
C13H21N1O7
2067
322
229.1545
C11H20N2O3
-11
-11
-11
-1
2219
339
352.1389
C17H21N1O7
-11
-11
-11
2222
339
445.0944
-11
-11
-11
-11
2340
360
587.2546
-1
-11
-11
-11
-1
2444
386
293.1164
-11
-11
-11
-11
2470
394
159.1014
-11
-11
-11
-11
2476
395
335.1334
2477
395
370.1706
2669
487
141.1273
-11
-11
-11
-11
2837
645
1118.7230
-4
-11
-11
-11
-3
-3
-2
-2
3022
806
522.3552
C26H52N1O7P1
-1
-11
-11
-11
-2
3183
965
487.3603
Unknown Peak
-1
-1
-1
-1
-11
-11
-11
-2
C8H15N1O4
C8H14O3
C9H16O1
Fig. 5 Normalized peak intensities of differentially accumulated metabolites between control
and biuret treated rice suspension cells. Peaks with significantly different intensity between the
control-group and biuret-group are shown in the list (p < 0.05, Welch’s t-test, n = 4). RT column
indicate retention time in second. In the formula column, the formula is shown when the
formula is uniquely determined from the m/z value, blank when there are multiple possible
candidates, and unknown when there are no candidates. D3C: day 3 control cell sample; D3B:
day 3 biuret-treated cell sample; D5C: day 5 control cell sample; D5B: day 5 biuret-treated cell
sample.
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Fig. 6 Free amino acids concentration (a) and allantoin concentration (b) in 8-day-old seedlings.
Rice plants were hydroponically grown under the control condition and 0.3 mmol L -1 biuret
toxicity. Five plants were combined for a single sample. Boxes indicate the mean of three samples,
and symbols indicate each sample. Asterisks indicate a statistically significant difference between
the treatments (Welch’s t-test). **p < 0.01; ***p < 0.001.
40
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