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. 1998 Jan;116(1):299-307.
doi: 10.1104/pp.116.1.299.

Metabolism of polyamines in transgenic cells of carrot expressing a mouse ornithine decarboxylase cDNA

S C Andersen  1 , D R Bastola, S C Minocha
Affiliations

Metabolism of polyamines in transgenic cells of carrot expressing a mouse ornithine decarboxylase cDNA

S C Andersen et al. Plant Physiol. 1998 Jan.

Abstract

The metabolisms of arginine (Arg), ornithine (Orn), and putrescine were compared in a nontransgenic and a transgenic cell line of carrot (Daucus carota L.) expressing a mouse Orn decarboxylase cDNA. [14C]Arg, [14C]Orn, and [14C]putrescine were fed to cells and their rates of decarboxylation, uptake, metabolism into polyamines, and incorporation into acid-insoluble material were determined. Transgenic cells showed higher decarboxylation rates for labeled Orn than the nontransgenic cells. This was correlated positively with higher amounts of labeled putrescine production from labeled Orn. With labeled Arg, both the transgenic and the nontransgenic cells exhibited similar rates of decarboxylation and conversion into labeled putrescine. When [14C]putrescine was fed, higher rates of degradation were observed in transgenic cells as compared with the nontransgenic cells. It is concluded that (a) increased production of putrescine via the Orn decarboxylase pathway has no compensatory effects on the Arg decarboxylase pathway, and (b) higher rates of putrescine production in the transgenic cells are accompanied by higher rates of putrescine conversion into spermidine and spermine as well as the catabolism of putrescine.

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Figures

Figure 1
Figure 1
Polyamine biosynthetic pathway in plants (Slocum, 1991).
Figure 2
Figure 2
The rates of 14CO2 production from [U-14C]Orn (A) and [U-14C]Arg (B) in nontransgenic (NT) and transgenic (ODC-N14) carrot cells during a 4-h incubation period. Values are means ± se of three replicates. Different lowercase letters indicate that the values are significantly different (P ≤ 0.05) from each other at a given time. FW, Fresh weight.
Figure 3
Figure 3
The incorporation of [U-14C]Orn into labeled putrescine (A and B), spermidine (C and D), and spermine (E and F) in nontransgenic (NT) and transgenic (ODC-N14) carrot cells during a 24-h incubation period. Dansylated polyamines were separated on TLC and radioactivity was counted after elution of bands. The data for 0 to 4 h and 4 to 24 h were taken from two separate experiments. Values are means ± se of three replicates. Different lowercase letters indicate that the values are significantly different (P ≤ 0.05) from each other at a given time. FW, Fresh weight.
Figure 4
Figure 4
The incorporation of [U-14C]Arg into labeled putrescine (A and B), spermidine (C and D), and spermine (E and F) in nontransgenic (NT) and transgenic (ODC-N14) carrot cells during a 24-h incubation period. Dansylated polyamines were separated on TLC and radioactivity was counted after elution of bands. The data for 0 to 4 h and 4 to 24 h were taken from two separate experiments. Values are means ± se of three replicates. Different lowercase letters indicate that the values are significantly different (P ≤ 0.05) from each other at a given time. FW, Fresh weight.
Figure 5
Figure 5
The amounts of label from [U-14C] Orn (A) and [U-14C]Arg (B) present in the aqueous fraction (remaining after the removal of dansyl-polyamines by toluene) in nontransgenic (NT) and transgenic (ODC-N14) carrot cells during a 4-h incubation period. Values are means ± se of three replicates. Different lowercase letters indicate that the values are significantly different (P ≤ 0.05) from each other at a given time. FW, Fresh weight.
Figure 6
Figure 6
The incorporation of [U-14C]Orn (A) and [U-14C]Arg (B) into acid-insoluble material in nontransgenic (NT) and transgenic (ODC-N14) carrots cells during a 4-h incubation period. Values are means ± se of three replicates. Different lowercase letters indicate that the values are significantly different (P ≤ 0.05) from each other at a given time. FW, Fresh weight.
Figure 7
Figure 7
The amount of 14CO2 released (A), 14C present in the acid-insoluble fraction (B), and 14C present in the dansyl-polyamine fraction from [1,4-14C]putrescine (C) in nontransgenic (NT) and transgenic (ODC-N14) carrot cells during a 4-h incubation period. Values are means ± se of three replicates. Different lowercase letters indicate that the values are significantly different (P ≤ 0.05) from each other at a given time. FW, Fresh weight.
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