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The Arabidopsis plastid-signalling mutant gun1 (genomes uncoupled1) shows altered sensitivity to sucrose and abscisic acid and alterations in early seedling development.

Cottage A, Mott EK, Kempster JA, Gray JC - J. Exp. Bot. (2010)

Bottom Line: Norflurazon and lincomycin, which induce retrograde signalling, further decreased the anthocyanin content of sucrose-treated seedlings, and altered the temporal pattern of anthocyanin accumulation.Lincomycin treatment altered the spatial pattern of sucrose-induced anthocyanin accumulation, suggesting that plastids provide information for the regulation of anthocyanin biosynthesis in Arabidopsis seedlings.Growth and development of gun1 seedlings was more sensitive to exogenous 2% sucrose than wild-type seedlings and, in the presence of lincomycin, cotyledon expansion was enhanced in gun1 seedlings compared to the wild type. gun1 seedlings were more sensitive than wild-type seedlings to the inhibition of seedling growth and development by abscisic acid.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.

ABSTRACT
Developing seedlings of the Arabidopsis gun1 (genomes uncoupled1) mutant, which is defective in retrograde plastid-to-nucleus signalling, show several previously unrecognized mutant phenotypes. gun1 seedlings accumulated less anthocyanin than wild-type seedlings when grown in the presence of 2% (w/v) sucrose, due to lower amounts of transcripts of early anthocyanin biosynthesis genes in gun1. Norflurazon and lincomycin, which induce retrograde signalling, further decreased the anthocyanin content of sucrose-treated seedlings, and altered the temporal pattern of anthocyanin accumulation. Lincomycin treatment altered the spatial pattern of sucrose-induced anthocyanin accumulation, suggesting that plastids provide information for the regulation of anthocyanin biosynthesis in Arabidopsis seedlings. The temporal pattern of accumulation of LHCB1 transcripts differed between wild-type and gun1 seedlings, and gun1 seedlings were more sensitive to sucrose suppression of LHCB1 transcript accumulation than wild-type seedlings. Growth and development of gun1 seedlings was more sensitive to exogenous 2% sucrose than wild-type seedlings and, in the presence of lincomycin, cotyledon expansion was enhanced in gun1 seedlings compared to the wild type. gun1 seedlings were more sensitive than wild-type seedlings to the inhibition of seedling growth and development by abscisic acid. These observations clearly implicate GUN1 and plastid signalling in the regulation of seedling development and anthocyanin biosynthesis, and indicate a complex interplay between sucrose and plastid signalling pathways.

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Time-course of LHCB1 transcript abundance in wild-type and gun1 seedlings. RT-PCRs were performed on three replicate samples of RNA extracted from 3–8-d-old wild-type (Col-0) and gun1-1 seedlings grown on 0.5× MS-agar medium, ±2% sucrose (suc), and ±0.5 mM lincomycin (Linc). The PCR products are shown in the upper part of the figure. The amounts of LHCB1 PCR product normalized to those of ACT7 are shown in the lower part of the figure. The ratios are expressed as mean ±standard error for the three independent RT-PCRs analysed for each treatment.
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fig7: Time-course of LHCB1 transcript abundance in wild-type and gun1 seedlings. RT-PCRs were performed on three replicate samples of RNA extracted from 3–8-d-old wild-type (Col-0) and gun1-1 seedlings grown on 0.5× MS-agar medium, ±2% sucrose (suc), and ±0.5 mM lincomycin (Linc). The PCR products are shown in the upper part of the figure. The amounts of LHCB1 PCR product normalized to those of ACT7 are shown in the lower part of the figure. The ratios are expressed as mean ±standard error for the three independent RT-PCRs analysed for each treatment.

Mentions: Because the gun1 mutation altered the temporal accumulation of anthocyanin in the presence of sucrose (Fig. 4), the time-course of LHCB1 transcript accumulation was examined in 3–8-d-old gun1 and wild-type seedlings grown in the presence or absence of sucrose and lincomycin (Fig. 7). Three replicate samples of RNA were analysed at each time point, and the whole experiment was repeated four times. Reproducible differences in the patterns of LHCB1 transcript abundance were observed between gun1 and wild-type seedlings, although the rapid decrease in LHCB1 transcript abundance in gun1, seen on day 6 in the absence of sucrose in Fig. 7, was observed to occur on day 5 in some experiments. In the absence of sucrose, wild-type seedlings contained very low amounts of LHCB1 transcripts on day 3, and showed maximal LHCB1 transcripts on day 4, followed by a slow decline over the next 4 d (Fig. 7, left panel). In gun1 seedlings in the absence of sucrose, LHCB1 transcripts reached a maximum on day 4 but, unlike wild-type seedlings, LHCB1 transcripts were already present at a high level on day 3. Transcripts then declined sharply, followed by an increase on day 7 (Fig. 7 right panel). Sucrose repressed LHCB1 in both gun1 and wild-type seedlings. There were reproducible fluctuations in the amounts of LHCB1 transcripts in both sets of seedlings over the period day 4 to day 8, with the pattern in gun1 seedlings appearing to be a mirror image of the pattern in wild-type seedlings. This indicates that the temporal pattern of LHCB1 regulation by sucrose is perturbed in gun1 seedlings.


The Arabidopsis plastid-signalling mutant gun1 (genomes uncoupled1) shows altered sensitivity to sucrose and abscisic acid and alterations in early seedling development.

Cottage A, Mott EK, Kempster JA, Gray JC - J. Exp. Bot. (2010)

Time-course of LHCB1 transcript abundance in wild-type and gun1 seedlings. RT-PCRs were performed on three replicate samples of RNA extracted from 3–8-d-old wild-type (Col-0) and gun1-1 seedlings grown on 0.5× MS-agar medium, ±2% sucrose (suc), and ±0.5 mM lincomycin (Linc). The PCR products are shown in the upper part of the figure. The amounts of LHCB1 PCR product normalized to those of ACT7 are shown in the lower part of the figure. The ratios are expressed as mean ±standard error for the three independent RT-PCRs analysed for each treatment.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2921207&req=5

fig7: Time-course of LHCB1 transcript abundance in wild-type and gun1 seedlings. RT-PCRs were performed on three replicate samples of RNA extracted from 3–8-d-old wild-type (Col-0) and gun1-1 seedlings grown on 0.5× MS-agar medium, ±2% sucrose (suc), and ±0.5 mM lincomycin (Linc). The PCR products are shown in the upper part of the figure. The amounts of LHCB1 PCR product normalized to those of ACT7 are shown in the lower part of the figure. The ratios are expressed as mean ±standard error for the three independent RT-PCRs analysed for each treatment.
Mentions: Because the gun1 mutation altered the temporal accumulation of anthocyanin in the presence of sucrose (Fig. 4), the time-course of LHCB1 transcript accumulation was examined in 3–8-d-old gun1 and wild-type seedlings grown in the presence or absence of sucrose and lincomycin (Fig. 7). Three replicate samples of RNA were analysed at each time point, and the whole experiment was repeated four times. Reproducible differences in the patterns of LHCB1 transcript abundance were observed between gun1 and wild-type seedlings, although the rapid decrease in LHCB1 transcript abundance in gun1, seen on day 6 in the absence of sucrose in Fig. 7, was observed to occur on day 5 in some experiments. In the absence of sucrose, wild-type seedlings contained very low amounts of LHCB1 transcripts on day 3, and showed maximal LHCB1 transcripts on day 4, followed by a slow decline over the next 4 d (Fig. 7, left panel). In gun1 seedlings in the absence of sucrose, LHCB1 transcripts reached a maximum on day 4 but, unlike wild-type seedlings, LHCB1 transcripts were already present at a high level on day 3. Transcripts then declined sharply, followed by an increase on day 7 (Fig. 7 right panel). Sucrose repressed LHCB1 in both gun1 and wild-type seedlings. There were reproducible fluctuations in the amounts of LHCB1 transcripts in both sets of seedlings over the period day 4 to day 8, with the pattern in gun1 seedlings appearing to be a mirror image of the pattern in wild-type seedlings. This indicates that the temporal pattern of LHCB1 regulation by sucrose is perturbed in gun1 seedlings.

Bottom Line: Norflurazon and lincomycin, which induce retrograde signalling, further decreased the anthocyanin content of sucrose-treated seedlings, and altered the temporal pattern of anthocyanin accumulation.Lincomycin treatment altered the spatial pattern of sucrose-induced anthocyanin accumulation, suggesting that plastids provide information for the regulation of anthocyanin biosynthesis in Arabidopsis seedlings.Growth and development of gun1 seedlings was more sensitive to exogenous 2% sucrose than wild-type seedlings and, in the presence of lincomycin, cotyledon expansion was enhanced in gun1 seedlings compared to the wild type. gun1 seedlings were more sensitive than wild-type seedlings to the inhibition of seedling growth and development by abscisic acid.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.

ABSTRACT
Developing seedlings of the Arabidopsis gun1 (genomes uncoupled1) mutant, which is defective in retrograde plastid-to-nucleus signalling, show several previously unrecognized mutant phenotypes. gun1 seedlings accumulated less anthocyanin than wild-type seedlings when grown in the presence of 2% (w/v) sucrose, due to lower amounts of transcripts of early anthocyanin biosynthesis genes in gun1. Norflurazon and lincomycin, which induce retrograde signalling, further decreased the anthocyanin content of sucrose-treated seedlings, and altered the temporal pattern of anthocyanin accumulation. Lincomycin treatment altered the spatial pattern of sucrose-induced anthocyanin accumulation, suggesting that plastids provide information for the regulation of anthocyanin biosynthesis in Arabidopsis seedlings. The temporal pattern of accumulation of LHCB1 transcripts differed between wild-type and gun1 seedlings, and gun1 seedlings were more sensitive to sucrose suppression of LHCB1 transcript accumulation than wild-type seedlings. Growth and development of gun1 seedlings was more sensitive to exogenous 2% sucrose than wild-type seedlings and, in the presence of lincomycin, cotyledon expansion was enhanced in gun1 seedlings compared to the wild type. gun1 seedlings were more sensitive than wild-type seedlings to the inhibition of seedling growth and development by abscisic acid. These observations clearly implicate GUN1 and plastid signalling in the regulation of seedling development and anthocyanin biosynthesis, and indicate a complex interplay between sucrose and plastid signalling pathways.

Show MeSH
Related in: MedlinePlus