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Research article
Gábor Galiba
Corresponding Author
ORCiD: https://orcid.org/0000-0001-7504-935X
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This work is licensed under a CC BY 4.0 License. Read Full License
Background Over the life cycle of perennial trees, the dormant state enables the avoidance of abiotic stress conditions. The growth cycle can be partitioned into induction, maintenance and release and is controlled by complex interactions between many endogenous and environmental factors. While phytohormones have long been linked with dormancy, there is increasing evidence of regulation by DAM and CBF genes. To reveal whether the expression kinetics of CBFs and their target PtDAM1 is related to growth cessation and endodormancy induction in Populus, two hybrid poplar cultivars were studied which had known differential responses to dormancy inducing conditions.
Results Growth cessation, dormancy status and expression of six PtCBFs and PtDAM1 were analyzed. The ‘Okanese’ hybrid cultivar ceased growth rapidly, was able to reach endodormancy, and exhibited a significant increase of several PtCBF transcripts in the buds on the 10th day. The ‘Walker’ cultivar had delayed growth cessation, was unable to enter endodormancy, and showed much lower CBF expression in buds. Expression of PtDAM1 peaked on the 10th day only in the buds of ‘Okanese’. In addition, PtDAM1 was not expressed in the leaves of either cultivar while leaf CBFs expression pattern was several fold higher in ‘Walker’, peaking at day 1. Leaf phytohormones in both cultivars followed similar profiles during growth cessation but differentiated based on cytokinins which were largely reduced, while the Ox-IAA and iP7G increased in ‘Okanese’ compared to ‘Walker’. Surprisingly, ABA concentration was reduced in leaves of both cultivars. However, the metabolic deactivation product of ABA, phaseic acid, exhibited an early peak on the first day in ‘Okanese’.
Conclusions Our results indicate that PtCBFs and PtDAM1 have differential kinetics and spatial localization which may be related to early growth cessation and endodormancy induction under the regime of low night temperature and short photoperiod in poplar. Unlike buds, PtCBFs and PtDAM1 expression levels in leaves were not associated with early growth cessation and dormancy induction under these conditions. Our study provides new evidence that the degradation of auxin and cytokinins in leaves may be an important regulatory point in a CBF-DAM induced endodormancy. Further investigation of other PtDAMs in bud tissue and a study of both growth-inhibiting and the degradation of growth-promoting phytohormones is warranted.
Keywords
Endodormancy, growth cessation, PtCBFs, PtDAM1, gene expression, plant hormone, degradation, Populus
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This is a list of supplementary files associated with this preprint. Click to download.
- SupplementedFigure.docx
- SuppTableS1.pdf
Supplemented Table 1 Sequences, melting temperatures and GC contents of the primers used in the study. All the primer sequences listed, with exception of PtDAM1, were collected from the work of Menon et al. (2015) [58].
- SuppTable2CBFexp.xlsx
Supplemented Table 2 Raw relative gene expression data of the CBF genes.
- SuppTable3hormones.xlsx
Supplemented Table 3 Raw data of hormone analysis.
- SuppFigure01.pdf
Supplemented Figure 1 Relative expression levels in buds (panel A-E) and in leaves (panel F-K) of the PtCBF1, PtCBF2, PtCBF3, PtCBF4, PtCBF5 and PtCBF6 genes in the Okanese (black bars) and Walker (white bars) genotypes. The expression levels were determined by the ΔΔCt method. Pt18S rRNA gene was used as a housekeeping gene for normalization. Mean expression values were normalized per the expression level at the zero sampling time-point, separately for each genotype. The expression values are presented in log2 scale. Error bars represent the ±SEM originating from 3 biological and 3 technical replicates. ‘nd’: the expression level was undetectable.
- SuppFigure02.png
Supplemented Figure 2 Heatmap of the combined phytohormone concentration in leaves (L) and expression of CBFs and DAM genes (leaves (L) and buds (B)) in ‘Okanese’ (Ok) and ‘Walker’ (Wa) poplar hybrid cultivars over the 60-day short photoperiod and low night temperature growth cessation/dormancy induction treatment. The heatmap was clustered by Euclidean distance. The color bars and letters represent the hierarchy between the investigate gene expression and hormone compound levels.
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CURRENT STATUS: Published
View the published article at BMC Plant Biology.
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Posted 15 Jan, 2021
No community comments so far
Submission checks complete
On 08 Jan, 2021
Editorial decision: Accept
On 05 Jan, 2021
No comments provided
Editorial decision: Minor revision
On 20 Dec, 2020
Review #2 received
Received 19 Dec, 2020
Review #1 received
Received 02 Dec, 2020
Reviewer #2 agreed
On 29 Nov, 2020
Reviewer #1 agreed
On 29 Nov, 2020
Reviewers invited
Invitations sent on 26 Nov, 2020
Editor assigned
On 25 Nov, 2020
Submission checks complete
On 25 Nov, 2020
Editor invited
On 25 Nov, 2020
No comments provided
Editorial decision: Major revision
On 28 Oct, 2020
Review #2 received
Received 27 Oct, 2020
Reviewer #2 agreed
On 10 Oct, 2020
Review #1 received
Received 24 Sep, 2020
Reviewers invited
Invitations sent on 03 Sep, 2020
Reviewer #1 agreed
On 03 Sep, 2020
Editor assigned
On 20 Aug, 2020
Submission checks complete
On 19 Aug, 2020
Editor invited
On 19 Aug, 2020
First submitted
On 18 Aug, 2020
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See the published version of this preprint at BMC Plant Biology.
This is a preprint, a preliminary version of a manuscript that has not completed peer review at a journal. Research Square does not conduct peer review prior to posting preprints. The posting of a preprint on this server should not be interpreted as an endorsement of its validity or suitability for dissemination as established information or for guiding clinical practice.
Learn more about In Review
Research article
Gábor Galiba
Corresponding Author
ORCiD: https://orcid.org/0000-0001-7504-935X
Badges
Prescreen
This manuscript passed our Prescreen assessment
Complete author information
Appropriate declaration statements
Potential risks to human health
Prescreen
Peer Review Timeline
CURRENT STATUS: Published
View the published article at BMC Plant Biology.
Version 3
Posted 15 Jan, 2021
No community comments so far
Submission checks complete
On 08 Jan, 2021
Editorial decision: Accept
On 05 Jan, 2021
No comments provided
Editorial decision: Minor revision
On 20 Dec, 2020
Review #2 received
Received 19 Dec, 2020
Review #1 received
Received 02 Dec, 2020
Reviewer #2 agreed
On 29 Nov, 2020
Reviewer #1 agreed
On 29 Nov, 2020
Reviewers invited
Invitations sent on 26 Nov, 2020
Editor assigned
On 25 Nov, 2020
Submission checks complete
On 25 Nov, 2020
Editor invited
On 25 Nov, 2020
No comments provided
Editorial decision: Major revision
On 28 Oct, 2020
Review #2 received
Received 27 Oct, 2020
Reviewer #2 agreed
On 10 Oct, 2020
Review #1 received
Received 24 Sep, 2020
Reviewers invited
Invitations sent on 03 Sep, 2020
Reviewer #1 agreed
On 03 Sep, 2020
Editor assigned
On 20 Aug, 2020
Submission checks complete
On 19 Aug, 2020
Editor invited
On 19 Aug, 2020
First submitted
On 18 Aug, 2020
Metrics
Comments: 0
PDF Downloads: ...
HTML Views: ...
License:
This work is licensed under a CC BY 4.0 License. Read Full License
View the published article at BMC Plant Biology.
Background Over the life cycle of perennial trees, the dormant state enables the avoidance of abiotic stress conditions. The growth cycle can be partitioned into induction, maintenance and release and is controlled by complex interactions between many endogenous and environmental factors. While phytohormones have long been linked with dormancy, there is increasing evidence of regulation by DAM and CBF genes. To reveal whether the expression kinetics of CBFs and their target PtDAM1 is related to growth cessation and endodormancy induction in Populus, two hybrid poplar cultivars were studied which had known differential responses to dormancy inducing conditions.
Results Growth cessation, dormancy status and expression of six PtCBFs and PtDAM1 were analyzed. The ‘Okanese’ hybrid cultivar ceased growth rapidly, was able to reach endodormancy, and exhibited a significant increase of several PtCBF transcripts in the buds on the 10th day. The ‘Walker’ cultivar had delayed growth cessation, was unable to enter endodormancy, and showed much lower CBF expression in buds. Expression of PtDAM1 peaked on the 10th day only in the buds of ‘Okanese’. In addition, PtDAM1 was not expressed in the leaves of either cultivar while leaf CBFs expression pattern was several fold higher in ‘Walker’, peaking at day 1. Leaf phytohormones in both cultivars followed similar profiles during growth cessation but differentiated based on cytokinins which were largely reduced, while the Ox-IAA and iP7G increased in ‘Okanese’ compared to ‘Walker’. Surprisingly, ABA concentration was reduced in leaves of both cultivars. However, the metabolic deactivation product of ABA, phaseic acid, exhibited an early peak on the first day in ‘Okanese’.
Conclusions Our results indicate that PtCBFs and PtDAM1 have differential kinetics and spatial localization which may be related to early growth cessation and endodormancy induction under the regime of low night temperature and short photoperiod in poplar. Unlike buds, PtCBFs and PtDAM1 expression levels in leaves were not associated with early growth cessation and dormancy induction under these conditions. Our study provides new evidence that the degradation of auxin and cytokinins in leaves may be an important regulatory point in a CBF-DAM induced endodormancy. Further investigation of other PtDAMs in bud tissue and a study of both growth-inhibiting and the degradation of growth-promoting phytohormones is warranted.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
This is a list of supplementary files associated with this preprint. Click to download.
- SupplementedFigure.docx
- SuppTableS1.pdf
Supplemented Table 1 Sequences, melting temperatures and GC contents of the primers used in the study. All the primer sequences listed, with exception of PtDAM1, were collected from the work of Menon et al. (2015) [58].
- SuppTable2CBFexp.xlsx
Supplemented Table 2 Raw relative gene expression data of the CBF genes.
- SuppTable3hormones.xlsx
Supplemented Table 3 Raw data of hormone analysis.
- SuppFigure01.pdf
Supplemented Figure 1 Relative expression levels in buds (panel A-E) and in leaves (panel F-K) of the PtCBF1, PtCBF2, PtCBF3, PtCBF4, PtCBF5 and PtCBF6 genes in the Okanese (black bars) and Walker (white bars) genotypes. The expression levels were determined by the ΔΔCt method. Pt18S rRNA gene was used as a housekeeping gene for normalization. Mean expression values were normalized per the expression level at the zero sampling time-point, separately for each genotype. The expression values are presented in log2 scale. Error bars represent the ±SEM originating from 3 biological and 3 technical replicates. ‘nd’: the expression level was undetectable.
- SuppFigure02.png
Supplemented Figure 2 Heatmap of the combined phytohormone concentration in leaves (L) and expression of CBFs and DAM genes (leaves (L) and buds (B)) in ‘Okanese’ (Ok) and ‘Walker’ (Wa) poplar hybrid cultivars over the 60-day short photoperiod and low night temperature growth cessation/dormancy induction treatment. The heatmap was clustered by Euclidean distance. The color bars and letters represent the hierarchy between the investigate gene expression and hormone compound levels.
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