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Background
Eucalyptus is the main timber species, most of which are hybrid clones, and usually grow in aluminized acid soil in China. The exudation of organic acids from roots may contribute to detoxification of Al and lead to the Al-tolerance in Eucalyptus genotypes. To further understand the organic acid response in Al tolerance in Eucalyptus, the Al-tolerant Eucalyptus grandis × E. urophylla clone GL-9 (marked as “G9”) and the Al-sensitive Eucalyptus urophylla clone GL-4 (marked as “W4”) were used to investigate the secretion and metabolism of citrate and malate in roots.
Results
Eucalyptus seedlings in hydroponics were exposed to the presence or absence of 4.4 mM Al at pH 4.0 for 24 hours. The protein synthesis inhibitor cycloheximide (CHM) and the anion channel blocker phenylglyoxal (PG) were applied to explore possible pathways involved in organic acid secretion. The Al treatments caused higher Al accumulation in roots of both clones. The secretion of malate and citrate was greater in G9 than in W4, corresponding to the relatively higher tolerance in G9 to Al. The peak Al concentration occurred after 1 h in G9 roots and declined afterward, indicating the activation of detoxification to alleviate Al accumulation. After 6 h of Al exposure, the efflux of citrate dramatically increased in G9 after a substantial lag phase, while both peak Al accumulation in roots and peak malate secretion occurred and there was no induction of citrate secretion in W4. Enhanced activity for citrate synthase and phosphoenolpyruvate carboxylase, and reduced activity for NADP-isocitrate dehydrogenase, aconitase and NADP-malic enzyme were closely associated with the greater secretion of citrate in G9. Both PG and CHM were effective inhibitors of citrate and malate secretion in both Eucalyptus clones, except the malate secretion in W4 was not affected by CHM.
Conclusions
In two different Al-tolerant Eucalyptus clones, both secretion and internal accumulation of citrate and malate in roots were involved in Al detoxification. An anion channel on the plasma membrane could be an important mode of organic acid secretion. Citrate and relevant metabolizing enzymes led more important role in the response to Al in E. grandis × E. urophylla.
Keywords
Eucalyptus, aluminum tolerance, citrate, malate, metabolizing enzymes
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CURRENT STATUS: Published
View the published article at BMC Plant Biology.
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Editorial decision: Accept
On 07 Dec, 2020
Editor assigned
On 06 Dec, 2020
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On 06 Dec, 2020
Editor invited
On 06 Dec, 2020
Version (no preprint)
Posted 30 Nov, 2020
Editor assigned
On 30 Nov, 2020
Submission checks complete
On 30 Nov, 2020
Editor invited
On 30 Nov, 2020
This version was not preprinted
No comments provided
Editorial decision: Minor revision
On 17 Nov, 2020
Review #3 received
Received 01 Nov, 2020
Review #2 received
Received 22 Oct, 2020
Reviewer #3 agreed
On 14 Oct, 2020
Review #1 received
Received 14 Oct, 2020
Reviewers invited
Invitations sent on 13 Oct, 2020
Reviewer #1 agreed
On 13 Oct, 2020
Reviewer #2 agreed
On 13 Oct, 2020
Editor assigned
On 11 Oct, 2020
Submission checks complete
On 10 Oct, 2020
Editor invited
On 10 Oct, 2020
Version 1
Posted 28 May, 2020
No comments provided
Editorial decision: Major revision
On 27 Aug, 2020
Review #4 received
Received 06 Aug, 2020
Review #3 received
Received 26 Jul, 2020
Review #2 received
Received 26 Jul, 2020
Reviewer #4 agreed
On 23 Jul, 2020
Reviewer #2 agreed
On 22 Jul, 2020
Reviewer #3 agreed
On 22 Jul, 2020
Review #1 received
Received 03 Jul, 2020
Reviewer #1 agreed
On 15 Jun, 2020
Reviewers invited
Invitations sent on 15 Jun, 2020
Editor assigned
On 15 May, 2020
First submitted
On 14 May, 2020
Submission checks complete
On 14 May, 2020
Editor invited
On 14 May, 2020
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A new preprint design is coming!
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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
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.
No community comments so far
Editorial decision: Accept
On 07 Dec, 2020
Editor assigned
On 06 Dec, 2020
Submission checks complete
On 06 Dec, 2020
Editor invited
On 06 Dec, 2020
Version (no preprint)
Posted 30 Nov, 2020
Editor assigned
On 30 Nov, 2020
Submission checks complete
On 30 Nov, 2020
Editor invited
On 30 Nov, 2020
This version was not preprinted
No comments provided
Editorial decision: Minor revision
On 17 Nov, 2020
Review #3 received
Received 01 Nov, 2020
Review #2 received
Received 22 Oct, 2020
Reviewer #3 agreed
On 14 Oct, 2020
Review #1 received
Received 14 Oct, 2020
Reviewers invited
Invitations sent on 13 Oct, 2020
Reviewer #1 agreed
On 13 Oct, 2020
Reviewer #2 agreed
On 13 Oct, 2020
Editor assigned
On 11 Oct, 2020
Submission checks complete
On 10 Oct, 2020
Editor invited
On 10 Oct, 2020
Version 1
Posted 28 May, 2020
No comments provided
Editorial decision: Major revision
On 27 Aug, 2020
Review #4 received
Received 06 Aug, 2020
Review #3 received
Received 26 Jul, 2020
Review #2 received
Received 26 Jul, 2020
Reviewer #4 agreed
On 23 Jul, 2020
Reviewer #2 agreed
On 22 Jul, 2020
Reviewer #3 agreed
On 22 Jul, 2020
Review #1 received
Received 03 Jul, 2020
Reviewer #1 agreed
On 15 Jun, 2020
Reviewers invited
Invitations sent on 15 Jun, 2020
Editor assigned
On 15 May, 2020
First submitted
On 14 May, 2020
Submission checks complete
On 14 May, 2020
Editor invited
On 14 May, 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
Eucalyptus is the main timber species, most of which are hybrid clones, and usually grow in aluminized acid soil in China. The exudation of organic acids from roots may contribute to detoxification of Al and lead to the Al-tolerance in Eucalyptus genotypes. To further understand the organic acid response in Al tolerance in Eucalyptus, the Al-tolerant Eucalyptus grandis × E. urophylla clone GL-9 (marked as “G9”) and the Al-sensitive Eucalyptus urophylla clone GL-4 (marked as “W4”) were used to investigate the secretion and metabolism of citrate and malate in roots.
Results
Eucalyptus seedlings in hydroponics were exposed to the presence or absence of 4.4 mM Al at pH 4.0 for 24 hours. The protein synthesis inhibitor cycloheximide (CHM) and the anion channel blocker phenylglyoxal (PG) were applied to explore possible pathways involved in organic acid secretion. The Al treatments caused higher Al accumulation in roots of both clones. The secretion of malate and citrate was greater in G9 than in W4, corresponding to the relatively higher tolerance in G9 to Al. The peak Al concentration occurred after 1 h in G9 roots and declined afterward, indicating the activation of detoxification to alleviate Al accumulation. After 6 h of Al exposure, the efflux of citrate dramatically increased in G9 after a substantial lag phase, while both peak Al accumulation in roots and peak malate secretion occurred and there was no induction of citrate secretion in W4. Enhanced activity for citrate synthase and phosphoenolpyruvate carboxylase, and reduced activity for NADP-isocitrate dehydrogenase, aconitase and NADP-malic enzyme were closely associated with the greater secretion of citrate in G9. Both PG and CHM were effective inhibitors of citrate and malate secretion in both Eucalyptus clones, except the malate secretion in W4 was not affected by CHM.
Conclusions
In two different Al-tolerant Eucalyptus clones, both secretion and internal accumulation of citrate and malate in roots were involved in Al detoxification. An anion channel on the plasma membrane could be an important mode of organic acid secretion. Citrate and relevant metabolizing enzymes led more important role in the response to Al in E. grandis × E. urophylla.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
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