Abstract
Phosphatidic acid (PtdOH) is emerging as an important signaling lipid in abiotic stress responses in plants. The effect of cold stress was monitored using (32)P-labeled seedlings and leaf discs of Arabidopsis thaliana. Low, non-freezing temperatures were found to trigger a very rapid (32)P-PtdOH increase, peaking within 2 and 5 min, respectively. In principle, PtdOH can be generated through three different pathways, i.e., (1) via de novo phospholipid biosynthesis (through acylation of lyso-PtdOH), (2) via phospholipase D hydrolysis of structural phospholipids, or (3) via phosphorylation of diacylglycerol (DAG) by DAG kinase (DGK). Using a differential (32)P-labeling protocol and a PLD-transphosphatidylation assay, evidence is provided that the rapid (32)P-PtdOH response was primarily generated through DGK. A simultaneous decrease in the levels of (32)P-PtdInsP, correlating in time, temperature dependency, and magnitude with the increase in (32)P-PtdOH, suggested that a PtdInsP-hydrolyzing PLC generated the DAG in this reaction. Testing T-DNA insertion lines available for the seven DGK genes, revealed no clear changes in (32)P-PtdOH responses, suggesting functional redundancy. Similarly, known cold-stress mutants were analyzed to investigate whether the PtdOH response acted downstream of the respective gene products. The hos1, los1, and fry1 mutants were found to exhibit normal PtdOH responses. Slight changes were found for ice1, snow1, and the overexpression line Super-ICE1, however, this was not cold-specific and likely due to pleiotropic effects. A tentative model illustrating direct cold effects on phospholipid metabolism is presented.
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Claims 6
Claim · model-written summary
Low non-freezing temperatures triggered a very rapid increase in (32)P-PtdOH in Arabidopsis, peaking within 2 and 5 min.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianae0 - Treatment
- Low, non-freezing temperaturese1
- Outcome
- (32)P-PtdOHe1
- Direction
- increasee1
- Qualifier
- peaking within 2 and 5 min, respectivelye1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The effect of cold stress was monitored using (32)P-labeled seedlings and leaf discs of Arabidopsis thaliana”
e1“Low, non-freezing temperatures were found to trigger a very rapid (32)P-PtdOH increase, peaking within 2 and 5 min, respectively”
Claim · model-written summary
The simultaneous decrease in (32)P-PtdInsP correlated in time, temperature dependency and magnitude with the increase in (32)P-PtdOH.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Compound
- (32)P-PtdOHe2
- Outcome
- (32)P-PtdInsPe2
- Direction
- decreasee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The effect of cold stress was monitored using (32)P-labeled seedlings and leaf discs of Arabidopsis thaliana”
e2“A simultaneous decrease in the levels of (32)P-PtdInsP, correlating in time, temperature dependency, and magnitude with the increase in (32)P-PtdOH”
Claim · model-written summary
A PtdInsP-hydrolyzing PLC is suggested to generate the DAG in the cold-induced PtdOH reaction.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Gene
- PtdInsP-hydrolyzing PLCe2
- Outcome
- generated the DAGe2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The effect of cold stress was monitored using (32)P-labeled seedlings and leaf discs of Arabidopsis thaliana”
e2“suggested that a PtdInsP-hydrolyzing PLC generated the DAG in this reaction”
Claim · model-written summary
The rapid (32)P-PtdOH response is primarily generated through DGK.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Gene
- DGKe3
- Outcome
- rapid (32)P-PtdOH responsee3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The effect of cold stress was monitored using (32)P-labeled seedlings and leaf discs of Arabidopsis thaliana”
e3“evidence is provided that the rapid (32)P-PtdOH response was primarily generated through DGK”
Claim · model-written summary
T-DNA insertion lines for the seven DGK genes showed no clear change in (32)P-PtdOH responses, suggesting functional redundancy.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Treatment
- T-DNA insertion linese4
- Gene
- DGK genese4
- Outcome
- (32)P-PtdOH responsese4
- Direction
- no_changeinferrede4
- Qualifier
- suggesting functional redundancye4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The effect of cold stress was monitored using (32)P-labeled seedlings and leaf discs of Arabidopsis thaliana”
e4“Testing T-DNA insertion lines available for the seven DGK genes, revealed no clear changes in (32)P-PtdOH responses, suggesting functional redundancy”
Claim · model-written summary
Slight changes were found for ice1, snow1 and the Super-ICE1 overexpression line, not specific to cold.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Material
- the overexpression line Super-ICE1e6
- Gene
- ice1, snow1e6
- Outcome
- changese6
- Qualifier
- not cold-specific and likely due to pleiotropic effectse6
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The effect of cold stress was monitored using (32)P-labeled seedlings and leaf discs of Arabidopsis thaliana”
e6“Slight changes were found for ice1, snow1, and the overexpression line Super-ICE1, however, this was not cold-specific and likely due to pleiotropic effects”