Abstract
Membrane disruption has been proposed to be a key event in plant senescence, and phospholipase D (PLD; EC 3.1.4.4) has been thought to play an important role in membrane deterioration. We recently cloned and biochemically characterized three different PLDs from Arabidopsis. In this study, we investigated the role of the most prevalent phospholipid-hydrolyzing enzyme, PLD alpha, in membrane degradation and senescence in Arabidopsis. The expression of PLD alpha was suppressed by introducing a PLD alpha antisense cDNA fragment into Arabidopsis. When incubated with abscisic acid and ethylene, leaves detached from the PLD alpha-deficient transgenic plants showed a slower rate of senescence than did those from wild-type and transgenic control plants. The retardation of senescence was demonstrated by delayed leaf yellowing, lower ion leakage, greater photosynthetic activity, and higher content of chlorophyll and phospholipids in the PLD alpha antisense leaves than in those of the wild type. Treatment of detached leaves with abscisic acid and ethylene stimulated PLD alpha expression, as indicated by increases in PLD alpha mRNA, protein, and activity. In the absence of abscisic acid and ethylene, however, detached leaves from the PLD alpha-deficient and wild-type plants showed a similar rate of senescence. In addition, the suppression of PLD alpha did not alter natural plant growth and development. These data suggest that PLD alpha is an important mediator in phytohormone-promoted senescence in detached leaves but is not a direct promoter of natural senescence. The physiological relevance of these findings is discussed.
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Claims 10
Claim · model-written summary
PLD alpha-deficient leaves senesced more slowly than controls under ABA and ethylene.
- Taxon
- Arabidopsis
Arabidopsist0 - Organ / stage
- leavese0
- Treatment
- abscisic acid and ethylenee0
- Gene
- PLD alphae0
- Outcome
- rate of senescencee0
- Direction
- slowere0
- Comparator
- wild-type and transgenic control plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When incubated with abscisic acid and ethylene, leaves detached from the PLD alpha-deficient transgenic plants showed a slower rate of senescence than did those from wild-type and transgenic control plants”
t0“Arabidopsis leaves”
Claim · model-written summary
PLD alpha antisense leaves had delayed yellowing.
- Taxon
- ArabidopsisArabidopsist0
- Organ / stage
- leafe0
- Outcome
- leaf yellowinge0
- Direction
- delayede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“delayed leaf yellowing”
t0“Arabidopsis leaves”
Claim · model-written summary
PLD alpha antisense leaves had lower ion leakage.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- ion leakagee0
- Direction
- lowere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“lower ion leakage”
t0“Arabidopsis leaves”
Claim · model-written summary
PLD alpha antisense leaves had greater photosynthetic activity.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- photosynthetic activitye0
- Direction
- greatere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“greater photosynthetic activity”
t0“Arabidopsis leaves”
Claim · model-written summary
PLD alpha antisense leaves had higher chlorophyll content.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- content of chlorophylle0
- Direction
- highere0
- Comparator
- wild typee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“higher content of chlorophyll and phospholipids in the PLD alpha antisense leaves than in those of the wild type”
t0“Arabidopsis leaves”
Claim · model-written summary
PLD alpha antisense leaves had higher phospholipid content.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- phospholipidse0
- Direction
- highere0
- Comparator
- wild typee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“higher content of chlorophyll and phospholipids in the PLD alpha antisense leaves than in those of the wild type”
t0“Arabidopsis leaves”
Claim · model-written summary
ABA and ethylene increased PLD alpha mRNA, protein, and activity in detached leaves.
- Taxon
- ArabidopsisArabidopsist0
- Organ / stage
- detached leavese0
- Treatment
- abscisic acid and ethylenee0
- Gene
- PLD alphae0
- Outcome
- PLD alpha mRNA, protein, and activitye0
- Direction
- increasese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Treatment of detached leaves with abscisic acid and ethylene stimulated PLD alpha expression, as indicated by increases in PLD alpha mRNA, protein, and activity”
t0“Arabidopsis leaves”
Claim · model-written summary
Without ABA and ethylene, deficient and wild-type leaves had similar senescence rates.
- Taxon
- ArabidopsisArabidopsist0
- Organ / stage
- detached leavese0
- Treatment
- absence of abscisic acid and ethylenee0
- Outcome
- rate of senescencee0
- Direction
- similare0
- Comparator
- wild-type plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the absence of abscisic acid and ethylene, however, detached leaves from the PLD alpha-deficient and wild-type plants showed a similar rate of senescence”
t0“Arabidopsis leaves”
Claim · model-written summary
PLD alpha suppression did not alter natural growth and development.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- suppression of PLD alphae0
- Gene
- PLD alphae0
- Outcome
- natural plant growth and developmente0
- Direction
- did not altere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the suppression of PLD alpha did not alter natural plant growth and development”
t0“Arabidopsis leaves”
Claim · model-written summary
PLD alpha was interpreted as a mediator of hormone-promoted senescence but not natural senescence.
- Taxon
- ArabidopsisArabidopsist0
- Gene
- PLD alphae0
- Outcome
- phytohormone-promoted senescence in detached leavese0
- Qualifier
- not a direct promoter of natural senescencee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“PLD alpha is an important mediator in phytohormone-promoted senescence in detached leaves but is not a direct promoter of natural senescence”
t0“Arabidopsis leaves”
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