Abstract
Phosphate is an essential nutrient. In most soils it is limiting, which has resulted in that phosphate is supplied as fertilizer to increase crop yield. Through evolution, plants have adapted several mechanisms to increase phosphate uptake from the soil and to household with acquired phosphate. A recent discovered house-holding mechanism is that plants utilize the phosphate bound in the headgroups of phospholipids: under phosphate-limiting conditions, phospholipids can be replaced by the non-phosphate containing lipid digalactosyldiacylglycerol (DGDG), previously assumed to reside in plastid membranes. The extra-plastidial phospholipid-to-DGDG replacement occurs in plasma membrane, tonoplast and mitochondria and has led to discoveries of new enzymes and metabolic pathways in plants. This thesis reports that phosphate limitation-induced biochemical and lipid compositional changes in oat root plasma membranes occur prior to any morphological changes in the oat. The phospholipase kinetics suggests that the plasma membrane is continuously supplied with phospholipids and that the products of plasma membrane lipase activities, phosphatidic acid and diacylglycerol, both are removed from the membrane. Furthermore, the phospholipid-to-DGDG replacement is reversible and when phosphate is resupplied the proportion of phospholipids increases and DGDG decreases in the oat root plasma membrane. Membrane lipids are more than a two dimensional liquid where membrane proteins reside. The specific lipid composition and distribution enables the membrane to function as a barrier to solutes and the interactions between lipids and proteins are important for the correct function. The lateral and transversal lipid distribution in oat root plasma membranes shows that DGDG does not replace phospholipids molecule for molecule; whereas phospholipids occur in both leaflets of the plasma membrane, DGDG is almost exclusively localized in the cytosolic leaflet. Model membrane studies suggests that one of the reasons that DGDG is absent in the apoplastic leaflet is its incompatibility to properly interact with the high sterol content of this leaflet. The oat seed contains enough phosphate to complete an entire generation without any exogenously supplied phosphate. The overall seed yield is much lower in phosphate-limited oat compared to fully fertilized oat, but the seed quality (starch, [beta]-glucan, lipid, soluble protein) is very similar, including that the phospholipids-to-DGDG replacement is absent from the mature oat seeds, here membrane lipid composition is conserved. Oat thus produce a few seeds of acceptable quality rather than more seeds of poor quality.
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Claims 11
Claim · model-written summary
Phosphate limitation induced biochemical and lipid compositional changes before morphological changes.
- Taxon
- oat
Avena sativae0 - Organ / stage
- root plasma membranese0
- Outcome
- biochemical and lipid compositional changes in oat root plasma membranese0
- Qualifier
- prior to any morphological changese0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“phosphate limitation-induced biochemical and lipid compositional changes in oat root plasma membranes occur prior to any morphological changes in the oat.”
Claim · model-written summary
Phospholipase kinetics suggested continuous phospholipid supply to the plasma membrane and removal of phosphatidic acid and diacylglycerol.
- Taxon
- OatsAvena sativat0
- Organ / stage
- plasma membranee0
- Outcome
- plasma membrane is continuously supplied with phospholipidse0
- Qualifier
- phospholipase kineticse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The phospholipase kinetics suggests that the plasma membrane is continuously supplied with phospholipids and that the products of plasma membrane lipase activities, phosphatidic acid and diacylglycerol, both are removed from the membrane.”
t0“Oats”
Claim · model-written summary
Resupplying phosphate increased phospholipid proportion in oat root plasma membrane.
- Taxon
- oatAvena sativae0
- Organ / stage
- root plasma membranee0
- Treatment
- phosphate is resuppliede0
- Outcome
- proportion of phospholipidse0
- Direction
- increasese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“when phosphate is resupplied the proportion of phospholipids increases and DGDG decreases in the oat root plasma membrane.”
Claim · model-written summary
Resupplying phosphate decreased DGDG proportion in oat root plasma membrane.
- Taxon
- oatAvena sativae0
- Organ / stage
- root plasma membranee0
- Treatment
- phosphate is resuppliede0
- Outcome
- DGDGe0
- Direction
- decreasese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“when phosphate is resupplied the proportion of phospholipids increases and DGDG decreases in the oat root plasma membrane.”
Claim · model-written summary
DGDG did not replace phospholipids molecule for molecule in root plasma membranes.
- Taxon
- oatAvena sativae0
- Organ / stage
- root plasma membranese0
- Outcome
- DGDG does not replace phospholipids molecule for moleculee0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The lateral and transversal lipid distribution in oat root plasma membranes shows that DGDG does not replace phospholipids molecule for molecule”
Claim · model-written summary
Phospholipids occurred in both membrane leaflets, whereas DGDG was nearly confined to the cytosolic leaflet.
- Taxon
- oatAvena sativae1
- Organ / stage
- plasma membranee0
- Outcome
- DGDG is almost exclusively localized in the cytosolic leaflete0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“whereas phospholipids occur in both leaflets of the plasma membrane, DGDG is almost exclusively localized in the cytosolic leaflet.”
e1“oat root plasma membranes shows that DGDG”
Claim · model-written summary
Model membranes suggested DGDG exclusion from the apoplastic leaflet reflects incompatibility with its high sterol content.
- Taxon
- OatsAvena sativat0
- Outcome
- DGDG is absent in the apoplastic leaflete0
- Qualifier
- incompatibility to properly interact with the high sterol content of this leaflete0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Model membrane studies suggests that one of the reasons that DGDG is absent in the apoplastic leaflet is its incompatibility to properly interact with the high sterol content of this leaflet.”
t0“Oats”
Claim · model-written summary
Oat seed phosphate reserves could support an entire generation without external phosphate.
- Taxon
- oatAvena sativae0
- Organ / stage
- seede0
- Outcome
- enough phosphate to complete an entire generatione0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The oat seed contains enough phosphate to complete an entire generation without any exogenously supplied phosphate.”
Claim · model-written summary
Phosphate-limited oats produced much lower overall seed yield than fully fertilized oats.
- Taxon
- oatAvena sativae0
- Treatment
- phosphate-limitede0
- Outcome
- overall seed yielde0
- Direction
- much lowere0
- Comparator
- fully fertilized oate0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The overall seed yield is much lower in phosphate-limited oat compared to fully fertilized oat”
Claim · model-written summary
Seed starch, beta-glucan, lipid and soluble protein quality was very similar under phosphate limitation and full fertilization.
- Taxon
- oatAvena sativae1
- Treatment
- phosphate-limitede1
- Outcome
- seed quality (starch, [beta]-glucan, lipid, soluble protein)e0
- Direction
- very similare0
- Comparator
- fully fertilized oate1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“but the seed quality (starch, [beta]-glucan, lipid, soluble protein) is very similar”
e1“phosphate-limited oat compared to fully fertilized oat”
Claim · model-written summary
Mature oat seeds did not show phospholipid-to-DGDG replacement.
- Taxon
- oatAvena sativae0
- Organ / stage
- mature oat seedse0
- Outcome
- phospholipids-to-DGDG replacement is absente0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the phospholipids-to-DGDG replacement is absent from the mature oat seeds”
The same questions in other papers
phosphorus · yield · Avena sativa (oats)Results differ
22 papers in the same direction as this paper · 4 in the opposite direction
This paper is about lacking the nutrient, so it counts the other way round here.
- no effect
- negative
- no effect
23 papers more in this group
See all 27 papers →phosphorus · physiology: osmolytes · Avena sativa (oats)Positive and negative results
1 in the opposite direction
This paper is about lacking the nutrient, so it counts the other way round here.
- positive
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.