Abstract
During drought stress, cellular proteostasis on the one hand and amino acid homeostasis on the other hand are severely challenged, because the decrease in photosynthesis induces massive proteolysis, leading to drastic changes in both the proteome and the free amino acid pool. Thus, we selected progressive drought stress in Arabidopsis (Arabidopsis thaliana) as a model to investigate on a quantitative level the balance between protein and free amino acid homeostasis. We analyzed the mass composition of the leaf proteome based on proteomics datasets, and estimated how many protein molecules are present in a plant cell and its subcellular compartments. In addition, we calculated stress-induced changes in the distribution of individual amino acids between the free and protein-bound pools. Under control conditions, an average Arabidopsis mesophyll cell contains about 25 billion protein molecules, of which 80% are localized in chloroplasts. Severe water deficiency leads to degradation of more than 40% of the leaf protein mass, and thus causes a drastic shift in distribution toward the free amino acid pool. Stress-induced proteolysis of just half of the 340 million RubisCO hexadecamers present in the chloroplasts of a single mesophyll cell doubles the cellular content of free amino acids. A major fraction of the amino acids released from proteins is channeled into synthesis of proline, which is a compatible osmolyte. Complete oxidation of the remaining fraction as an alternative respiratory substrate can fully compensate for the lack of photosynthesis-derived carbohydrates for several hours.
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Claims 7
Claim · model-written summary
An average Arabidopsis mesophyll cell contains about 25 billion protein molecules under control conditions.
- Taxon
- Arabidopsis
Arabidopsise0 - Organ / stage
- mesophyll celle0
- Outcome
- protein moleculese0
- Value
- about 25 billione0
- Qualifier
- Under control conditionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under control conditions, an average Arabidopsis mesophyll cell contains about 25 billion protein molecules”
Claim · model-written summary
Eighty percent of protein molecules in an average Arabidopsis mesophyll cell are in chloroplasts under control conditions.
- Taxon
- ArabidopsisArabidopsise0
- Organ / stage
- chloroplastse0
- Outcome
- protein moleculese0
- Value
- 80%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under control conditions, an average Arabidopsis mesophyll cell contains about 25 billion protein molecules, of which 80% are localized in chloroplasts”
Claim · model-written summary
Severe water deficiency degrades more than 40% of Arabidopsis leaf protein mass.
- Taxon
- ArabidopsisArabidopsise1
- Treatment
- Severe water deficiencye0
- Outcome
- leaf protein masse0
- Direction
- degradatione0
- Value
- more than 40%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Severe water deficiency leads to degradation of more than 40% of the leaf protein mass”
e1“Arabidopsis (Arabidopsis thaliana)”
Claim · model-written summary
Severe water deficiency shifts amino acid distribution toward the free amino acid pool.
- Taxon
- ArabidopsisArabidopsise1
- Treatment
- Severe water deficiencye0
- Outcome
- distribution toward the free amino acid poole0
- Direction
- shifte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Severe water deficiency leads to degradation of more than 40% of the leaf protein mass, and thus causes a drastic shift in distribution toward the free amino acid pool”
e1“Arabidopsis (Arabidopsis thaliana)”
Claim · model-written summary
Proteolysis of half of the 340 million RubisCO hexadecamers doubles cellular free amino acids.
- Taxon
- ArabidopsisArabidopsise1
- Organ / stage
- chloroplastse0
- Gene
- RubisCOe0
- Outcome
- cellular content of free amino acidse0
- Direction
- doublese0
- Value
- half of the 340 million RubisCO hexadecamerse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Stress-induced proteolysis of just half of the 340 million RubisCO hexadecamers present in the chloroplasts of a single mesophyll cell doubles the cellular content of free amino acids”
e1“Arabidopsis (Arabidopsis thaliana)”
Claim · model-written summary
A major fraction of amino acids released from proteins is channeled into proline synthesis.
- Taxon
- ArabidopsisArabidopsise1
- Outcome
- synthesis of prolinee0
- Qualifier
- A major fractione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A major fraction of the amino acids released from proteins is channeled into synthesis of proline”
e1“Arabidopsis (Arabidopsis thaliana)”
Claim · model-written summary
Complete oxidation of remaining amino acids could compensate for missing photosynthesis-derived carbohydrates for several hours.
- Taxon
- ArabidopsisArabidopsise1
- Outcome
- lack of photosynthesis-derived carbohydratese0
- Value
- several hourse0
- Qualifier
- Complete oxidation of the remaining fractione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Complete oxidation of the remaining fraction as an alternative respiratory substrate can fully compensate for the lack of photosynthesis-derived carbohydrates for several hours”
e1“Arabidopsis (Arabidopsis thaliana)”
The same questions in other papers
drought · quality: protein · ArabidopsisPositive and negative results
2 papers in the same direction as this paper · 1 in the opposite direction
- positive
- no effect
- no effect
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.