Abstract
Despite its relevance, protein regulation, metabolic adjustment, and the physiological status of plants under drought is not well understood in relation to the role of nitrogen fixation in nodules. In this study, nodulated alfalfa plants were exposed to drought conditions. The study determined the physiological, metabolic, and proteomic processes involved in photosynthetic inhibition in relation to the decrease in nitrogenase (N(ase)) activity. The deleterious effect of drought on alfalfa performance was targeted towards photosynthesis and N(ase) activity. At the leaf level, photosynthetic inhibition was mainly caused by the inhibition of Rubisco. The proteomic profile and physiological measurements revealed that the reduced carboxylation capacity of droughted plants was related to limitations in Rubisco protein content, activation state, and RuBP regeneration. Drought also decreased amino acid content such as asparagine, and glutamic acid, and Rubisco protein content indicating that N availability limitations were caused by N(ase) activity inhibition. In this context, drought induced the decrease in Rubisco binding protein content at the leaf level and proteases were up-regulated so as to degrade Rubisco protein. This degradation enabled the reallocation of the Rubisco-derived N to the synthesis of amino acids with osmoregulant capacity. Rubisco degradation under drought conditions was induced so as to remobilize Rubisco-derived N to compensate for the decrease in N associated with N(ase) inhibition. Metabolic analyses showed that droughted plants increased amino acid (proline, a major compound involved in osmotic regulation) and soluble sugar (D-pinitol) levels to contribute towards the decrease in osmotic potential (Ψ(s)). At the nodule level, drought had an inhibitory effect on N(ase) activity. This decrease in N(ase) activity was not induced by substrate shortage, as reflected by an increase in total soluble sugars (TSS) in the nodules. Proline accumulation in the nodule could also be associated with an osmoregulatory response to drought and might function as a protective agent against ROS. In droughted nodules, the decrease in N(2) fixation was caused by an increase in oxygen resistance that was induced in the nodule. This was a mechanism to avoid oxidative damage associated with reduced respiration activity and the consequent increase in oxygen content. This study highlighted that even though drought had a direct effect on leaves, the deleterious effects of drought on nodules also conditioned leaf responsiveness.
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Claims 17
Claim · model-written summary
Drought had a deleterious effect on alfalfa photosynthesis and nitrogenase activity.
- Taxon
- alfalfa
Medicago sativat0 - Treatment
- droughte1
- Outcome
- photosynthesis and N(ase) activitye1
- Direction
- deleterious effecte1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The deleterious effect of drought on alfalfa performance was targeted towards photosynthesis and N(ase) activity”
t0“in alfalfa (Medicago sativa L.)”
Claim · model-written summary
Photosynthetic inhibition in drought-stressed alfalfa leaves was mainly caused by inhibition of Rubisco.
- Taxon
- alfalfaMedicago sativat0
- Organ / stage
- leaf levele1
- Gene
- Rubiscoe1
- Outcome
- photosynthetic inhibitione1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“At the leaf level, photosynthetic inhibition was mainly caused by the inhibition of Rubisco”
t0“in alfalfa (Medicago sativa L.)”
Claim · model-written summary
The reduced carboxylation capacity of droughted alfalfa was related to limits in Rubisco protein content, activation state and RuBP regeneration.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- droughted plantse1
- Gene
- Rubiscoe1
- Outcome
- carboxylation capacitye1
- Direction
- reducede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“the reduced carboxylation capacity of droughted plants was related to limitations in Rubisco protein content, activation state, and RuBP regeneration”
t0“in alfalfa (Medicago sativa L.)”
Claim · model-written summary
Drought decreased amino acid content such as asparagine and glutamic acid in alfalfa.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- droughte1
- Outcome
- amino acid content such as asparagine, and glutamic acide1
- Direction
- decreasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Drought also decreased amino acid content such as asparagine, and glutamic acid, and Rubisco protein content indicating that N availability limitations were caused by N(ase) activity inhibition”
t0“in alfalfa (Medicago sativa L.)”
Claim · model-written summary
Drought decreased Rubisco protein content in alfalfa.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- droughte1
- Gene
- Rubiscoe1
- Outcome
- Rubisco protein contente1
- Direction
- decreasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Drought also decreased amino acid content such as asparagine, and glutamic acid, and Rubisco protein content indicating that N availability limitations were caused by N(ase) activity inhibition”
t0“in alfalfa (Medicago sativa L.)”
Claim · model-written summary
N availability limitations in droughted alfalfa are caused by inhibition of N(ase) activity.
- Taxon
- alfalfaMedicago sativat0
- Gene
- N(ase)e1
- Outcome
- N availability limitationse1
- Qualifier
- N(ase) activity inhibitione1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Drought also decreased amino acid content such as asparagine, and glutamic acid, and Rubisco protein content indicating that N availability limitations were caused by N(ase) activity inhibition”
t0“in alfalfa (Medicago sativa L.)”
Claim · model-written summary
Drought decreased Rubisco binding protein content at the leaf level of alfalfa.
- Taxon
- alfalfaMedicago sativat0
- Organ / stage
- leaf levele1
- Treatment
- droughte1
- Gene
- Rubisco binding proteine1
- Outcome
- Rubisco binding protein contente1
- Direction
- decreasee1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In this context, drought induced the decrease in Rubisco binding protein content at the leaf level”
t0“in alfalfa (Medicago sativa L.)”
Claim · model-written summary
Proteases were up-regulated under drought in alfalfa leaves.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- droughte1
- Gene
- proteasese2
- Outcome
- proteasese2
- Direction
- up-regulatede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In this context, drought induced the decrease in Rubisco binding protein content at the leaf level”
e2“proteases were up-regulated so as to degrade Rubisco protein”
t0“in alfalfa (Medicago sativa L.)”
Claim · model-written summary
Rubisco degradation releases Rubisco-derived N for amino acids with osmoregulant capacity in alfalfa.
- Taxon
- alfalfaMedicago sativat0
- Gene
- Rubiscoe1
- Outcome
- reallocation of the Rubisco-derived Ne1
- Qualifier
- osmoregulant capacitye1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“This degradation enabled the reallocation of the Rubisco-derived N to the synthesis of amino acids with osmoregulant capacity”
t0“in alfalfa (Medicago sativa L.)”
Claim · model-written summary
Amino acid levels (proline) increased in droughted alfalfa.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- droughted plantse1
- Outcome
- amino acid (proline, a major compound involved in osmotic regulation)e1
- Direction
- increasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Metabolic analyses showed that droughted plants increased amino acid (proline, a major compound involved in osmotic regulation) and soluble sugar (D-pinitol) levels to contribute towards the decrease in osmotic potential”
t0“in alfalfa (Medicago sativa L.)”
Claim · model-written summary
Soluble sugar (D-pinitol) levels increased in droughted alfalfa.
- Taxon
- alfalfaMedicago sativat0
- Treatment
- droughted plantse1
- Outcome
- soluble sugar (D-pinitol)e1
- Direction
- increasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Metabolic analyses showed that droughted plants increased amino acid (proline, a major compound involved in osmotic regulation) and soluble sugar (D-pinitol) levels to contribute towards the decrease in osmotic potential”
t0“in alfalfa (Medicago sativa L.)”
Claim · model-written summary
Proline and D-pinitol accumulation contributes to the decrease in osmotic potential of droughted alfalfa.
- Taxon
- alfalfaMedicago sativat0
- Outcome
- osmotic potentiale1
- Qualifier
- contribute towards the decrease in osmotic potentiale1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Metabolic analyses showed that droughted plants increased amino acid (proline, a major compound involved in osmotic regulation) and soluble sugar (D-pinitol) levels to contribute towards the decrease in osmotic potential”
t0“in alfalfa (Medicago sativa L.)”
Claim · model-written summary
Drought had an inhibitory effect on nitrogenase activity in alfalfa nodules.
- Taxon
- alfalfaMedicago sativat0
- Organ / stage
- nodule levele1
- Treatment
- droughte1
- Gene
- N(ase)e1
- Outcome
- N(ase) activitye1
- Direction
- inhibitory effecte1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“At the nodule level, drought had an inhibitory effect on N(ase) activity”
t0“in alfalfa (Medicago sativa L.)”
Claim · model-written summary
Total soluble sugars increased in nodules of droughted alfalfa, so substrate shortage did not cause the decrease in nitrogenase activity.
- Taxon
- alfalfaMedicago sativat0
- Organ / stage
- nodulese1
- Outcome
- total soluble sugars (TSS)e1
- Direction
- an increasee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“This decrease in N(ase) activity was not induced by substrate shortage, as reflected by an increase in total soluble sugars (TSS) in the nodules”
t0“in alfalfa (Medicago sativa L.)”
Claim · model-written summary
Proline accumulation in nodules may protect against ROS under drought.
- Taxon
- alfalfaMedicago sativat0
- Organ / stage
- nodulee1
- Outcome
- Proline accumulatione1
- Qualifier
- might function as a protective agent against ROSe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“Proline accumulation in the nodule could also be associated with an osmoregulatory response to drought and might function as a protective agent against ROS”
t0“in alfalfa (Medicago sativa L.)”
Claim · model-written summary
The decrease in nitrogen fixation in droughted nodules is caused by an increase in oxygen resistance.
- Taxon
- alfalfaMedicago sativat0
- Organ / stage
- droughted nodulese1
- Outcome
- decrease in N(2) fixatione1
- Qualifier
- an increase in oxygen resistancee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In droughted nodules, the decrease in N(2) fixation was caused by an increase in oxygen resistance that was induced in the nodule”
t0“in alfalfa (Medicago sativa L.)”
Claim · model-written summary
Deleterious effects of drought on nodules condition leaf responsiveness in alfalfa.
- Taxon
- alfalfaMedicago sativat0
- Organ / stage
- nodulese1
- Treatment
- the deleterious effects of drought on nodulese1
- Outcome
- leaf responsivenesse1
- Direction
- conditionede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“This study highlighted that even though drought had a direct effect on leaves, the deleterious effects of drought on nodules also conditioned leaf responsiveness”
t0“in alfalfa (Medicago sativa L.)”
The same questions in other papers
drought · physiology: photosynthesis · Medicago sativa (alfalfa)Positive and negative results
11 papers in the same direction as this paper · 3 in the opposite direction
- positive
- no effect
- negative
11 papers more in this group
See all 15 papers →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.