Abstract
BACKGROUND: Oilseed rape is the third largest oleaginous crop in the world but requires high levels of N fertilizer of which only 50% is recovered in seeds. This weak N use efficiency is associated with a low foliar N remobilization, leading to a significant return of N to the soil and a risk of pollution. Contrary to what is observed during senescence in the vegetative stages, N remobilization from stems and leaves is considered efficient during monocarpic senescence. However, the contribution of stems towards N management and the cellular mechanisms involved in foliar remobilization remain largely unknown. To reach this goal, the N fluxes at the whole plant level from bolting to mature seeds and the processes involved in leaf N remobilization and proteolysis were investigated in two contrasting genotypes (Aviso and Oase) cultivated under ample or restricted nitrate supply. RESULTS: During seed filling in both N conditions, Oase efficiently allocated the N from uptake to seeds while Aviso favoured a better N remobilization from stems and leaves towards seeds. Nitrate restriction decreased seed yield and oil quality for both genotypes but Aviso had the best seed N filling. Under N limitation, Aviso had a better N remobilization from leaves to stems before the onset of seed filling. Afterwards, the higher N remobilization from stems and leaves of Aviso led to a higher final N amount in seeds. This high leaf N remobilization is associated with a better degradation/export of insoluble proteins, oligopeptides, nitrate and/or ammonia. By using an original method based on the determination of Rubisco degradation in the presence of inhibitors of proteases, efficient proteolysis associated with cysteine proteases and proteasome activities was identified as the mechanism of N remobilization. CONCLUSION: The results confirm the importance of foliar N remobilization after bolting to satisfy seed filling and highlight that an efficient proteolysis is mainly associated with (i) cysteine proteases and proteasome activities and (ii) a fine coordination between proteolysis and export mechanisms. In addition, the stem may act as transient storage organs in the case of an asynchronism between leaf N remobilization and N demand for seed filling.
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Claims 10
Claim · model-written summary
Oase efficiently allocated nitrogen from uptake to seeds under both nitrogen conditions.
- Taxon
- Oilseed rape
_Brassica_napus_-_Habit.jpg?width=60)
Brassica napust0 - Material
- Oasee0
- Outcome
- N from uptake to seedse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
_Brassica_napus_-_Habit.jpg?width=500)
Verbatim
e0“During seed filling in both N conditions, Oase efficiently allocated the N from uptake to seeds”
t0“Oilseed rape”
Claim · model-written summary
Aviso remobilized nitrogen from stems and leaves toward seeds more effectively.
- Taxon
- Oilseed rapeBrassica napust0
- Material
- Avisoe0
- Outcome
- N remobilization from stems and leaves towards seedse0
- Direction
- bettere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Aviso favoured a better N remobilization from stems and leaves towards seeds”
t0“Oilseed rape”
Claim · model-written summary
Nitrate restriction decreased seed yield in both genotypes.
- Taxon
- Oilseed rapeBrassica napust0
- Treatment
- Nitrate restrictione0
- Outcome
- seed yielde0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrate restriction decreased seed yield and oil quality for both genotypes”
t0“Oilseed rape”
Claim · model-written summary
Nitrate restriction decreased oil quality in both genotypes.
- Taxon
- Oilseed rapeBrassica napust0
- Treatment
- Nitrate restrictione0
- Outcome
- oil qualitye0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrate restriction decreased seed yield and oil quality for both genotypes”
t0“Oilseed rape”
Claim · model-written summary
Aviso had the best seed nitrogen filling under nitrate restriction.
- Taxon
- Oilseed rapeBrassica napust0
- Material
- Avisoe0
- Outcome
- seed N fillinge0
- Direction
- beste0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Aviso had the best seed N filling”
t0“Oilseed rape”
Claim · model-written summary
Under nitrogen limitation, Aviso remobilized more nitrogen from leaves to stems before seed filling.
- Taxon
- Oilseed rapeBrassica napust0
- Material
- Avisoe0
- Outcome
- N remobilization from leaves to stemse0
- Direction
- bettere0
- Qualifier
- before the onset of seed fillinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under N limitation, Aviso had a better N remobilization from leaves to stems before the onset of seed filling”
t0“Oilseed rape”
Claim · model-written summary
Aviso later remobilized more nitrogen from stems and leaves, yielding more final seed nitrogen.
- Taxon
- Oilseed rapeBrassica napust0
- Material
- Avisoe0
- Outcome
- final N amount in seedse0
- Direction
- highere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the higher N remobilization from stems and leaves of Aviso led to a higher final N amount in seeds”
t0“Oilseed rape”
Claim · model-written summary
High leaf nitrogen remobilization was associated with better degradation and export of insoluble proteins, oligopeptides, nitrate and/or ammonia.
- Taxon
- Oilseed rapeBrassica napust0
- Organ / stage
- leafe0
- Outcome
- leaf N remobilizatione0
- Direction
- highe0
- Qualifier
- better degradation/export of insoluble proteins, oligopeptides, nitrate and/or ammoniae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This high leaf N remobilization is associated with a better degradation/export of insoluble proteins, oligopeptides, nitrate and/or ammonia”
t0“Oilseed rape”
Claim · model-written summary
Cysteine protease and proteasome activity were identified as mechanisms of efficient proteolysis in nitrogen remobilization.
- Taxon
- Oilseed rapeBrassica napust0
- Gene
- cysteine proteases and proteasomee0
- Outcome
- N remobilizatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“efficient proteolysis associated with cysteine proteases and proteasome activities was identified as the mechanism of N remobilization”
t0“Oilseed rape”
Claim · model-written summary
The stem may transiently store nitrogen when leaf remobilization and seed nitrogen demand are asynchronous.
- Taxon
- Oilseed rapeBrassica napust0
- Organ / stage
- steme0
- Outcome
- transient storage organse0
- Qualifier
- asynchronism between leaf N remobilization and N demand for seed fillinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the stem may act as transient storage organs in the case of an asynchronism between leaf N remobilization and N demand for seed filling”
t0“Oilseed rape”
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