title: The contrasting N management of two oilseed rape genotypes reveals the mechanisms of proteolysis associated with leaf N remobilization and the respective contributions of leaves and stems to N storage and remobilization during seed filling.
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.
  
  
  CONCLUSIONS
  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.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Girondé
authors.forename: Philippe
authors.initials: P
authors.lastname: Etienne
authors.forename: Jacques
authors.initials: J
authors.lastname: Trouverie
authors.forename: Alain
authors.initials: A
authors.lastname: Bouchereau
authors.forename: Françoise
authors.initials: F
authors.lastname: Le Cahérec
authors.forename: Laurent
authors.initials: L
authors.lastname: Leport
authors.forename: Mathilde
authors.initials: M
authors.lastname: Orsel
authors.forename: Marie-Françoise
authors.initials: MF
authors.lastname: Niogret
authors.forename: Nathalie
authors.initials: N
authors.lastname: Nesi
authors.forename: Deleu
authors.initials: D
authors.lastname: Carole
authors.forename: Fabienne
authors.initials: F
authors.lastname: Soulay
authors.forename: Céline
authors.initials: C
authors.lastname: Masclaux-Daubresse
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Avice
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D018533:Biomass; D029688:Brassica napus / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D005838:Genotype; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D007700:Kinetics; D009566:Nitrates / Q000494:pharmacology; D009584:Nitrogen / Q000378:metabolism* / Q000494:pharmacology; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism*; D010938:Plant Oils / Q000378:metabolism*; D018547:Plant Stems / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology; D059748:Proteolysis / Q000187:drug effects; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism; D012639:Seeds / Q000187:drug effects / Q000378:metabolism*; D012995:Solubility
chemical_list: D000596:Amino Acids; D009566:Nitrates; D010938:Plant Oils; D011480:Protease Inhibitors; D002734:Chlorophyll; D005969:Glutamate Dehydrogenase; D012273:Ribulose-Bisphosphate Carboxylase; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen
references.citation: Plant Mol Biol. 1999 Feb;39(3):395-405
references.pmid: 10092169
references.citation: Planta. 2000 Sep;211(4):510-8
references.pmid: 11030550
references.citation: Planta. 2000 Nov;211(6):833-40
references.pmid: 11144268
references.citation: J Exp Bot. 2001 Aug;52(361):1655-63
references.pmid: 11479330
references.citation: Anal Biochem. 2002 Feb 1;301(1):91-6
references.pmid: 11811971
references.citation: J Exp Bot. 2002 Apr;53(370):927-37
references.pmid: 11912235
references.citation: ScientificWorldJournal. 2001 Nov 06;1 Suppl 2:61-9
references.pmid: 12805782
references.citation: J Biol Chem. 1992 Aug 5;267(22):15432-9
references.pmid: 1322398
references.citation: Nat Rev Genet. 2003 Dec;4(12):948-58
references.pmid: 14631355
references.citation: Trends Plant Sci. 2004 Dec;9(12):597-605
references.pmid: 15564127
references.citation: Planta. 2005 Jun;221(3):328-38
references.pmid: 15599760
references.citation: Ann Bot. 2005 Apr;95(5):853-61
references.pmid: 15701662
references.citation: Ann Bot. 2005 Jun;95(7):1187-98
references.pmid: 15802311
references.citation: Plant Physiol. 2006 Feb;140(2):444-56
references.pmid: 16407450
references.citation: Theor Appl Genet. 2006 Jun;113(1):33-8
references.pmid: 16614833
references.citation: Plant Physiol. 1992 Dec;100(4):1737-43
references.pmid: 16653191
references.citation: Biochem J. 1938 Oct;32(10):1877-89
references.pmid: 16746822
references.citation: Plant Cell. 2006 Oct;18(10):2767-81
references.pmid: 17041150
references.citation: Plant Cell Environ. 2006 Mar;29(3):315-30
references.pmid: 17080588
references.citation: Plant Physiol. 2007 Jan;143(1):530-9
references.pmid: 17114271
references.citation: Plant Cell. 2006 Nov;18(11):3252-74
references.pmid: 17138698
references.citation: J Exp Bot. 2008;59(7):1615-24
references.pmid: 17975207
references.citation: Plant Cell Physiol. 2008 May;49(5):843-52
references.pmid: 18420596
references.citation: Plant Biol (Stuttg). 2008 Sep;10 Suppl 1:15-22
references.pmid: 18721308
references.citation: Proteomics. 2009 Jul;9(13):3580-608
references.pmid: 19609964
references.citation: Ann Bot. 2010 Jun;105(7):1141-57
references.pmid: 20299346
references.citation: J Exp Bot. 2010 Oct;61(15):4313-24
references.pmid: 20693411
references.citation: Physiol Plant. 2012 May;145(1):203-14
references.pmid: 22121866
references.citation: Physiol Plant. 2012 May;145(1):130-9
references.pmid: 22242903
references.citation: Plant Cell Environ. 2013 Feb;36(2):328-42
references.pmid: 22789031
references.citation: Science. 2012 Nov 2;338(6107):655-9
references.pmid: 23118188
references.citation: Methods Mol Biol. 2014;1090:335-46
references.pmid: 24222425
references.citation: PLoS One. 2014 Jan 29;9(1):e87689
references.pmid: 24489951
references.citation: J Exp Bot. 2014 Jul;65(14):3927-47
references.pmid: 24567494
references.citation: J Exp Bot. 2014 Jul;65(14):3813-24
references.pmid: 24790115
references.citation: J Exp Bot. 2015 May;66(9):2461-73
references.pmid: 25792758
references.citation: Oecologia. 1989 Jan;78(1):9-19
references.pmid: 28311896
references.citation: Arch Biochem Biophys. 1973 Nov;159(1):113-22
references.pmid: 4150338
references.citation: Nature. 1970 Aug 15;227(5259):680-5
references.pmid: 5432063
references.citation: Plant Mol Biol. 1996 Oct;32(1-2):275-302
references.pmid: 8980483
references.citation: Plant Mol Biol. 1997 Mar;33(5):821-34
references.pmid: 9106506
references.citation: Plant Physiol. 1997 Apr;113(4):1329-41
references.pmid: 9112779
references.citation: Anal Biochem. 1976 May 7;72:248-54
references.pmid: 942051