A combined 15N tracing/proteomics study in Brassica napus reveals the chronology of proteomics events associated with N remobilisation during leaf senescence induced by nitrate limitation or starvation.
Our goal was to identify the leaf proteomic changes which appeared during N remobilisation that were associated or not associated with senescence of oilseed rape in response to contrasting nitrate availability. Remobilisation of N and leaf senescence status were followed using (15)N tracing, patterns of chlorophyll level, total protein content and a molecular indicator based on expression of senescence-associated gene 12/Cab genes. Three phases associated with N remobilisation were distinguished. Proteomics revealed that 55 proteins involved in metabolism, energy, detoxification, stress response, proteolysis and protein folding, were significantly induced during N remobilisation. Four proteases were specifically identified. FtsH, a chloroplastic protease, was induced transiently during the early stages of N remobilisation. Considering the dynamics of N remobilisation, chlorophyll and protein content, the pattern of FtsH expression indicated that this protease could be involved in the degradation of chloroplastic proteins. Aspartic protease increased at the beginning of senescence and was maintained at a high level, implicating this protease in proteolysis during the course of leaf senescence. Two proteases, proteasome beta subunit A1 and senescence-associated gene 12, were induced and continued to increase during the later phase of senescence, suggesting that these proteases are more specifically involved in the proteolysis processes occurring at the final stages of leaf senescence.
Desclos
Marie
M
INRA, UMR INRA/UCBN 950 Ecophysiologie Végétale, Agronomie et nutritions N C S, IFR 146 ICORE, Institut de Biologie Fondamentale et Appliquée, Université de CAEN Basse-Normandie, Caen, France.
Etienne
Philippe
P
Coquet
Laurent
L
Jouenne
Thierry
T
Bonnefoy
Josette
J
Segura
Raphaël
R
Reze
Sandrine
S
Ourry
Alain
A
Avice
Jean-Christophe
JC
D018533:Biomass; D029688:Brassica napus / Q000737:chemistry / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D009566:Nitrates / Q000494:pharmacology*; D018515:Plant Leaves / Q000737:chemistry / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D040901:Proteomics; D011849:Radioactive Tracers
D009566:Nitrates; D010940:Plant Proteins; D011849:Radioactive Tracers; D002734:Chlorophyll