Remobilization of leaf S compounds and senescence in response to restricted sulphate supply during the vegetative stage of oilseed rape are affected by mineral N availability.
The impact of sulphur limitation on the remobilization of endogenous S compounds during the rosette stage of oilseed rape, and the interactions with N availability on these processes, were examined using a long-term (34)SO(4)(2-) labelling method combined with a study of leaf senescence progression (using SAG12/Cab as a molecular indicator) and gene expression of the transporters, BnSultr4;1 and BnSultr4;2, involved in vacuolar sulphate efflux. After 51 d on hydroponic culture at 0.3 mM (34)SO(4)(2-) (1 atom% excess), the labelling was stopped and plants were subject for 28 d to High S-High N (HS-HN, control), Low S-High N (LS-HN) or Low S-Low N (LS-LN) conditions. Compared with the control, LS-HN plants showed delayed leaf senescence and, whilst the shoot growth and the foliar soluble protein amounts were not affected, S, (34)S, and SO(4)(2-) amounts in the old leaves declined rapidly and were associated with the up-regulation of BnSultr4;1. In LS-LN plants, shoot growth was reduced, leaf senescence was accelerated, and the rapid S mobilization in old leaves was accompanied by decreased (34)S and SO(4)(2-), higher protein mobilization, and up-regulation of BnSultr4;2, but without any change of expression of BnSultr4;1. The data suggest that to sustain the S demand for growth under S restriction (i) vacuolar SO(4)(2-) is specifically remobilized in LS-HN conditions without any acceleration of leaf senescence, (ii) SO(4)(2-) mobilization is related to an up-regulation of BnSultr4;1 and/or BnSultr4;2 expression, and (iii) the relationship between sulphate mobilization and up-regulation of expression of BnSultr4 genes is specifically dependent on the N availability.
Dubousset
L
L
INRA, UMR INRA-UCBN 950 Ecophysiologie Végétale, Agronomie et Nutritions NCS, Esplanade de la Paix, F-14032, Caen, France.
Abdallah
M
M
Desfeux
A S
AS
Etienne
P
P
Meuriot
F
F
Hawkesford
M J
MJ
Gombert
J
J
Ségura
R
R
Bataillé
M-P
MP
Rezé
S
S
Bonnefoy
J
J
Ameline
A F
AF
Ourry
A
A
Le Dily
F
F
Avice
J C
JC
D000375:Aging; D001692:Biological Transport; D029741:Brassica rapa / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D013431:Sulfates / Q000378:metabolism; D013457:Sulfur Compounds / Q000378:metabolism*
D026901:Membrane Transport Proteins; D010940:Plant Proteins; D013431:Sulfates; D013457:Sulfur Compounds; D009584:Nitrogen