Dubousset L, Abdallah M, Desfeux A S, Etienne P, Meuriot F, Hawkesford M J, Gombert J, Ségura R, Bataillé M-P, Rezé S, Bonnefoy J, Ameline A F, Ourry A, Le Dily F, Avice J C
INRA, UMR INRA-UCBN 950 Ecophysiologie Végétale, Agronomie et Nutritions NCS, Esplanade de la Paix, F-14032, Caen, France.
J Exp Bot. 2009;60(11):3239-53. doi: 10.1093/jxb/erp172. Epub 2009 Jun 24.
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.
利用长期（³⁴）SO₄²⁻标记方法，结合叶片衰老进程研究（使用SAG12/Cab作为分子指标）以及参与液泡硫酸盐外流的转运蛋白BnSultr4;1和BnSultr4;2的基因表达，研究了硫限制对油菜莲座期内源性硫化合物再动员的影响，以及这些过程中与氮有效性的相互作用。在0.3 mM（³⁴）SO₄²⁻（过量1原子%）的水培条件下培养51天后，停止标记，将植株置于高硫 - 高氮（HS - HN，对照）、低硫 - 高氮（LS - HN）或低硫 - 低氮（LS - LN）条件下28天。与对照相比，LS - HN植株叶片衰老延迟，虽然地上部生长和叶片可溶性蛋白含量未受影响，但老叶中的硫、（³⁴）硫和SO₄²⁻含量迅速下降，并与BnSultr4;1的上调相关。在LS - LN植株中，地上部生长减少，叶片衰老加速，老叶中硫的快速再动员伴随着（³⁴）硫和SO₄²⁻的减少、更高的蛋白质再动员以及BnSultr4;2的上调，但BnSultr4;1的表达没有任何变化。数据表明，为了在硫限制下维持生长对硫的需求，（i）在LS - HN条件下液泡SO₄²⁻被特异性再动员，且叶片衰老没有加速，（ii）SO₄²⁻的再动员与BnSultr4;1和/或BnSultr4;2表达的上调有关，（iii）硫酸盐再动员与BnSultr4基因表达上调之间的关系具体取决于氮的有效性。
