Effect of sulphate deficiency on the plasma membrane polypeptide composition of Brassica napus

Highly purified oilseed rape (Brassica napus) root plasma membrane fractions were prepared and their polypeptide patterns analysed by two-dimensional gel electrophoresis. Sulphur starvation enhances the sulphate uptake capacity of B. napus roots. The relative abundance of several polypeptides increased significantly and specifically after sulphur starvation. Several of them (37, 38, 60, and 65 kDa), found in sulphur-starved plants, were more abundant in a phase-partitioned membrane fraction treated with Triton X-100/KBr, indicating that they are intrinsic polypeptides. One polypeptide (47 kDa) was identified in the in vitro translation products of the roots mRNAs as specific for S-starved plants. It was also present among the intrinsic polypeptides specific for —S plants. These plasma membrane polypeptides might be involved in sulphate uptake.