ACCUMULATION OF A SULFUR-RICH SEED ALBUMIN FROM SUNFLOWER IN THE LEAVES OF TRANSGENIC SUBTERRANEAN CLOVER (TRIFOLIUM-SUBTERRANEUM L)

A gene encoding a sulphur-rich, sunflower seed albumin (23% cysteine p lus methionine) was modified to contain the promoter for the 35S RNA o f cauliflower mosaic virus, in order to obtain leaf expression in tran sgenic plants. In addition, a sequence encoding an endoplasmic reticul um-retention signal was added to the 3' end of the coding region so as to stabilize the protein by diverting it away from the vacuole. The m odified gene was introduced into subterranean clover (T subterraneum L .) and its expression was detected by northern and western blots and b y immunogold localization. The albumin was accumulated in the lumen of the endoplasmic reticulum, and, among six independent, transformed li nes, it accumulated in the leaves of To transgenic plants at varying l evels up to 0.3% of the total extractable protein. The level of accumu lation of the sunflower albumin increased with increasing leaf age, an d in the older leaves of the most highly expressing plants of the T-1 generation it reached 1.3% of total extractable protein. Expression of the SSA gene was stable in the first and second generation progeny. T hese results indicate that there is potential for significantly improv ing the nutritional value of subterranean clover for ruminant animals such as sheep by expressing genes that code for sulphur-rich, rumen-st able proteins in leaves.