Zein accumulation in forage species (Lotus corniculatus and Medicago sativa) and coexpression of gamma-zein:KDEL and beta-zein:KDEL polypeptides in tobacco leaf

Plants of birdsfoot trefoil (Lotus corniculatus), alfalfa (Medicago sativa) and tobacco (Nicotiana tabacum) were transformed by Agrobacterium with binary vectors harbouring genes that code either for wild-type and gamma-zein:KDEL, or for beta-zein:KDEL. The maize seed storage proteins gamma-zein and beta-zein are rich in sulphur amino acids and our long-term goal was to improve alfalfa and birdsfoot trefoil forage quality. Significant levels of zeins were detected in leaves of birdsfoot trefoil transformants, ranging up to 0.055% and to 0.30% of total extractable protein for gamma-zein and beta-zein:KDEL, respectively. In leaves of alfalfa, gamma-zein:KDEL expression level was up to 0.026% of the total extractable protein. From a F1 population of transgenic tobacco a plant was selected in which the amount of zeins (gamma-zein:KDEL plus beta- zein:KDEL) accounted for 1.1% of total extractable protein.