Expression of maize gamma-zein and beta-zein genes in transgenic Nicotiana tabacum and Lotus corniculatus

Accumulation of zeins, the endosperm storage proteins of maize, in a heterologous plant expression system was attempted. Plants of Nicotiana tabacum and Lotus corniculatus were transformed by Agrobacterium with binary vectors harbouring genes that code for gamma-zein and beta-zein, two zeins rich in sulphur amino acids. Adding the ER retention signal KDEL to the C-terminal domainmodified the zein polypeptides. Significant levels of gamma-zein:KDEL and beta-zein:KDEL were detected in primary transformants of tobacco. Moreover, the two zeins colocalized in leaf protein bodies of gamma-/beta-zein:KDEL plants derived from a cross between two primary transformants. Coexpression of gamma-zein:KDEL and beta-zein:KDEL could be a useful strategy to obtain genotypes of forage legumes which are able to accumulate sulphur amino acids to high levels. As a first step, L. corniculatus plants expressing gamma-zein:KDEL in the leaves were obtained.