Tools for seed-specific expression leading to improved quality and defence of cereals

Abstract

Genomes of cereals are one of the many that humans have remodelled through careful selection and breeding, where breeding criteria such as high yield, disease tolerance or environmental adaptability dictated the modification. Biotechnology offers another avenue for modification of genomes by transferring one or more transgenes and also controlling their expression. We are interested in using promoter elements as tools to control transgene expression to improve quality and or defence. We have analysed the promoter of the bifunctional alpha-amylase subtilisin inhibitor gene (Isa) in transgenic barley and rice. A number of other seed-specific promoters were also used in this study. Or results suggest that seed-specific promoters from wheat and barley and rice directed expression of reporter gene in seeds of transgenic plants of the corresponding species and also between species. However, seed-specific expression of reporter gene in transgenic rice plants was not maintained under control of seed-specific promoters from wheat and barley. A bi-factorial cis-element termed the endosperm box is one of a number of cis-acting elements that have been implicated to be responsible for seed-specific/endospermspecific expression. The endosperm-box is comprised of two elements namely the E-motif and the GCN4 motif. The promoters from barley and wheat that we investigated in transgenic plants have the E-motif or the GCN4 motif or combinations of both. In rice, endosperm-specific expression is not contributed by the endosperm box but by other cis-elements namely the AACA motif and the GCN4 motif. Analysis of transgenic seeds is ongoing and data reflecting promoter strength will be discussed. Implications of the Isa promoter in cereals breeding for improved quality and defense will be discussed