Differential specificity of cereal promoters in homologous and heterologous cereals

Improving the cereal grain using a transgenic approach would require the use of specific gene/s but also the use of specific promoter elements to control the spatial and temporal expression of the gene/s. We have studied several seed-specific cereal promoters to investigate if promoter strength and specificity is maintained from a homologous to a heterologous system. Transgenic rice, wheat and barley were generated to study promoters of the bifunctional alpha-amylase subtilisin inhibitor gene (Isa) form barley, the Em gene from wheat and a number of storage protein promoters from barley, rice and wheat. The isa promoter from barley show differential control of reporter gene expression in grains of transgenic wheat and rice. The wheat Em promoter shows comparable reporter gene expression in transgenic wheat, barley and rice. The seed-specific promoters from wheat, barley and rice directed seed-specific reporter gene expression in a homologous system. However, in a heterologous system the storage protein promoters either maintained seed-specific reporter gene expression, or showed differential control of reporter gene expression, or failed to direct any reporter gene expression. Analysis of transgenic rice and barley seeds is ongoing and data reflecting promoter strength will be discussed. Possible reasons for this differential control of reporter gene expression between homologous and heterologous systems, and implications for using cereal promoters across other cereal species for transgenic breeding will be discussed.