An endosperm-specific promoter for stable trans-gene expression in barley grain

The bi-functional alpha amylase subtilisin inhibitor (ASI), an endogenous inhibitor synthesised in the barley grain, inhibits high pI-group of alpha-amylases and the bacterial protein subtilisin. The expression of the asi gene in developing barley grain is thought to be under control of the hormones abscisic acid (ABA) and giberellic acid (GA), a control which is antagonistic to that of alpha-amylase. Such controlled expression of ASI and alpha-amylase ensures that starch is either accumulated during grain filling or is digested during seed germination. The levels of ASI as compared to total seed proteins remain relatively stable in response to various climatic conditions. This suggests that the promoter and possibly the 3`-untranslated region of the asi could be used to control stable expression of trans-genes in the barley grain and possibly other cereals. The promoter and the 3'-untranslated region of asi have been isolated and a number of putative DNA-elements, which are known to regulate expression of other genes in endosperm tissue, have been identified. Functional analysis of progressive 5'-deletions of the asi-promoter fused to the green fluorescent protein gene (gfp) will be studied to identify regions controlling hormonal regulation and endosperm specific expression. The 3'-untranslated region of asi will also be studied to determine it's role in hormonal control or message stability.