The promoter of barley trypsin-inhibitor BTI-CMe, discriminates between wheat and barley endosperm protoplasts in transient expression assays.

Several promoter fragments from the barley gene coding for trypsin inhibitor, BTI-CMe, have been fused to the β-glucuronidase (GUS) reporter gene and these chimeric constructs used for transient expression in protoplasts. Transfection of developing endosperm protoplasts from barley (cv Bomi) show a maximum GUS expression of about 50% of that driven by the cauliflower mosaic virus 35S promoter, while in wheat endosperm protoplasts expression is less than 10%. No significant expression is found in transfected leaf protoplasts from barley, wheat or tobacco (<2% of the 35S control). All the information required for endosperm and barley specificity is present in the 343 bp proximal to the translation initiation site.