Transient expression of β-glucuronidase in different cellular compartments following biolistic delivery of foreign DNA into wheat leaves and calli.

Transient expression of β-glucuronidase (GUS) in different cellular compartments following biolistic delivery of chloroplast or nuclear expression vectors into wheat leaves or calli, derived from anther culture or immature embryos, is reported here. When pB1121, the nuclear GUS vector, was used to bombard wheat cells, the β-glucuronidase product, an insoluble indigo dye, was observed evenly throughout the cytosol. But, when the chloroplast expression vector pHD203-GUS was used for bombardments, the indigo dye (GUS product) was subcellularly localized within the chloroplasts of wheat cells. The observation of GUS expression in albino plastids, when anther culture derived albino leaves were bombarded with the chloroplast expression vector pHD203-GUS, suggests the presence of a functional protein synthetic machinery in these organelles. GUS expression was also observed in regenerable calli derived from wheat immature embryos bombarded with pHD203-GUS. Leaves or calli bombarded with pUC19, as negative controls, did not show any GUS expression. These results constitute the first demonstration of foreign gene expression in chloroplasts of a monocot and that a dicot chloroplast promoter functions in a monocot chloroplast.