ANALYSIS OF GENE-REGULATION IN GROWING POLLEN TUBES OF ANGIOSPERM ANDGYMNOSPERM SPECIES USING MICROPROJECTILE BOMBARDMENT

A microprojectile based transient expression assay was used to investi gate the functional conservation of gene regulatory mechanisms in the male gametophytes of an angiosperm (Nicotiana tabacum) and two gymnosp ermous (Picea abies and Pinus pinaster) species. The activities of two angiosperm gene promoters, which have previously shown to be either p referentially expressed in the male gametophyte (lat52) or highly expr essed in both the sporophyte and male gametophyte (Act1), were analyse d. The results showed that in P. abies and P. pinaster, activity of th e Act1 promoter was significantly higher than the activity of the lat5 2 promoter, while the converse was observed in N. tabacum. Detailed an alysis of lat52 5' promoter deletions demonstrated that although the m inimal -67 bp lat52 core promoter was active at low levels in all thre e species, upstream regulatory elements conserved among several pollen -expressed genes, including the PBI element, were not functional in P. abies and P. pinaster. These results suggest that both taxa-specific and conserved regulatory mechanisms operate to control gene expression during pollen germination and tube growth.