Analysis of gene regulation in growing pollen tubes of angiosperm and gymnosperm species using microprojectile bombardment

Abstract

A microprojectile based transient expression assay was used to investigate the func tional conservation of gene regulatory mechanisms in the male gametophytes of an angiosperm (.Nicotiana tabacum) and two gymnospermous (Picea abies and Pinus pinaster) species. The activities of two angiosperm gene promoters, which have previously shown to be either preferentially expressed in the male gametophyte (lat52) or highly expressed in both the sporophyte and male gametophyte (A ct\), were analysed. The results showed that in P. abies and P. : pinaster, activity of the Actl promoter was significantly higher than the activity of the lat52 promoter, while the converse was observed in N. tabacum. Detailed analysis of Iat52 5' promoter deletions demonstrated that although the minimal -67 bp lat52 core promoter was active at low levels in all three 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 Lo control gene expression during pollen germination and tube growth.

Growth and development of conifer pollen tubes

“…The CaMV 35S and rice actin promoters showed intermediate expression levels. Martinussen et al (1995) analyzed the activities of two promoters that have been previously shown to be either preferentially expressed in the mature male gametophyte (LAT52) or highly expressed in both the sporophyte and male gametophyte (Act1). They showed that in growing pollen tubes of Picea abies and Pinus pinaster, the activity of the Act1 promoter was significantly higher than that of the LAT52 promoter.…”

Genetic Transformation of Plants

“…Several reports describe transient expression of reporter genes in various gymnosperm species (Hay et al 1994;Li et al 1994), ineluding Norway spruce (Martinussen et al 1994(Martinussen et al , 1995Häggman et al 1997). Regeneration of transgenie plants by applying transformed pollen in conventional pollination has, however, been less common.…”