Differential seed maturation uncouples fertilization and siring success in Oenothera organensis (Onagraceae)

Abstract

This study examines ovule fertilization and seed maturation success in an evening primrose, Oenothera organensis, using transgenic plants. The reproductive success of several pollen donors was compared using individuals transformed with the GUS (/3-glucuronidase) marker gene which allowed the genotype of developing ovules to be determined prior to seed abortion. This marker gene allowed us to discriminate between a pollen donor's success in fertilizing ovules and its success in siring seeds. Transformed plants had decreased microgametophytic vigour, as evidenced by lower than expected fertilization success in vivo and slower pollen tube growth rates in vitro. However, transformation had no apparent effect on offspring sporophytic vigour, including seed mass, seedling emergence and dry weight. This illustrates the effectiveness of fertilization competition in screening out poorly functioning haploid genomes as suggested by Mulcahy (1979). We found significant differences between the percentage of ovules fertilized and the percentage of seeds sired by a pollen donor in four of eight cases. Hence, fertilization success does not always predict seed paternity. The proportion of seeds sired by the transformed donor with very low fertilization success increased, whereas the proportion sired by the donor with relatively high fertilization success was reduced. This resulted in nearly equal siring ability for the two donors in spite of their difference in fertilization ability.

The effects of pollen load size and donor diversity on pollen performance, selective abortion, and progeny vigor in Mirabilis jalapa (Nyctaginaceae)

“…Also, observed differences in gametophyte performance might be masked in the diploid state, thereby obscuring expected fitness differences. This was observed by Havens and Delph (1996) who found that a transformation that affected gametophyte vigor did not affect sporophyte vigor.…”

Seed paternity in flowering plants: an evolutionary perspective

“…Because of this, the maternal environment may have a strong influence on embryo development and survival (including seed abortion, e.g. Havens & Delph 1996), and as a result it may be difficult to attribute the events occurring between pollen deposition and fruit maturation unambiguously to paternal or maternal influences, to sporophytic or gametophytic traits.…”

Pollination efficiencies of flower‐visiting insects as determined by direct genetic analysis of pollen origin

“…Color polymorphism of pollen grains ( Jorgensen et al, 2006 ) can be readily assessed, but the discrimination is relatively poor and adaptation is restricted to specifi c species. Although gene transformation ( Havens and Delph, 1996 ;Hudson et al, 2001 ) and differences in ploidy ( Williams et al, 1999 ) can also distinguish pollen genotypes in vivo, these methods are unsuitable for processing the large numbers of samples required for analysis of natural populations.…”