title: Species preferentiality of the pollen tube attractant derived from the synergid cell of Torenia fournieri.
abstract: The synergid cell of Torenia fournieri attracts pollen tubes by a diffusible but yet unknown chemical attractant. Here we investigated the species difference of the attractant using five closely related species in two genera, namely T. fournieri, Torenia baillonii, Torenia concolor, Lindernia (Vandellia) crustacea, and Lindernia micrantha. These five species have an exserted embryo sac, and ablation experiments confirmed that their synergid cells attracted the pollen tube. When ovules of T. fournieri and one of the other species were cultivated together with pollen tubes of each species, pollen tubes were significantly more attracted to synergid cells of the corresponding species. The attraction was not affected by the close proximity of embryo sacs of different species. This suggests that the attractant is a species-preferential molecule that is likely synthesized in the synergid cell. The calcium ion, long considered a potential attractant, could not serve as the sole attractant in these species, because elevation of the calcium ion concentration did not affect the observed attraction. In vivo crossing experiments also showed that the attraction of the pollen tube to the embryo sac was impaired when pollen tubes of different species arrived around the embryo sac, suggesting that the species preferentiality of the attractant may serve as a reproductive barrier in the final step of directional control of the pollen tube.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Tokyo 113-0033, Japan. higashi@biol.s.u-tokyo.ac.jp
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Higashiyama
authors.forename: Rie
authors.initials: R
authors.lastname: Inatsugi
authors.forename: Sachio
authors.initials: S
authors.lastname: Sakamoto
authors.forename: Narie
authors.initials: N
authors.lastname: Sasaki
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Mori
authors.forename: Haruko
authors.initials: H
authors.lastname: Kuroiwa
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakada
authors.forename: Hisayoshi
authors.initials: H
authors.lastname: Nozaki
authors.forename: Tsuneyoshi
authors.initials: T
authors.lastname: Kuroiwa
authors.forename: Akihiko
authors.initials: A
authors.lastname: Nakano
mesh_terms: D001685:Biological Factors / Q000737:chemistry / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D035264:Flowers / Q000166:cytology / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D053205:Pollen Tube / Q000502:physiology*; D028083:Scrophulariaceae / Q000166:cytology* / Q000235:genetics / Q000502:physiology*; D013045:Species Specificity; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D001685:Biological Factors; D005680:gamma-Aminobutyric Acid; D002118:Calcium