Abstract
Fertilization is a key process for plant sexual reproduction. After pollination and germination of pollen grains on the stigma, the pollen tube, which carries two male sperm cells, are guided by and growing toward the female ovule. This pollen tube guidance is highly species specific and is thought to be one of a mechanism to generate interspecies barrier. We have recently identified that a group of Defensin-like Cysteine-Rich Polypeptides, LUREs, are the pollen tube attractants secreted from the synergid cells of Torenia fournieri. Because sequence diversity is a general feature of Defensin-like proteins, we hypothesized that diversity of LUREs may contribute species-specific pollen tube attraction and speciation. To clarify their molecular features, we isolated LURE homologues from related species of T. fournieri. We found one LURE homologous gene that was not expressed in the ovule. Some key amino acids were substituted in its product, suggesting that this gene might be a pseudo-gene in the species. We also found several LURE homologues expressed predominantly in the ovule. We are currently purifying these LURE proteins and testing their activities for pollen tube attraction.
