Pollination drop proteins and ovule transcripts of Cephalotaxus
Many gymnosperms produce an ovular secretion, the pollination drop, during reproduction. The drops serve as a landing site for pollen, but also contain a suite of ions and organic compounds, including proteins, that suggests diverse roles for the drop during pollination.
In the conifer Cephalotaxus koreana, Pirone-Davies et al. examine the proteome of the pollination drop and the transcriptome of the ovule. Identified proteins have putative functions of defence, polysaccharide metabolism, and pollen tube growth and guidance, but also novel functions such as starch and callose degradation. Transcriptome data provide insights into multiple metabolic processes that occur within the ovule and the drop just before fertilization including drop formation, ovule development, and conspecific pollen recognition. This is the first published ovule transcriptome of any gymnosperm.