One of the remarkable features about the reproductive biology of pines is the prolonged growth of pollen tubes. Pine pollen grains germinate on the nucellus and produce a tube that ceases growth while not even halfway through. Pine pollen tubes remain dormant in the nucellus for more than a year. To advance our understanding on how pollen germination and tube growth are regulated in conifers, this study aims to characterize the proteins which are differentially expressed during the initial stages of pollen tube growth. Proteins were extracted from several stages including mature ungerminated pollen (unhydrated and hydrated) and pollen tubes (1- and 2-day old). Proteins were separated by 1- and 2-dimensional gel electrophoresis. Some proteins were found to be expressed in response to hydration (27- and 33-kDa), others were expressed only in pollen tubes (26-kDa) or upregulated in pollen tubes (31-kDa). One of the first steps in the characterization of a newly purified protein is the determination of its amino acid sequence. For a rapid survey screening and characterization of protein samples, investigation of their tryptic digests by LC/MS/MS (HPLC coupled with tandem Mass Spectrometry). The resulting molecular weights of a few peptides of a protein can be used for its identification by database search. Initial results indicate that one of the differentially expressed proteins coincide with a reductase enzyme that is involved in the biosynthesis of compounds that play a defensive role in plants.

Key words: conifer, differential expression, pine, pollen tubes, proteins, proteomics