Minisymposium 26: Proteomics

Abs # 47001: Characterization of Differentially Expressed Pollen Tube Proteins: Towards Our Understanding of the Mechanism of Pollen Tube Development in Pines

Presenter:	Fernando, Danilo D, fernando@esf.edu
Authors	Fernando, Danilo D (A)
Affiliations:	(A): Faculty of Environmental and Forest Biology, State University of New York, College of Environmental Science and Forestry
Web Site:	http://www.esf.edu/efb/fernando

Conifer pollen tubes are very different from those of flowering plants because of their slow rate and extended period of growth, extremely delayed gametogenesis, and distinct cytoskeletal control. These differences are not subtle but represent major evolutionary divergence in male reproductive development and indicate that a different mechanism of pollen tube growth and development occurs in conifers. Proteins that are differentially expressed in pollen tubes may play a significant role in pollen tube development. To reveal the identity of these proteins, comparative two-dimensional (2D) gel electrophoresis was done using Eastern white pine (Pinus strobus) proteins extracted from dry, ungerminated pollen grains and 2-day old pollen tubes. Duplicate silver-stained 2D gels from both samples were scanned and analyzed. The results show that 645 and 652 protein spots in the pI range of 4.6 to 7.9 and Mr range of 14 to 172 kDa were clearly resolved from pollen grains and pollen tubes, respectively. Thirty-six protein spots in pollen grains were not found in pollen tubes, while 43 protein spots in pollen tubes were not found in pollen grains. Protein spots with increased intensity (at least 5-fold) were 28 and 13 for pollen grains and pollen tubes, respectively. These results show that the 56 differentially expressed proteins in pine pollen tubes are different from those (64) in the pollen grains. To establish the identity of the differentially expressed pollen tube proteins, 28 protein spots were chosen and sequenced through Electrospray Ionization coupled with a Quadrupole Time-of-Flight Mass Spectrometry (ESI-Q-TOF-MS). The partial amino acid sequences generated were used to search various publicly available databases. Identification of all but 2 protein spots was successful based on similarity of sequences with previously characterized proteins from other species, but many of these are from conifers. In pollen tubes, most of the differentially expressed proteins are involved in metabolism (e.g., aldolase, dehydrogenase and enolase), signaling (e.g., calmodulin, calreticulin, and chaperonin), and defense response (e.g., reductase and peroxidase). The temporal and spatial expression patterns of some of these proteins are currently being investigated. This study shows that pollen tube development involves the expression of a unique set of proteins different from those expressed in the mature ungerminated pollen.