Proteome Analysis Of Signaling To The Actin Cytoskeleton In Picea Meyeri Pollen Tube

Pollen tube as a carrier to deliver the sperm to the ovule during the process of sexual plant reproduction in higher plants. Pollen tube growth is highly polarized and actin cytoskeleton dependent, moreover pollen tube has become a relatively well-characterized model system in which to study cell-cell recognition, intra-and intercellular signaling in higher plants. To investigate roles of the actin cytoskeleton in the growth of pollen tube of Picea meyeri Rehd. et Wils., we used actin polymerization inhibitor latrunculin B (LATB) under quantitatively controlled conditions to perturb the actin cytoskeleton and observation with laser scanning confocal microscope. At low concentrations, LATB depolymerized actin cytoskeleton in the growing pollen tube and this rapidly inhibited their tip growth. Proteomic approach was used to analyse protein expression profile changes during the pollen tube development with disturbed organization of the actin cytoskeleton. Two-dimensional electrophoresis displayed nearly 500 Coomassie Brilliant Blue-stained protein spots. A total of 110 protein spots were reproducibly differentially displayed after 28 hours of LATB treatment, and 35 differentially displayed proteins were identified by mass spectrometry. Among the identified proteins, in case of 18 protein spots are upregulated upon to LATB treatment while 17 spots are downregulated. These proteins were grouped into distinct functional categories including proteins involved in carbohydrate metabolism, stress-response, signaling and cell expansion. Some of them are relevant for the energy metabolism in the cell which is linked to the signal-dependent actin re-organization. In addition, two proteins (reversibly glycosylated polypeptide-1 and type IIIa membrane protein cp-wap13) identified in this study decreased significantly and almost disappeared when the concentration of LATB increased to 50 nM. These two proteins function in cell wall polysaccharide biosynthesis, which indicate that the actin disruption interferes with secretory system and deposition of cell wall components. Finally, the down regulation of actin further revealed that the actin cytoskeleton may function in pollen tube growth by providing, or supporting, a mechanism that regulates a signal mediated elongation to allow the pollen tube to attain its final destination in particular time during transport of sperm cells.