Differential display proteomic analysis of Picea meyeri pollen germination and pollen-tube growth after inhibition of actin polymerization by latrunculin B

To investigate roles of the actin cytoskeleton in growth of the pollen tube of Picea meyeri, we used the actin polymerization inhibitor latrunculin B (LATB) under quantitatively controlled conditions. At low concentrations, LATB inhibited polymerization of the actin cytoskeleton in the growing pollen tube, which rapidly inhibited tip growth. The proteomic approach was used to analyse protein expression-profile changes during pollen germination and subsequent pollen-tube development with disturbed organization of the actin cytoskeleton. Two-dimensional electrophoresis and staining with Coomassie Brilliant Blue revealed nearly 600 protein spots. A total of 84 of these were differentially displayed at different hours with varying doses of LATB, and 53 upregulated or downregulated proteins were identified by mass spectrometry. These proteins were grouped into distinct functional categories including signalling, actin cytoskeleton organization, cell expansion and carbohydrate metabolism. Moreover, actin disruption affected the morphology of Golgi stacks, mitochondria and amyloplasts, along with a differential expression of proteins involved in their functions. These findings provide new insights into the multifaceted mechanism of actin cytoskeleton functions and its interaction with signalling, cell-expansion machinery and energy-providing pathways.