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5 Abstract Tobacco mature pollen rehydrates in vivo on a stigma tissue, and develops into the rapidly-growing pollen tube. This rehydration process is accompanied by the de-repression of stored mRNA transcripts, resulting in the synthesis of novel proteins. Furthermore, such metabolic switch is also likely to be regulated on the level of post-translational modifications of the already-present proteins, namely via phosphorylation, since it was shown to play a significant regulatory role in numerous cellular processes. Since only a minor part of proteins is phosphorylated in a cell at a time, the employment of various enrichment techniques is usually of key importance. In this diploma project, metal oxide/hydroxide affinity chromatography (MOAC) with aluminium hydroxide matrix was applied in order to enrich phosphoproteins from the mature pollen and the 30-minute in vitro activated pollen crude protein extracts. The enriched fraction was separated by both 2D-GE and gel-free liquid chromatography (LC) approaches with subsequent mass spectrometric analyses. Collectively, 139 phosphoprotein candidates were identified. Additionally, to broaden the number of phosphorylation sites identified, titanium dioxide phosphopeptide enrichment of trypsin-digested mature pollen crude extract was performed. Thanks to the...