Mature pollen from most plant species is metabolically quiescent; however, after pollination, it germinates quickly and gives rise to a pollen tube growing polarly to transport sperm into the embryo sac. The research in Prof. Tai Wang's group revealed that the most important difference between rice pollen and sporophytic tissues is preferential representation of wall-related proteins in the pollen proteome. During pollen germination, the wall-related proteins displayed two distinct changed patterns: up-regulated proteins mainly involve wall synthesis and wall hydrolysis/loosening enzymes, whereas those down-regulated were mainly involved in wall degradation and loosening. Thus, these results suggest that highly active wall dynamics is a prominent property of pollen function specialization ( Molecular & Cellular Proteomics, 2007 ).
Figure. Identification of differentially expressed proteins between pollen grains and polarly growing pollen tubes by two-dimensional gel