Proteomics Analysis Of Spore Germination From Osmunda Cinnamomea L.var. Asiatica

Osmunda cinnamomea L. var. asiatica is an herbaceous plant species in the genus Osmunda in Osmundaceae, which is a famous potherb with medicinal value. It is also a good model for investigating the mechanism of spore germination.We analyzed the cytological features during the five stages (mature spores, rehydratd spores, double cell spores, germinating spores and spores with prothallus cell) of the O. cinnamomea spore germination. The results showed that mature spores had trilete and its nucleus located in the middle of the cell. After dark treatment for 12h, the spores had completed rehydration to become rehydrated spores. The nucleus of the rehydrated spores largened and migrated towards a side. Some of the rehydrated spores nucleus had been copied, but not separated. After continuous illumination for 23h, spores devided to a smaller cell and a larger cell, which was named double-cell spores. The nucleus of the larger cell was surrounded by a large number of plasmids containing one or more starch grains, and the number of the vacuoles in the large cell was significantly more than that in the rehydrated spores. The smaller cell started the polar growth at the opening of the trilete. After 37h of continuous illumination, spore started germation. The spore wall split entirely, and the smaller cell begain top-growth by elongating a rhizoid. The vacuole volume of the larger cell was significantly larger, and the plasmids around the nucleus change to shuttle-like shape. Under light for 57h, the large cell divided again to form protonema primitive cells and at this time the rhizoid length of the majority spores equal to or slightly longer than the diameter of the spore.Importantly, we identified 101 differentially expressed proteins during these five stages of the spore germination using proteomics technology. These proteins were involved in photosynthesis (36%), energy metabolism (6%), metabolic (20%), stress and defense (6%), protein synthesis (4%), protein folding and degradation (16%), membrane and transport (5%), cell structure (2%), and unknown function (4%). Differentially-expressed protein spots were divided into five expression patterns, and the protein expression abundance of each pattern reached the highest value in mature spores, rehydration spores, double cell spores, germinating spores and spores with prothallus respectively. The expression abundance of proteins involved in photosynthesis, metabolism, and protein folding and degradation changed significantly.in all the differentially expressed proteins at different stages. These results are provid a proteomics evidence for further analysis the molecular mechanisms of some key steps upon spore germination including the establishment of cell polarity, asymmetric division and rhizoid top growth.