Changes in total soluble proteins and Ca2+ upon cryopreservation of Prunus mume pollen

Mei Flowers (Prunus mume) are traditional Chinese ornamental plants. Fifty-one Mei cultivars have been conserved in a pollen cryobank since 2003. We used two-dimensional electrophoresis (2-DE) of total soluble proteins and flow cytometric detection of Ca2+ fluorescence to probe changes in pollen grains before and after cryopreservation. Results indicated that: (1) electrophoresis maps of total soluble proteins before and after cryostorage of pollen from three cultivars were different, even though 70 percent of the protein spots among these three cultivars were matched after cryopreservation. We found some protein spots that changed in all three cultivars; their molecular weights and pI were between 12.6-72.8 kDa and 5.6-7.3, respectively; (2): the geometric mean of Ca2+ fluorescence intensity (GMFI) value of cryopreserved pollen was significantly higher compared with that of fresh pollen in cultivar 'Beijing Yudie'. GMFI increased during pollen germination in our studied cultivars, especially after 0.5 and 1.0 h of culturing. In addition, no positive correlation was found between pollen germination rate and GMFI in the present study.