Abstract: Abstract: 【Objective】To investigate the temporal and spatial expression pattern of calmodulin mRNA in pear ovaries and fruitlets, this study aimed to elucidate the mechanism of how fertilization promotes calcium uptake, increase calmodulin content and interaction between them.【Method】The ovaries and fruitlets before and after flowering of ten-year-old ‘Huanghua’ pear(Pyrus pyrifolia NaKai) were investigated, via northern hybridization and mRNA in situ hybridization for the expression level and localization of calmodulin gene .【Result】Results demonstrated that the expression level of calmodulin gene increased gradually before flowering, reached the peak at full blossom, and then decreased after flowering. mRNA in situ hybridization showed that calmodulin mRNA located on the epidermis, sarcocarp, ovule and flesh vascular bundles，while there was no expression at core and endocarp. The expression levels of calmodulin mRNA were as follows from high to low :epidermis , sarcocarp and endocarp; nucellus, embryonic sac and integument. At cellular level, calmodulin mRNA located at nucleolus, interstitial space and intercellular layer. With fruit developing, the expression level in different tissues showed that the highest level was at full blossom, and the expression level was slightly higher before blossom than that after blossom.【Conclusion】As showed that calmodulin mRNA expressed highly in flesh and ovule at blossom, and promoted calcium uptake.

Key words: Calmodulin mRNA, in situ hybridization, ovary/fruitlet