Study On Calcium Signaling During Embryo Development/Abortion In Peanut (Arachis Hypogaea L.)

The embryo abortion of peanut (Arachis hypogaea L.) growing on drought sandy soil occurs usually due to calcium shortage in the soil in South China. An attempt was made to improve our understanding on the dynamic changes of calcium signaling, including calcium ion and calmodulin (CaM) during embryo development/abortion of peanut plants. The distribution of membrane-bound calcium and calmodulin in the young embryo was observed by fluorescence microscope with chlorotetracycline (CTC) and fluphenanize (FPZ) fluorescence probe. Localization of calcium and calmodulin were examined ultracytochemically with potassium pyroantimonate and colloid gold respectively. Contents of calmodulin of different periods of embryo development or abortion were measured by enzyme-linked immunosorbent assay (ELISA).The results are summarized as following:1. Embryo abortion of peanut seemed to be attributed to some obstructions in accumulating of proteins and lipids.2. Membrane-bound calcium was distributed uniformly while more calmodulin was deposited in the growing actively areas. And there was no difference between embryos grown in the soils containing high and low calcium until 9 days after fruit needle buried.3. Observation by electron microscope showed that distribution of calcium ion was not the quite same all the periods. Embryo absorbed lots of calcium 6 days after fruit needle buried, and most of calcium concentrated in cytoplasm in earlier stage and a little in vacuole. Subsequently calcium also could be found in intercellular cleft, and calcium lay along the cell membrane in the cytoplasm after cell enriched. But most of calcium ion concentrated in vacuole if the pods were grown in low calcium soil.4. Ultracytochemical localization of calmodulin by colloid gold revealed that distribution of calmodulin was not uniform; there was much calmodulin where proteins accumulated. If the pods were grown in low calcium soil, lots of calmodulin distributed out of the cell.5. Using enzyme-linked immunosorbent assay (ELISA), contents of calmodulin in embryo of 6 days after fruit needle buried were found decreasing abruptly, and then recovering rapidly.Based on the above, calmodulin could not be activated, distribution and contents of calcium and calmodulin underwent change due to calcium shortage which may also inhibited accumulation of proteins and lipids. so that the embryo aborted.