Changes in protein composition and protein phosphorylation during somatic embryogenesis and plant regeneration in peanut (Arachis hypogaea L.)

Changes in protein profiles and protein phosphorylation were studied in various stages of germinating somatic and zygotic embryos. Many proteins, which were expressed in cotyledonary stage somatic embryos, were also present in the zygotic embryos obtained from mature dry seed. The intensity of 22 kDa protein was much higher in zygotic embryos in comparison to cotyledonary somatic embryos. Proteins of 55, 53, 27 and 25 kDa did not vary in expression during different stages of germination of somatic and zygotic embryos. There was rapid accumulation of 28 kda protein in germinating zygotic and somatic embryos at 3 super(rd) stage and persisted during the subsequent stages of germination indicating the emergence of radical and plumule. A clear difference was observed in the patterns of protein phosphorylation in germinating somatic and zygotic embryos. A 50 kDa protein was heavily phosphorylated in mature zygotic embryos at 2 super(nd) stage of germination and disappeared in 3 super(rd) stage of germination. Protiens of 50 and 43 kDa proteins showed enhanced phosphorylation up to 3 super(rd) stage and drastic reduction was observed at 4 super(th) stage. In addition, phosphorylation of 68 and 65 kDa specifically appeared in 3 super(rd)stage of germinating somatic embryos and were not observed during any germinating stages of zygotic embryos.