Developmental changes of protein, proline and some antioxidant enzymes activities in somatic and zygotic embryos of Persian walnut (Juglans regia L.)

In a comparative study, total protein, proline content, total protein spectra (SDS-PAGE) and activities of some antioxidant enzymes including peroxidase (POX), catalase (CAT), superoxide dismutase (SOD) and polyphenol oxidase (PPO) of somatic and zygotic embryos of Persian walnut cultivar 'Chandler' at different developmental stages were analyzed. Moreover, opaque white cotyledonary somatic embryos as normal mature embryos and translucent ones as abnormal mature embryos were compared histologically, too. Accumulation of proteins was observed during zygotic embryos maturation but in somatic embryos, proteins accumulated in torpedo shaped embryos. Among all the protein bands were present in somatic embryos, two 20 and 11.7 kDa proteins were appeared only in opaque white cotyledonary stage embryos and were absent in early developmental stages and in translucent cotyledonary embryos. Presumably they could be considered as markers for normal maturation of somatic embryos of Persian walnut. Proteins with 49, 37, 35 and 20 kDa were present in both somatic and zygotic embryos. Some typical protein bands with considerable changes during the development were identified in zygotic embryos. The results showed that CAT, POX, PPO and SOD not only could be considered as markers for developmental stages of somatic embryos both quantitatively and qualitatively but also could reflect the differences between in vivo and in vitro condition. Proline content showed interesting changes during maturation of both somatic and zygotic embryos. Translucent cotyledonary embryos showed lack of starch grains in epidermal cells in contrast to opaque ones, but in total protein and proline content they were similar. Torpedo shaped somatic embryos showed the highest level of proline, protein and antioxidant enzymes activities.