Changes in the protein profile of Habanero pepper (Capsicum chinense J.) somatic embryos during development

Abstract

Protein profile was studied during the development of Capsicum chinense somatic embryos. The total protein content and profile of polypeptides (by sodium dodecyl sulfate polyacrylamide gel electrophoresis) of somatic embryos at different developmental stages (globular, heart-shaped, torpedo and cotyledonary stages) were analyzed. The protein profile of zygotic embryos included nine exclusive bands with molecular weights of 4.0, 5.2, 8.1, 13.7, 20.9, 23.7, 41, 50 and 69.3 kDa; these bands were not observed in the protein profile of somatic embryos. Coincidently, five of these bands possessed similar molecular weights to those reported for storage proteins in other plant species. Protein content showed a clear decreasing tendency with increasing somatic embryo development. The lowest protein content was detected in somatic embryos at the cotyledonary stage (0.436 µg/mg fresh weight), and the highest content was found in somatic embryos at the globular stage (2.98 µg/mg fresh weight). Total proteins two-dimensional electrophoresis (2-DE) analysis of mature zygotic embryo (prior to the desiccation) and cotyledonal somatic embryo, showed significant differences in the protein profile of both types of embryos. Zygotic embryo showed the proteins expression of isoelectric point between 4 to 7 and 7 to 10, and molecular weights between 25 to 36 KDa, which were not expressed in the cotyledonal somatic embryo. The low protein content during the development of the somatic embryos, particularly at the cotyledonary stage, is a factor that could be related with the low rate of conversion to plantlets and the high frequency of deformed somatic embryos of C. chinense.

Key words: Recalcitrance, maturation, germination, conversion.