Dynamics of physiological and biochemical changes during somatic embryogenesis of Acca sellowiana

Feijoa (Acca sellowiana [O. Berg] Burret [Myrtaceae]) is a native fruit species of southern Brazil and northern Uruguay. This species is amenable to somatic embryogenesis and therefore suitable as a model system for comparative studies of zygotic and somatic embryo development. In seed plants, embryogenesis involves three main steps, which are regulated by many factors, such as hormones, proteins, polyamines, and transcription factors. In the present work, the dynamics of protein, sugar, starch, amino acid, and polyamine accumulation were assayed during somatic embryogenesis of A. sellowiana. Protein, starch, amino acid, and polyamine levels accumulated unevenly during the induction phase of somatic embryogenesis, while the sugar content remained stable. Throughout the different developmental stages of somatic embryogenesis, synthesis and accumulation of proteins and amino acids showed patterns similar to those reported previously during the development of zygotic embryos of this same species. Differential patterns of polyamine accumulation were observed. This is important because these compounds affect the synthesis of other endogenous growth regulators, such as auxinindole-3-acetic acid that is mainly involved in the establishment of embryo polarity. Taken together, the present work brings new insights to the physiological and biochemical dynamics that occur during somatic embryogenesis of A. sellowiana.