Callus induction in Araucaria angustifolia using orthotropic and plagiotropic apexes: proteomic and morphoanatomical aspects

Araucaria angustifolia is a conifer with relevant economic importance and is fundamental for the ecological and ethnoecological relationships of the regions it inhabits. However, the Araucaria forest is highly fragmented and in critical danger of extinction due to its indiscriminate exploitation. Somatic embryogenesis (SE) is a promising morphogenetic route that allows conservation and mass propagation, in addition to serving as a model for fundamental studies of plant morphology, physiology, and biochemistry. In A. angustifolia SE, zygotic embryos are the traditional type of explant used, despite the great limitation of seed availability at different times of the year and the impossibility of cloning genotypes of interest. In this context, this work aimed to establish callus of A. angustifolia using orthotropic and plagiotropic apexes as initial explants and, based on morphological and proteomic analyses, investigate the possible embryogenic potential of these cultures. The results showed that the orthotropic and plagiotropic apexes could generate homogeneous callus cultures, although morphologically different from each other with regard to cell size and compounds deposition. Proteomic analysis indicated high translation rates in orthotropic calli , indicating intense metabolic activity. The plagiotropic calli , in turn, revealed a refined mechanism of remediation of proteotoxic stress. From the data generated by the proteomic analysis, it was also possible to map proteins that are considered molecular markers of the induction of somatic embryogenesis in A. angustifolia and other plant species, such as heat shock proteins, showing the possible embryogenic potential of these cultures by both biochemical and morphoanatomical analyses.