Putrescine induces somatic embryo development and proteomic changes in embryogenic callus of sugarcane

Somatic embryogenesis, an important biotechnological technique, has great potential for application in sugarcane breeding and micropropagation. Polyamines have been associated with the regulation of several physiological processes, including the acquisition of embryogenic competence and somatic embryogenesis. In this study, we used a proteomic approach to evaluate the effects of exogenous polyamine on sugarcane somatic embryo development to better understand this process. Embryogenic cultures were treated with different concentrations of putrescine, spermidine, and spermine. Proteomic analyses combined the shotgun method and the nanoESI-HDMS(E) technology. Among polyamines, 500 μM putrescine gave rise to the highest number of somatic embryos; however, no differences in the amount of fresh matter were observed between polyamines and control. Differences in protein abundance profiles resulting from the effect of 500 μM putrescine on sugarcane somatic embryo maturation were observed. Proteomic analyses of putrescine and control treatment showed differences in the abundances of proteins related to somatic embryogenesis, such as arabinogalactan proteins, peroxidases, heat shock proteins, glutathione s-transferases, late embryogenesis abundant proteins, and 14-3-3 proteins. These results show that putrescine and the identified proteins play important roles in protecting the cells against an in vitro stress environment, contributing to the formation of somatic embryos during the maturation treatment.

Despite all studies with somatic embryogenesis, the molecular mechanisms controlling the process have not been completely understood. In this study, we highlighted the effects of the polyamine putrescine on somatic embryogenesis of sugarcane and the differentially abundant proteins related to somatic embryo development. We identified six groups of important stress related proteins that are involved in the adaptation of cells to the stress environment of in vitro culture and may also be part of the mechanisms associated to the somatic embryogenesis process. Therefore, our research is trying to understand the complexity of how one single somatic cell becomes a whole plant.