Exploring the involvement of the somatic embryogenesis receptor kinase (SERK) gene family in olive somatic embryogenesis efficiency

Abstract

Several Portuguese olive tree cultivars are characterized by their high-quality oils, which explains their use on the production of DOP (Denomination of Protect Origin) olive oil brands. However, some of those cultivars are affected by serious agronomic problems, including high susceptibility to biotic and abiotic stresses, excessive vigour, and low ability to adventitious root formation, which strongly limits its propagation by cuttings. The establishment of somatic embryogenesis (SE) protocols can work as an alternative for propagation of those cultivars. Nevertheless, the efficiency of SE strongly depends on the complex interaction between numerous factors, including amongst others the genotype of the donor plant, the type of explant used to establish the in vitro cultures and its developmental stage. Plant regeneration through SE involves changes in gene expression and has been associated with changes in DNA methylation in several model plants, but little is known about the genes expressed during SE in olive. Somatic embryogenesis receptor kinase (SERK) belongs to a small family of receptor-like kinases involved in signal transduction in various plant species. In the present research, the involvement of SERK members in SE efficiency was evaluated by using two olive somatic embryogenic lines, characterized by their different ability to differentiate somatic embryos (high and low-efficient lines). In vitro cultured calli from both lines were stimulated to undergo cyclic embryogenesis by inoculation on Olive Cyclic Embryogenic liquid medium. Samples from the cell lines were collected at 7 days and further used for total RNA extraction and cDNA synthesis. The involvement of SERK gene family members was evaluated by RT-qPCR and the results achieved revealed a different regulation when comparing high and low efficient cell lines. Differences between timepoints were also detected. The involvement of epigenetic events specifically related with methylation events will be considered in further research.