Grapevine and somatic embryogenesis: molecular approaches to uncover the genotype effect.

Somatic embryogenesis is the initiation of embryos from plant somatic tissues. This morphological event occurs spontaneously in some plant species and is usually induced in tissue cultures, either directly from the explants or after the callus stage. Today the somatic embryogenesis is one of the most suitable tools for the application of in vitro manipulation in the Vitis genus (e.g. stable genetic transformation, genome editing). In grapevine it is affected by many factors and the most important is undoubtedly the genotype. The behaviour of two grapevine genotypes during in vitro somatic embryogenesis has been investigated by profiling mRNAs and methylated DNA with high-throughput sequencing technologies. As a regeneration system known to exploit genotype-dependent reactions to growth conditions, somatic embryogenesis maximizes the potential of a single genotype to express its phenotypic plasticity, and it represents a powerful tool to explore this potential. Our previous studies showed as Sangiovese is a cultivar characterized by a high aptitude for embryogenesis, whereas Cabernet Sauvignon shows a lower one. Embryogenic tissues were induced from immature stamens excised from field-collected flower clusters of both cultivars and cultured on a callus induction medium. Three months after the initiation of the culture, we classified the calli as embryogenic or non-embryogenic. Transcriptome has been analyzed in the starting explants, and both transcriptome and methylome analyses are ongoing on undifferentiated calli induced after 40 days of culture, and in embryogenic and non-embryogenic calli after 3 months of culture. Aim of the study is then to analyze the reorganization of gene expression and epigenetic state that can be ascribed to the process of embryogenesis, and to identify the key regulators of somatic embryogenesis in different grapevine genotypes.