Somatic embryogenesis as a biotechnological tool for grapevine breeding and functional genomics

Somatic embryogenesis (SE) is a morphogenetic process in which the plant regenerative potential is exploited to replicate a whole organism starting from somatic explants. During this process, differentiated somatic cells re-enter the cell cycle and transform into a dedifferentiated state, then acquire embryogenic potential characterized by the reprogramming of gene expression, metabolism and epigenetic status. SE in grapevine is an essential pre-requisite for the application of next-generation breeding techniques, although it is a highly genotype-dependent process, with different cultivars showing wide variations in their competence to form embryogenic issues. Moreover, SE process and in vitro culture can generate somaclonal variability, i.e. genetic variability resulting from gene mutations or epigenetic changes, which can be exploited for the purpose of genetic improvement. In the present contribution, we will discuss experimental works that use SE as a biotechnological tool for different purposes. We demonstrated that SE is an effective strategy for dissecting chimerism phenomena in a commercial relevant clone of 'Nebbiolo' and that the spread of chimerism in grapevine must be carefully considered in the framework of biotechnological improvement programmes. In addition, we demonstrated that SE is effective in the elimination of the complete virome in grapevine, including mycoviruses. This suggests that the "biological vacuum" generated by this regeneration technique also involves fungi, resulting in gnotobiotic or pseudo-gnotobiotic plants, thereby representing an extraordinary asset to understand the influence of the microbiome on plant growth and physiology. Ongoing results related to functional genomic studies aimed at deciphering the role of different miRNAs involved in the photosinthetic process and in response to pathogens, or the role of anthoMATE transporters will be discussed, as well as results emerging from the exploitation of spontaneous and induced somaclonal variation to obtain grapevine somaclones (from V. vinifera and rootstocks) with a higher degree of tolerance/resistance to biotic and abiotic stresses. Ongoing results related to the protocol fine-tuning and application of cisgenic and genome editing approaches via Agrobacterium transformation or by means of plant regeneration from protoplasts will be presented as well. Targeting miRNAs or downstream signaling components of traditional resistance genes would allow the development of cisgenic or edited plants with less specific resistance to a single pathogen, but more long-lasting resistance against several pathogens.