Mammalian growth-regulating factors enhance regeneration of recalcitrant transgenic tomato accessions

Genome editing is now available for many crops. It has increased our ability to study gene function and has changed the field of plant transgenesis. Nevertheless, the ability to regenerate plants from cell culture remains a limiting factor for many crops, and even for species with a good regeneration potential, some accessions remain recalcitrant. The physiological state of plant cells is involved in the process of plant growth and development and is closely linked to the network involving MAP-kinase signaling pathway. Some of the defense genes activated during the cellular repair process of transgenesis show high homologies with mammalian defense genes. We thus compared the percentage of transgenic plants obtained by CRISPR-Cas9 mutation in four genes involved in sugar and acid metabolism after supplementation with different mammalian growth factors and cytokines in six tomato accessions presenting a range of regeneration levels. We demonstrated, through three years of transgenesis experiments, that the use of mammalian growth factors during transgenesis improved regeneration rate of recalcitrant tomato accessions. We demonstrated that using cytokines not only improved transformation of difficult-to-transform accessions but also the production rate of stable secondary lines.