Genetic Transformation

The use of transformation technologies for Prunus crops has been rather modest when compared to the major commercialized genetically engineered crops, and the lack of efficient biotechnology platforms is considered to be the 'bottleneck' preventing the improvement of these species by through genetic transformation. In addition, dormancy and cold requirement are also relevant traits for an industry extremely impacted by climate change effects every season. Recently, we have designed several procedures for massive micropropagation of sweet cherry genotypes and their rootstocks using temporary immersion systems; these procedures accompanied the establishment of an organogenesis and transformation platform in some of these genotypes, which now is presented under a scenario in which Flowering locus T (FT) and Terminal flower 1 (TFL1) genes from P. avium L. were the experimental target. Several seed-derived explants were evaluated as starting point of transformation/regeneration procedures, and those corresponding to hypocotyls, epicotyls, embryo segments, and cotyledons, led to successful generation of transgenic Maxma-14, ‘Bing’, and ‘Rainier’ trees. Experiments included two transformation plasmids: a “FT-GFP” fusion, in which the flowering inductor previously evaluated in Arabidopsis plants led to Sch-FT overexpression; and “amiR-TFL1”, an artificial microRNA targeting the sweet cherry TFL1 gene, which generates a RNAi process against this flowering inhibitor. Currently, whereas none of the transformed trees have shown deregulated or increased flowering rate (as formerly expected) after a first cold cycle, several important architecture changes have been obtained in these transgenic materials. The results suggest the involvement of these genes in plant shape and also indicate that flowering process could be more complex than expected and that are probably associated or influenced by/to additional processes taking place in these trees, such as juvenility.