Regeneration of transgenic papaya plants via somatic embryogenesis induced by Agrobacterium rhizogenes

An Agrobacterium rhizogenes-mediated procedure for transformation of papaya (Carica papaya) was developed. Transgenic plants were obtained from somatic embryos that spontaneously formed at the base of transformed roots, induced from leaf discs infected with A. rhizogenes. Transformation was monitored by autonomous growth of roots and somatic embryos, resistance to kanamycin, β-glucuronidase activity (GUS), and Southern hybridization analysis. Over one-third of the infected leaf explants produced transformed roots with GUS activity, from which 10% spontaneously produced somatic embryos. Histological analysis of A. rhizogenes-transformed embryos showed that they have an altered symmetry between the shoot apex and the root meristem when compared to somatic embryos induced with hormone treatment from control explants. Transgenic papaya plants containing A. rhizogenes rol genes were more sensitive to auxins, developed wrinkled leaves, and grew slower than nontransformed plants.