A novel method for induction of plant regeneration via somatic embryogenesis

To induce plant regeneration via somatic embryogenesis, a binary expression vector system was constructed containing a heat shock-inducible FRT/FLP system. In this system, the BABY BOOM (BBM) gene, which shows similarity to the AP2/ERF family, was under the control of cauliflower mosaic virus 35S (CaMV 35S) promoter and the gene coding for FLP site-specific recombinase was under the control of a heat shock-inducible promoter HSP18.2 from Arabidopsis thaliana. The promoters and genes were flanked by two FRT recombination sites in direct orientation. BBM overexpression induced formation of somatic embryos from calli of Chinese white poplar (Populus tomentosa Carr.). Six somatic embryos germinated to form transgenic plants with phenotypic alterations. The stem cuttings of the transgenic plants were treated with heat shock and they developed into phenotypically normal plants. Southern blot analysis further confirmed that the BBM gene was excised from the genomic DNA of the transgenic plants with normal phenotype. The system reported here can be used to obtain transgenic plants without the use of antibiotic or herbicide resistance genes and to provide a novel strategy for plant regeneration via somatic embryogenesis. (C) 2009 Elsevier Ireland Ltd. All rights reserved.