Expression of a Cecropin B lytic peptide analog in transgenic tobacco confers enhanced resistance to bacterial wilt caused by Pseudomonas solanacearum

Cecropin B is a naturally-occurring lytic peptide found in Hyalophora cecropia, the Giant Silk Moth. It is thought to comprise part of an inducible humoral defense system that combats infection in the insect. Two 38 amino acid peptides, SB-37 and Shiva-1, were produced as substitution analogs of Cecropin B. SB-37 is 95% homologous to Cecropin B while Shiva-1 retains only 46% homology to the natural molecule. However, hydrophobic properties and charge density of the native structure were conserved at 100% in the synthetic peptides. The genes for both peptides were chemically synthesized and cloned into the binary vector pBI121 under the control of a constitutive or wound-inducible plant promoter. Transgenic tobacco plants (RO) were subsequently obtained via Agrobacterium transformation. Bioassays to test disease resistance of R1 progeny indicate that, compared to transgenic control and SB-37 plants, Shiva-1 seedlings exhibited delayed wilt symptoms and reduced disease severity and mortality after infection with a highly virulent strain of Pseudomonas solanacearum.