Expression of C-terminal Prodomain Truncated Petunia Floral Defensins Inhibit the Growth of Transgenic Banana Plants

Plant defensins are basic proteins synthesized as part of innate immune response against the attack of fungal pathogens. These defensins show strong antimicrobial activity which is specifically directed towards the invading pathogen. Diverse defensins have been overexpressed in model transgenic plants to show their efficacy in heterologous systems. There are more than 350 plant defensins known today which have occurred due to convergent and divergent evolution over time. Although most of these peptides generally do not react with the host plant cells, some may have deleterious effect on plant organs. As a consequence plants build up advance strategy to nullify the effect by targeting the peptides to vacuoles, preventing its expression in sensitive organs and changing the amino acids composition. The C-terminal propeptide (CTPP) domains probably prevented any lethal effects of plant defensins while simultaneously enabling vacuolar sorting. In order to study the role of CTPP of two Petunia floral defensins (PhDef1-T and PhDef2-T), banana embryogenic cells were transformed with PhDef1-T and PhDef2-T without the CTPP domain region. The results obtained from this study clearly demonstrated that the absence of CTPP in Petunia floral defensins caused significant reduction in the number of embryos and its poor growth. Regenerated shoots were considerably slow in growth signifying the relevance and the importance of the prodomain region in floral defensins.