Background: Cecropin A is a natural antimicrobial peptide that exhibits rapid, potent and long-lasting lytic activity against a broad spectrum of pathogens, thus having great biotechnological potential. Here, we report a system for producing bioactive cecropin A in rice seeds. Results: Transgenic rice plants expressing a codon-optimized synthetic cecropin A gene drived by an endosperm-specific promoter, either the glutelin B1 or glutelin B4 promoter, were generated. The signal peptide sequence from either the glutelin B1 or the glutelin B4 were N-terminally fused to the coding sequence of the cecropin A. We also studied whether the presence of the KDEL endoplasmic reticulum retention signal at the C-terminal has an effect on cecropin A subcellular localization and accumulation. The transgenic rice plants showed stable transgene integration and inheritance. We show that cecropin A accumulates in protein storage bodies in the rice endosperm, particularly in type II protein bodies, supporting that the glutelin N-terminal signal peptides play a crucial role in directing the cecropin A to this organelle, independently of being tagged with the KDEL endoplasmic reticulum retention signal. The production of cecropin A in transgenic rice seeds did not affect seed viability or seedling growth. Furthermore, transgenic cecropin A seeds exhibited resistance to infection by fungal and bacterial pathogens (Fusarium verticillioides and Dickeya dadantii, respectively) indicating that the in planta-produced cecropin A is biologically active. Conclusions: Rice seeds can sustain bioactive cecropin A production and accumulation in protein bodies. The system might benefit the production of this antimicrobial agent for subsequent applications in crop protection and food preservation

This work was supported by SEPSAPE grants (Plant-KBBE programme) EUI2008-03769 and EUI2008-03572 from the Spanish Ministry of Science and Innovation, and ANR-08-KBBE-010 from the French Research Agency. We also thank the Consolider-Ingenio CSD2007-00036 award to CRAG and the Department d’Innovació, Universitats i Empresa of the Generalitat de Catalunya (Xarxa de Referencia en Biotecnología, Xarxa de Referència en Tecnologia dels Aliments, SGR09626, and 2008SGR812) for support. We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI)