Inducible expression of a Phytolacca heterotepala ribosome-inactivating protein leads to enhanced resistance against major fungal pathogens in tobacco

Plant genetic engineering, has long been considered a valuable tool to fight fungal pathogens because it would limit the economically costly and environmentally undesirable chemical methods of disease control. Ribosome-inactivating proteins (Rips) are potentially useful for plant defense considering their antiviral and antimicrobial activities but their use is limited by their cytotoxic activity. A new gene coding for in RIP isolated from leaves of Phytolacca heterotepala was expressed in tobacco under the control of the wound-inducible promoter of the bean polygalacturonase-inhibiting protein I gene to increase resistance against different fungal pathoaens, because an individual RIP isolated from P heterotepalo showed direct antifungal toxicity. Phenotypically normal transgenic lines infected with Alternaria alternata and Botrytis cinerea showed a significant reduction of leaf damage while reverse transcription-polymerase chain reaction and western analysis indicated the expression of the RIP transgene upon wounding and pathogen attack. This work demonstrates that use of a wound-inducible promoter is useful to limit the accumulation of antimicrobial phytotoxic proteins only in infected areas and that the controlled expression of the PhRIP I gene call be very effective to control fungal pathogens with different phytopathogenic actions.