Expression ofCryptogein in tobacco plants exhibits enhanced disease resistance and tolerance to salt stress

Abstract

Cryptogein (Crypt), an elicitin secreted fromPhytophthora cryptogea, was used for genetic engineering of biotic and abiotic resistance plants. We generated transgenic tobacco plants harboring a rice phenylalanine ammonia-lyase (PAL) promoter andCrypt fusion gene (PAL::Crypt) or the mutatedCrypt (mutation of the lysine at the position 13 to valine) under the controlCaMV35S promoter (CaMV35S::CryK13V). T2 progeny of the transgenic plants showed significantly enhanced disease resistance to pathogens of fungalPhytophthora parasitica varnicotiana (Ppn) andAlternaria alternata, and bacterialPseudomonas syringae pvtabaci. The amount of mRNA accumulation ofCrypt andCryK13V was quite low in the transgenic lines analyzed by Northern blot, and was detected by a reverse transcription PCR method. Plants harboringPAL::Crypt construct showed faster and stronger induction ofPR1a gene afterPpn inoculation than that in the wild-type plants. The results suggested that the induciblePAL promoter could rapidly respond to pathogen attack and efficiently suppress the pathogen infection. Furthermore, the enhanced tolerance to salt stress in both of theCrypt andCryK13V expressing tobacco plants was also observed compared with that in the control plants. The constitutive expression ofPR and transcription factor genes in the transformants was probably associated with the salt tolerance. The above observations suggested that a cross-talk between biotic and abiotic stresses existed in tobacco plants.