Cysteine proteinases of Nicotiana benthamiana after inoculation with Colletotrichum destructivum or Pseudomonas syringae

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Hao, Lixin
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University of Guelph

Two papain family cysteine proteinase genes, 'NbCYP1' and 'NbCYP2', and a metacaspase type II gene, 'NbMCA1 ', were amplified from cDNA off. benthamiana infected with ' C. destructivum'. All three showed peak expression corresponding with the switch to necrotrophy by 'C. destructivum'. After inoculation with the incompatible bacterium, 'P. syringae' pv. ' tomato, NbCYP2' and 'NbMCA1' expression at 3 hours post inoculation increased, whereas expression of 'NbCYP1' decreased. Expression of all three then returned to near pre-inoculation levels and remained constant as necrosis later appeared due to a non-host hypersensitive response (HR). Virus-induced gene silencing of 'NbCYP1, NbCYP2' and 'NbMCA1' resulted in increased susceptibility of ' N. benthamiana' to 'C. destructivum' but did not affect HR necrosis or population levels of 'P. syringae' pv. ' tomato'. These cysteine protenase genes do not appear to be involved in the programmed cell death of HR resistance to 'P. syringae' but may limit the susceptibility to 'C. destructivum'.

papain family, cysteine proteinase genes, Nicotiana benthamiana, NbCYP1, NbCYP2, metacaspase type II gene, NbMCA1, Colletotrichum destructivum, Pseudomonas syringae