INCOMPATIBLE PATHOGEN INFECTION RESULTS IN ENHANCED REACTIVE OXYGEN AND CELL-DEATH RESPONSES IN TRANSGENIC TOBACCO EXPRESSING A HYPERACTIVEMUTANT CALMODULIN
Sa. Harding et Dm. Roberts, INCOMPATIBLE PATHOGEN INFECTION RESULTS IN ENHANCED REACTIVE OXYGEN AND CELL-DEATH RESPONSES IN TRANSGENIC TOBACCO EXPRESSING A HYPERACTIVEMUTANT CALMODULIN, Planta, 206(2), 1998, pp. 253-258
Transgenic tobacco (Nicotiana tabacum L. cv. Wisconsin 38) lines expre
ssing a mutant calmodulin (VU-3) that hyperactivates NAD kinase exhibi
t an enhanced elicitor-stimulated oxidative-burst reaction (S.A. Hardi
ng et al., 1997, EMBO J. 16. 1137-1144). VU-3 transgenic tobacco was u
sed in the present study to investigate the relationship between calmo
dulin signalling, the production of active oxygen species and cell dea
th in response to infection with an incompatible pathogen. Following P
. syringae pv. syringae 61 infection, suspension cells derived from VU
-3 transgenic plants exhibited a stronger oxidative burst (3- to 4-fol
d higher primary and secondary burst reactions), greater media alkalin
ization (3-fold) and more rapid cell death (4-fold greater mortality a
t 20 h post infection) than did infected control tobacco cells. Infect
ion of leaf tissues with P. syringae pv. syringae 61 also resulted in
an enhanced cell death response compared to control tobacco tissues. T
his cell death response of VU-3 leaf tissues, but not control leaf tis
sues, was further enhanced by the presence of 50 mu M salicylic acid,
suggesting that this transgenic line is more sensitive to the effects
of this agent. Overall, the data support the model that calmodulin sig
nalling pathways are involved in the plant oxidative burst and contrib
ute to the regulation of cell death in infected plant tissues undergoi
ng the hypersensitive response.