The selective induction of heat shock protein(s) (HSP) in human cells durin
g bacterial, parasitic or viral infection and the accompanying cytoprotecti
on initiated an interest in this conserved group of proteins - either as ma
rkers of disease outcome and severity or in novel therapeutic approaches. K
nowledge concerning the induction and role of HSP in plant-pathogen interac
tions is however limited. The objective of this study was to investigate th
e expression of constitutive and inducible members of the 70-kDa HSP family
(Hsp70/Hsc70) during compatible and incompatible interactions in tomato Ly
copersicon esculentum L. cv. UC82B. Cell suspensions were co-cultured with
virulent (biovar III) or avirulent (biovar II) strains of Ralstonia solanac
earum, the causative agent of bacterial wilt, and samples harvested at spec
ific time points for the analysis of pathogenesis-related protein-1 (PR-1)
accumulation, phenylalanine ammonia-lyase (EC 4.3.1.5, PAL) activity, Hsp70
/Hsc70 accumulation and cell survival. Besides inducing PRA (6-18 h, P < 0.
05), biovar II caused a virulence-dependent induction of Hsp70/Hsc70 (24-48
h, P < 0.05) coinciding with the induction of PAL activity (24-48 h, P < 0
.05) and maintenance of cell viability (48 h). It is proposed that, at leas
t in tomato, Hsp70/Hsc70 is induced by avirulent strains of R. solanacearum
as part of the defence response to chaperone newly synthesized defence pro
teins and to maintain cellular homeostasis essential for the execution of a
defence response. <(c)> 2001 Editions scientifiques et medicales Elsevier
SAS.