Rhizobacteria-mediated induced systemic resistance (ISR) in Arabidopsis isnot associated with a direct effect on expression of known defense-relatedgenes but stimulates the expression of the jasmonate-inducible gene Atvsp upon challenge
Scm. Van Wees et al., Rhizobacteria-mediated induced systemic resistance (ISR) in Arabidopsis isnot associated with a direct effect on expression of known defense-relatedgenes but stimulates the expression of the jasmonate-inducible gene Atvsp upon challenge, PLANT MOL B, 41(4), 1999, pp. 537-549
Selected strains of nonpathogenic rhizobacteria from the genus Pseudomonas
are capable of eliciting broad-spectrum induced systemic resistance (ISR) i
n plants that is phenotypically similar to pathogen-induced systemic acquir
ed resistance (SAR). In Arabidopsis, the ISR pathway functions independentl
y of salicylic acid (SA) but requires responsiveness to jasmonate and ethyl
ene. Here, we demonstrate that known defense-related genes, i.e. the SA-res
ponsive genes PR-1, PR-2, and PR-5, the ethylene-inducible gene Hel, the et
hylene- and jasmonate-responsive genes ChiB and Pdf1.2, and the jasmonate-i
nducible genes Atvsp, Lox1, Lox2, Pal1, and Pin2, are neither induced local
ly in the roots nor systemically in the leaves upon induction of ISR by Pse
udomonas fluorescens WCS417r. In contrast, plants infected with the virulen
t leaf pathogen Pseudomonas syringae pv. tomato (Pst) or expressing SAR ind
uced by preinfecting lower leaves with the avirulent pathogen Pst(avrRpt2)
exhibit elevated expression levels of most of the defense-related genes stu
died. Upon challenge inoculation with Pst, PR gene transcripts accumulated
to a higher level in SAR-expressing plants than in control-treated and ISR-
expressing plants, indicating that SAR involves potentiation of SA-responsi
ve PR gene expression. In contrast, pathogen challenge of ISR-expressing pl
ants led to an enhanced level of Atvsp transcript accumulation. The other j
asmonate-responsive defense-related genes studied were not potentiated duri
ng ISR, indicating that ISR is associated with the potentiation of specific
jasmonate-responsive genes.