Open AccessGene Expression Is Not Systematically Linked to Phytoalexin Production During Alfalfa Leaf Interaction with Pathogenic Bacteria
Author(s) -
Christophe Sallaud,
José Ângelo Silveira Zuanazzi,
Joumana El-Turk,
Juliette Leymarie,
C. Breda,
Dominique Buffard,
Isabelle de Kozak,
Pascal Ratet,
Philippe Husson,
Ádám Kondorosi,
R. Esnault
Publication year - 1997
Publication title -
molecular plant-microbe interactions
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.565
H-Index - 153
eISSN - 1943-7706
pISSN - 0894-0282
DOI - 10.1094/mpmi.1997.10.2.257
Subject(s) - phytoalexin , chalcone synthase , isoflavonoid , chalcone isomerase , biology , xanthomonas campestris , biosynthesis , flavonoid biosynthesis , reductase , chalcone , pseudomonas syringae , gene , biochemistry , botany , gene expression , flavonoid , enzyme , chemistry , transcriptome , stereochemistry , antioxidant , resveratrol
During an incompatible interaction between alfalfa leaves and Pseudomonas syringae pv. pisi, flavonoids accumulated between 6 and 24 h, whereas they could not be detected during the first 96 h of a compatible interaction with Xanthomonas campestris pv. alfalfae. Three flavonoids accumulated which were identified as 4′,7-dihydroxyflavanone and 4′,7-dihydroxyflavone and 2′,4,4′-trihydroxychalcone. Surprisingly, the phytoalexin medicarpin was found only at a very low level. Analysis of both the infected and noninfected zones revealed that these flavonoids were detectable only in the infiltrated tissue. Northern hybridizations showed that transcripts encoding for chalcone synthase (CHS), chalcone reductase, chalcone isomerase, and isoflavone reductase (IFR) accumulated in both infiltrated and noninfiltrated zones. Measurements of the CHS and IFR activities in the infiltrated and noninfiltrated zones indicated that the levels of CHS activity were highly increased only in the infiltrated zones, whereas the levels of IFR were very slightly stimulated. These results suggested that an apparently coordinated expression of genes, involved in both the early and late steps of isoflavonoid biosynthesis, is not a sufficient condition for phytoalexin accumulation and that the fundamental regulatory steps might act at the post-transcriptional level.