The rapid induction of glutathione S-transferases AtGSTF2 and AtGSTF6 by avirulent Pseudomonas syringae is the result of combined salicylic acid and ethylene signaling.
The expression of two members of the glutathione S-transferase (GST) multigene family was studied in Arabidopsis plants inoculated with an avirulent strain of Pseudomonas syringae pv. tomato (Pst). Accumulation of AtGSTF2 and AtGSTF6 transcripts started 4 and 2 h after inoculation, respectively, and clearly preceded the induction of the pathogenesis-related PR-1 gene. The aim of this work was to find the reason for the faster induction of the two GSTs compared with classical salicylic acid (SA)-regulated PR-proteins. Expression studies in Pst-inoculated SA-signaling mutants NahG and npr1 revealed that induction of both GSTs was SA-dependent and partially NPR1-independent. The induction of AtGSTF2 by Pst was also strongly repressed in the ethylene insensitive etr1 mutant. Both GSTs were induced by low amounts of SA (0.1 mM) and ethylene (0.1 ppm) while PR-1 gene expression was unaffected by ethylene. Interestingly, ethylene was about 50-fold less effective in NahG compared with wild-type plants thus suggesting a potentiation effect of SA on ethylene-induced accumulation of AtGST transcripts. Increased AtGST expression in plants inoculated with Pst correlated with increased production of SA and ethylene. However, the initial phase of AtGSTF6 induction was independent of SA- and ethylene-signaling. The jasmonate (JA)-insensitive mutant jar1 showed normal induction kinetics for both GSTs. Our data support the hypothesis that full expression of the pathogen-induced AtGSTF2 and, to a lesser extent AtGSTF6, is the result of combined SA- and ethylene-signaling and that early AtGSTF6 expression depends on additional unknown signaling mechanisms.
Lieberherr
Damien
D
Département de Biologie, Université de Fribourg, CH-1700 Fribourg, Switzerland. damien@bs.aist-nara.ac.jp
Wagner
Ulrich
U
Dubuis
Pierre-Henri
PH
Métraux
Jean-Pierre
JP
Mauch
Felix
F
D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D004790:Enzyme Induction / Q000187:drug effects; D005030:Ethylenes / Q000378:metabolism / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005982:Glutathione Transferase / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011549:Pseudomonas / Q000254:growth & development*; D020156:Salicylic Acid / Q000378:metabolism / Q000494:pharmacology*; D015398:Signal Transduction
D029681:Arabidopsis Proteins; D005030:Ethylenes; D005982:Glutathione Transferase; D010940:Plant Proteins; D020156:Salicylic Acid; C053376:pathogenesis-related proteins, plant; C036216:ethylene; C478066:GSTF2 protein, Arabidopsis; C478067:At1g02930 protein, Arabidopsis