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Exploring the role of jasmonic acid amido synthetases in plant wound response
The Arabidopsis JAR1 locus encodes a JA amido synthetase (JAS) that conjugates jasmonic acid to several amino acids. However, the role of JAR1-like genes from other plant species in wound response was unknown. This study focused on the involvement of JAR1 in wound response of Arabidopsis and tomato. In wild type Arabidopsis the level of JAR1 transcript peaked one hour after wounding and was accompanied by a 25-fold increase in JA-Ile. Other JA conjugates remained near basal level or were undetected at all times following wounding. The rise in both JAR1 transcript and JA-Ile occurred at least 3 hr before the appearance of jasmonate-dependent VSP transcript. JA-Ile was about 6-fold lower in the jar1-1 mutant compared to wild type at all wounding time points and the mutant accumulated significantly less VSP transcript. Evaluation of wounding effect on JA-conjugate synthesis in lie overaccumulating mutant omr1 revealed that JA-Ile and the level of VSP transcript were also significantly reduced in this mutant. Analysis of the fad3-2fad7-1fad8, opr3 and coi1 mutants of Arabidopsis showed that the induction of JAR1 by wounding was largely independent of JA synthesis, but required the COI1 signaling component. Characterization of a tomato homologue of Arabidopsis JAR1 showed that the tomato JAS (LeJAR1) synthesized a similar spectrum of JA-conjugates in vitro, as did the Arabidopsis enzyme. Leaf wounding induced LeJAR1 transcript in a JA/1-dependent manner. However, in contrast with Arabidopsis JA-Ile accumulation preceded the increase of the LeJAR1 transcript following wounding. This suggested that in tomato the initial conjugate synthesis was dependent on factors other than transcriptional induction of LeJAR1 . Nevertheless, increase of both LeJAR1 transcript and JA-Ile preceded that of defensive proteinase inhibitor II transcript, suggesting JA-Ile may participate in wound response of tomato. An RNAi-mediated silencing of LeJAR1 resulted in identification of plants that accumulated reduced levels of LeJAR1 transcript following wounding. These results provide new evidence for the involvement of JA-Ile in modulating wound-responsive defense gene expression in both Arabidopsis and tomato. ^
Agriculture, Agronomy|Agriculture, Plant Pathology
Suza, Walter P, "Exploring the role of jasmonic acid amido synthetases in plant wound response" (2006). ETD collection for University of Nebraska - Lincoln. AAI3208083.