Abstract
The jasmonate family of phytohormones, as represented by 12-oxo-phytodienoic acid (OPDA), dinor-phytodienoic acid (dn-OPDA), and jasmonic acid in Arabidopsis (Arabidopsis thaliana), has been implicated in a vast array of different developmental processes and stress responses. Recent reports indicate that OPDA and dn-OPDA occur not only as free acids in Arabidopsis, but also as esters with complex lipids, so-called arabidopsides. Recently, we showed that recognition of the two bacterial effector proteins AvrRpm1 and AvrRpt2 induced high levels of a molecule consisting of two OPDAs and one dn-OPDA esterified to a monogalactosyl diacylglycerol moiety, named arabidopside E. In this study, we demonstrate that the synthesis of arabidopsides is mainly independent of the prokaryotic lipid biosynthesis pathway in the chloroplast, and, in addition to what previously has been reported, arabidopside E as well as an all-OPDA analog, arabidopside G, described here accumulated during the hypersensitive response and in response to wounding. We also show that different signaling pathways lead to the formation of arabidopsides during the hypersensitive response and the wounding response, respectively. However, the formation of arabidopsides during both responses is dependent on an intact jasmonate signaling pathway. Additionally, we report inhibition of growth of the fungal necrotrophic pathogen Botrytis cinerea and in planta release of free jasmonates in a time frame that overlaps with the observed reduction of arabidopside levels. Thus, arabidopsides may have a dual function: as antipathogenic substances and as storage compounds that allow the slow release of free jasmonates.
Highlights
The jasmonate family of phytohormones, as represented by 12-oxo-phytodienoic acid (OPDA), dinor-phytodienoic acid, and jasmonic acid in Arabidopsis (Arabidopsis thaliana), has been implicated in a vast array of different developmental processes and stress responses
The jasmonates have been implicated in a vast array of different developmental processes and stress responses (Blee, 2002; Feussner and Wasternack, 2002; Howe and Schilmiller, 2002; Wasternack, 2007)
Several reports indicate that OPDA and dn-OPDA occur as free acids in Arabidopsis (Arabidopsis thaliana) tissue and as esters with complex lipids (Stelmach et al, 2001; Hisamatsu et al, 2003; Hisamatsu et al, 2005; Andersson et al, 2006a; Buseman et al, 2006)
Summary
The jasmonate family of phytohormones, as represented by 12-oxo-phytodienoic acid (OPDA), dinor-phytodienoic acid (dnOPDA), and jasmonic acid in Arabidopsis (Arabidopsis thaliana), has been implicated in a vast array of different developmental processes and stress responses. The different OPDA- and dn-OPDA-containing galactolipids were recently reported to accumulate after wounding of Arabidopsis leaves (Buseman et al, 2006; Bottcher and Weiler, 2007). Recognition of AvrRpm1 and AvrRpt2, like wounding, induced accumulation of very high levels of galactolipid-bound OPDA and dn-OPDA.
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