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Ellinger D, Stingl N, Kubigsteltig II, Bals T, Juenger M, Pollmann S, Berger S, Schuenemann D, Mueller MJ: DGL and DAD1 lipases are not essential for wound- and pathogen-induced jasmonate biosynthesis: redundant lipases contribute to jasmonate formation. Plant Physiol. 2010 Mar 26.
Lipases are involved in the generation of jasmonates which regulate responses to biotic and abiotic stresses. Two sn-1 specific acyl hydrolases, DAD1 and DGL, have been reported to be localized in plastids and to be essential and sufficient for jasmonate biosynthesis in Arabidopsis leaves. Here we show that levels of 12-oxo-phytodienoic acid (OPDA) and jasmonic acid (JA) in three different DGL-RNAi lines and the dad1 mutant were similar to wild type levels during the early wound response as well as after Pseudomonas infection. Due to the lack of sn-2 substrate specificity, synthesis of dinor OPDA was not expected and also not found to be affected in DGL-knockdown and overexpressing lines. As reported, DAD1 participates in jasmonate formation only in the late wound response. In addition, DGL protein was found to be localized in lipid bodies and not in plastids. Furthermore, jasmonate levels in 16 additional mutants defective in the expression of lipases with predicted chloroplast localization did not show strong differences to wild type levels after wounding except for a PLA-Igamma1 (At1g06800) mutant line that displayed diminished wound-induced dinor OPDA, OPDA and JA levels. A quadruple mutant defective in four DAD1-like lipases displayed similar jasmonate levels as mutant line of PLA-Igamma1 after wounding. Hence, we identify PLA-Igamma1 as a novel target gene to manipulate jasmonate biosynthesis. Our results suggest that, in addition to DAD1 and PLA-Igamma1, still unidentified enzymes with sn-1 and sn-2 hydrolase activity are involved in wound- and pathogen-induced jasmonate formation indicating functional redundancy within the lipase family. |
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