Hydroperoxide lyase depletion in transgenic potato plants leads to an increase in aphid performance

Abstract

Hydroperoxide lyases (HPLs) catalyze the cleavage of fatty acid hydroperoxides to aldehydes and oxoacids. These volatile aldehydes play a major role in forming the aroma of many plant fruits and flowers. In addition, they have antimicrobial activity in vitro and thus are thought to be involved in the plant defense response against pest and pathogen attack. An HPL activity present in potato leaves has been characterized and shown to cleave specifically 13-hydroperoxides of both linoleic and linolenic acids to yield hexanal and 3-hexenal, respectively, and 12-oxo-dodecenoic acid. A cDNA encoding this HPL has been isolated and used to monitor gene expression in healthy and mechanically damaged potato plants. HPL gene expression is subject to developmental control, being high in young leaves and attenuated in older ones, and it is induced weakly by wounding. HPL enzymatic activity, nevertheless, remains constant in leaves of different ages and also after wounding, suggesting that posttranscriptional mechanisms may regulate its activity levels. Antisense-mediated HPL depletion in transgenic potato plants has identified this enzyme as a major route of 13-fatty acid hydroperoxide degradation in the leaves. Although these transgenic plants have highly reduced levels of both hexanal and 3-hexenal, they show no phenotypic differences compared with wild-type ones, particularly in regard to the expression of wound-induced genes. However, aphids feeding on the HPL-depleted plants display approximately a two-fold increase in fecundity above those feeding on nontransformed plants, consistent with the hypothesis that HPL-derived products have a negative impact on aphid performance. Thus, HPL-catalyzed production of C6 aldehydes may be a key step of a built-in resistance mechanism of plants against some sucking insect pests.

Variations in CYP74B2 (Hydroperoxide Lyase) Gene Expression Differentially Affect Hexenal Signaling in the Columbia and Landsberg erecta Ecotypes of Arabidopsis

“…Previous work has shown that the relationship between these branches is far beyond that of two similar enzymes competing for the same substrate and suggestive of transcriptional cross-talk between activators of these branched pathways (Halitschke et al, 2004). Initiated with antisense depletion strategies in transgenic potato and tobacco plants that provided the first information on the physiological effects of reducing CYP74B2 expression (Vancanneyt et al, 2001;Halitschke et al, 2004), our discovery of a natural frame-shift deletion in the CYP74B2 locus extends this depletion analysis to analysis of plants completely eliminating functional CYP74B2 activity. We find no evidence for compensation between the HPL and AOS branches of this pathway; when HPL activity is not expressed in the Col ecotype, there is no significant increase in AOS or any of four AOC transcripts needed for synthesis of JA.…”

“…The fact that transcripts from these loci are also induced in herbivoredamaged plants (Reymond et al, 2004) and depleted in the Col ecotype suggests that they also exist downstream of the HPL pathway activated in plant-insect interactions. The immediate effects on insect resistance of inactivating the HPL pathway are complexed by the fact that GLVs have the ability to affect herbivore performance both negatively (by reducing feeding rate, repelling oviposition, or attracting predators; Hildebrand et al, 1993;DeMoraes et al, 2001;Kessler and Baldwin, 2001;Vancanneyt et al, 2001) and positively (by serving as feeding stimulants; Halitschke et al, 2004). Further comparison of the differences in the responses of the Col and Ler ecotypes to herbivore damage will provide more insight into the necessity of having a functional HPL branch in the oxylipin pathway.…”

Lipid metabolism in arbuscular mycorrhizal roots of Medicago truncatula

“…In Arabidopsis thaliana two members of this enzyme family were found, a 13-AOS and a 13-HPL. Moreover, in potato two other isoforms have been described to date, a 9-DES and a 13-HPL Vancanneyt et al, 2001). In order to understand the complex system of CYP74 enzymes and the function of oxylipins in potato, we aimed to identify additional CYP74 enzymes in potato by screening EST databases (www.tigr.org/tdb/lgi).…”

“…Different C6-volatiles have been shown to induce defence related genes and to stimulate phytoalexin accumulation (Zeringue, 1992;Bate and Rothstein, 1998). In transgenic potato plants lacking HPL transcript an increase in aphid performance was observed (Vancanneyt et al, 2001). Up to now the effect of C9-volatiles has not been investigated.…”

Lipid and oxylipin profiles during aging and sprout development in potato tubers (Solanum tuberosum L.)

“…Colneleic acid is clearly involved in plant defence against pathogens [6,14] and is also an inhibitor of LOX activity [33], but this work is the first indication for a role of colneleic acid during the normal life cycle of the tuber, and for a potential role of colneleic acid in sprout development. It is unlikely that the 9-oxo-nonanoic acid methyl ester in the extracts was formed by the action of HPO lyase on 9-HPOD and HPOT, because it has been demonstrated that potato tuber HPO lyase is specific for 13-HPOD and HPOT [30,34], and the tubers contained little 13-HPOD and HPOT. Moreover, HPO lyase activity rapidly drops to zero during tuber storage [30].…”