9-Lipoxygenase metabolism is involved in the almond/Aspergillus carbonarius interaction

Abstract

Phyto-oxylipins are a group of biologically active molecules that play an important role in plant defence. Their production begins with the oxygenation of polyunsaturated fatty acids by lipoxygenases (LOX) to form 9- or 13-hydroperoxides that are substrates for several enzymes involved in the synthesis of final oxylipins, which can act as signal molecules and/or direct antimicrobials. In the present work, the response of the 9-LOX pathway in the almond/Aspergillus carbonarius (producer of ochratoxin A) interaction was studied. Both LOX gene expression and activity are up-regulated over the course of fungal infection in immature and mature almonds. The biochemical characterization of major LOX and hydroperoxide lyase (HPL) isoforms indicated that 9-LOX metabolism is specifically induced by A. carbonarius. Lipid peroxidation profiling showed that, in infected immature almonds, enzymatically produced 9-hydro(peroxy) fatty acids (HFAs) were the main HFAs and are further metabolized by HPL into C9-aldehydes. Both HPL gene expression and C9-aldehydes increased over the course of fungal infection. In mature almonds infected with A. carbonarius, levels of LOX expression and activity were lower than those found in immature seeds, and 9-HFA represented the minority of total HFA, which consisted of mostly 13- and non-enzymatically produced HFA. In these experimental conditions, no volatile aldehydes were recorded from these samples, even though HPL was up-regulated in infected mature almonds. The effects on the growth of A. carbonarius of the aldehydes produced by these enzymes were also tested in vitro. Results reported here led to the proposal that, in almond seed, the association of 9-LOX and HPL has an important role in seed defence mechanism against pathogen infection.

Identifying differentially expressed genes in leaves of Glycine tomentella in the presence of the fungal pathogen Phakopsora pachyrhizi

“…Thus far, identified phyto-oxylipins are synthesized via the lipoxygenase, cytochrome P450 monooxygenase, and a-dioxygenase pathways (Mita et al 2007;Blee et al 2002). Interestingly in this study, abundance of cytochrome P450 monoxygenase and lipoxygenase transcripts are higher in the susceptible genotype (GT-05) than in the resistant genotype (GT-06), whereas, the reverse is true for a-dioxygenase gene.…”

“…In plant cells, oxylipins are compounds that play important roles in several physiological events including plant defense, development, and senescence (Mita et al 2007). Thus far, identified phyto-oxylipins are synthesized via the lipoxygenase, cytochrome P450 monooxygenase, and a-dioxygenase pathways (Mita et al 2007;Blee et al 2002).…”

Comparative molecular and biochemical characterization of segmentally duplicated 9-lipoxygenase genes ZmLOX4 and ZmLOX5 of maize

“…Recent studies reported that bacteria-induced hypersensitive response (HR), a form of a programmed cell death executed by the host during incompatible interactions with pathogens, may be mediated by 9-LOXs in cotton and pepper plants (Cacas et al 2009;Hwang and Hwang 2009). 9-LOXs are implicated in seed defense mechanism in response to infection by mycotoxin-producing Aspergillus Xavus in almond (Mita et al 2007) and maize (Gao et al 2009). Accumulating evidence suggest that some 9-LOXs have a role in plant developmental processes.…”

Acaricidal effects of natural six-carbon and nine-carbon aldehydes on stored-product mites

“…The direct eVect of such compounds has been evaluated on various pathogens and pests (Hammond et al 2000;Prost et al 2005;Casey and Hughes 2004;Matsui 2006;Mita et al 2007;Hubert et al 2008). However, the eVect of plant volatile aldehydes on mites has not been reported so far.…”