Inactivation of the Lipoxygenase ZmLOX3 Increases Susceptibility of Maize to Aspergillus spp.

Abstract

Plant and fungal lipoxygenases catalyze the oxidation of polyunsaturated fatty acids, creating fatty acid hydroperoxides (oxylipins). Fungal oxylipins are required for normal fungal development and secondary metabolism, and plant host-derived oxylipins interfere with these processes in fungi, presumably by signal mimicry. The maize lipoxygenase gene ZmLOX3 has been implicated previously in seed-Aspergillus interactions, so we tested the interactions of a mutant maize line (lox3–4, in which ZmLOX3 is disrupted) with the mycotoxigenic seed-infecting fungi Aspergillus flavus and Aspergillus nidulans. The lox3–4 mutant was more susceptible than wild type maize to both Aspergillus species. All strains of A. flavus and A. nidulans produced more conidia and aflatoxin (or the precursor sterigmatocystin) on lox3–4 kernels than on wild type kernels, in vitro and under field conditions. Although oxylipins did not differ detectably between A. flavus-infected kernels of the lox3–4 and WT maize, oxylipin precursors (free fatty acids) and a downstream metabolite (jasmonic acid) accumulated to greater levels in lox3–4 than in WT kernels. The increased resistance of the lox3–4 mutant to other fungal pathogens (Fusarium, Colletotrichum, Cochliobolus, and Exserohilum) is in sharp contrast with results described herein for Aspergillus, suggesting that outcomes of lipoxygenase-governed host-pathogen interactions are pathogen-specific.

Root-Derived Oxylipins Promote Green Peach Aphid Performance on Arabidopsis Foliage

“…9-LOX-derived oxylipins are also involved in plant growth and development and in stress response. For example, 9-LOX-derived oxylipins are involved in lateral root development in Arabidopsis and maize (Zea mays) (Vellosillo et al, 2007;Gao et al, 2008) and in defense against bacterial pathogens in pepper (Capsicum annuum) and Arabidopsis (Vellosillo et al, 2007;Hwang and Hwang, 2010;Ló pez et al, 2011) and against fungal pathogens and nematodes in maize (Gao et al, 2007;Gao et al, 2008;Gao et al, 2009).…”

The Pepper 9-Lipoxygenase GeneCaLOX1Functions in Defense and Cell Death Responses to Microbial Pathogens

“…Gao et al (2007) recently suggested that oxylipin metabolism mediated by a specific 9-LOX, ZmLOX3, may be involved in fungal pathogenesis in maize (Zea mays). ZmLOX3 loss-of-function mutants are susceptible to Aspergillus flavus and Aspergillus nidulans infection (Gao et al, 2009).…”

PAMP Signaling in Plant Innate Immunity

“…Brassinosteroids (BR), a class of plant hormone with essential roles in plant growth and development, are perceived by LRR-RK BRI1, which is structurally similar to the PRR FLS2 (Belkhadir et al 2006 ). BAK1 is a positive regulator of PAMP-triggered plant immunity and it acts as an adaptor of multiple LRR-RKs that act in defense signaling, including the PRRs FLS2, EFR, PEPR1 and PEPR2 (Chinchilla et al 2007a , b ;Ryan et al 2007 ;Gao et al 2009a ;Postel et al 2010 ;Schulze et al 2010 ). It also acts as an adaptor of the receptor kinases BIR1 and SOBIR1, which seem to act as part of a presumed PRR complex(es) and/or at a downstream step in the signaling cascade (Saijo 2010 ).…”

“…It also acts as an adaptor of the receptor kinases BIR1 and SOBIR1, which seem to act as part of a presumed PRR complex(es) and/or at a downstream step in the signaling cascade (Saijo 2010 ). BAK1 forms a complex with the RLK BIR1 to negatively regulate defense responses (Gao et al 2009a ). BIK1 is a receptor-like cytoplasmic kinase (RLCK).…”