title: The novel monocot-specific 9-lipoxygenase ZmLOX12 is required to mount an effective jasmonate-mediated defense against Fusarium verticillioides in maize.
abstract: Fusarium verticillioides is a major limiting factor for maize production due to ear and stalk rot and the contamination of seed with the carcinogenic mycotoxin fumonisin. While lipoxygenase (LOX)-derived oxylipins have been implicated in defense against diverse pathogens, their function in maize resistance against F. verticillioides is poorly understood. Here, we functionally characterized a novel maize 9-LOX gene, ZmLOX12. This gene is distantly related to known dicot LOX genes, with closest homologs found exclusively in other monocot species. ZmLOX12 is predominantly expressed in mesocotyls in which it is strongly induced in response to F. verticillioides infection. The Mutator transposon-insertional lox12-1 mutant is more susceptible to F. verticillioides colonization of mesocotyls, stalks, and kernels. The infected mutant kernels accumulate a significantly greater amount of the mycotoxin fumonisin. Reduced resistance to the pathogen is accompanied by diminished levels of the jasmonic acid (JA) precursor 12-oxo phytodienoic acid, JA-isoleucine, and expression of jasmonate-biosynthetic genes. Supporting the strong defense role of jasmonates, the JA-deficient opr7 opr8 double mutant displayed complete lack of immunity to F. verticillioides. Unexpectedly, the more susceptible lox12 mutant accumulated higher levels of kauralexins, suggesting that F. verticillioides is tolerant to this group of antimicrobial phytoalexins. This study demonstrates that this unique monocot-specific 9-LOX plays a key role in defense against F. verticillioides in diverse maize tissues and provides genetic evidence that JA is the major defense hormone against this pathogen.
authors.forename: Shawn A
authors.initials: SA
authors.lastname: Christensen
authors.forename: Andriy
authors.initials: A
authors.lastname: Nemchenko
authors.forename: Yong-Soon
authors.initials: YS
authors.lastname: Park
authors.forename: Eli
authors.initials: E
authors.lastname: Borrego
authors.forename: Pei-Cheng
authors.initials: PC
authors.lastname: Huang
authors.forename: Eric A
authors.initials: EA
authors.lastname: Schmelz
authors.forename: Susan
authors.initials: S
authors.lastname: Kunze
authors.forename: Ivo
authors.initials: I
authors.lastname: Feussner
authors.forename: Nasser
authors.initials: N
authors.lastname: Yalpani
authors.forename: Robert
authors.initials: R
authors.lastname: Meeley
authors.forename: Michael V
authors.initials: MV
authors.lastname: Kolomiets
mesh_terms: D000595:Amino Acid Sequence; D003517:Cyclopentanes / Q000378:metabolism*; D037341:Fumonisins / Q000378:metabolism; D005670:Fusarium / Q000472:pathogenicity / Q000502:physiology*; D008084:Lipoxygenase / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009928:Organ Specificity; D054883:Oxylipins / Q000378:metabolism*; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology; D010937:Plant Growth Regulators / Q000378:metabolism*; D057865:Plant Immunity; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D036226:Seedlings / Q000201:enzymology / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D012639:Seeds / Q000201:enzymology / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D003313:Zea mays / Q000201:enzymology* / Q000235:genetics / Q000276:immunology / Q000382:microbiology
chemical_list: D003517:Cyclopentanes; D037341:Fumonisins; D054883:Oxylipins; D010937:Plant Growth Regulators; D010940:Plant Proteins; C011006:jasmonic acid; D008084:Lipoxygenase