Inactivation of the lipoxygenase ZmLOX3 increases susceptibility of maize to Aspergillus spp.
Plant and fungal lipoxygenases (LOX) 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 LOX 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 wild-type (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 spp.) is in sharp contrast to results described herein for Aspergillus spp., suggesting that outcomes of LOX-governed host-pathogen interactions are pathogen-specific.
Gao
Xiquan
X
Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843-2132, USA.
Brodhagen
Marion
M
Isakeit
Tom
T
Brown
Sigal Horowitz
SH
Göbel
Cornelia
C
Betran
Javier
J
Feussner
Ivo
I
Keller
Nancy P
NP
Kolomiets
Michael V
MV
D000348:Aflatoxins / Q000096:biosynthesis; D001230:Aspergillus / Q000254:growth & development / Q000502:physiology*; D003517:Cyclopentanes / Q000032:analysis; D004198:Disease Susceptibility; D004789:Enzyme Activation; D005227:Fatty Acids / Q000032:analysis; D050356:Lipid Metabolism; D008084:Lipoxygenase / Q000235:genetics* / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D054883:Oxylipins / Q000032:analysis / Q000378:metabolism; D010641:Phenotype; D010935:Plant Diseases / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D013172:Spores, Fungal / Q000201:enzymology; D013241:Sterigmatocystin / Q000096:biosynthesis; D003313:Zea mays / Q000201:enzymology* / Q000382:microbiology*
D000348:Aflatoxins; D003517:Cyclopentanes; D005227:Fatty Acids; D054883:Oxylipins; D010940:Plant Proteins; D013241:Sterigmatocystin; C011006:jasmonic acid; D008084:Lipoxygenase