title: Seed-Derived Ethylene Facilitates Colonization but Not Aflatoxin Production byAspergillus flavusin Maize.
abstract: Ethylene (ET) emitted by plant tissues has been broadly reported to play important roles in plant development, response to environmental stresses and defense against certain pathogens. Recent evidence obtained from usingin vitrofungal cultures exposed to ET suggested that exogenous ET may regulate the production of aflatoxin byAspergilli. However, the function of endogenous, seed-derived ET has not been explored. In this study, we found that the maize lipoxygenaselox3mutant, previously reported to be susceptible toAspergillusspp., emitted greater levels of ET uponA. flavusinfection, suggesting the potential involvement of endogenous ET in the susceptibility of maize toA. flavus. Supporting this idea, both colonization and conidiation ofA. flavuswere reduced in wild-type (WT) kernels treated with AgNO3, an ET synthesis inhibitor. There was no ET emission from non-viable kernels colonized byA. flavus, suggesting that living seed but not the fungus itself was the primary source of ET released upon infection withA. flavus. The kernels ofacs2andacs6, two ET biosynthetic mutants carryingMutatortransposons in the ACC synthase genes,ACS2andACS6, respectively, displayed enhanced seed colonization and conidiation, but not the levels of aflatoxin, upon infection withA. flavus. Surprisingly, bothacs2andacs6mutant kernels emitted greater levels of ET in response to infection byA. flavusas compared with WT seed. The increased ET in single mutants was found to be due to overexpression of functional ACS genes in response toA. flavusinfection. Collectively, these findings suggested that ET emitted by infected seed facilitates colonization byA. flavusbut not aflatoxin production.
authors.affiliation: State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Agriculture, Nanjing Agricultural University,Nanjing, China; Jiangsu Collaborative Innovation Center for Modern Crop Production, Nanjing Agricultural University,Nanjing, China.
authors.forename: Shi
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Plant Pathology and Microbiology, Texas A&M University, College Station,TX, USA; Division of Biotechnology, Chonbuk National University,Iksan, South Korea.
authors.forename: Yong-Soon
authors.initials: YS
authors.lastname: Park
authors.affiliation: State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Agriculture, Nanjing Agricultural University,Nanjing, China; Jiangsu Collaborative Innovation Center for Modern Crop Production, Nanjing Agricultural University,Nanjing, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX, USA.
authors.forename: Eli J
authors.initials: EJ
authors.lastname: Borrego
authors.affiliation: Jiangsu Collaborative Innovation Center for Modern Crop Production, Nanjing Agricultural University,Nanjing, China; Department of Plant Pathology and Microbiology, Texas A&M University, College Station,TX, USA.
authors.forename: Tom
authors.initials: T
authors.lastname: Isakeit
authors.affiliation: State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Agriculture, Nanjing Agricultural University,Nanjing, China; Jiangsu Collaborative Innovation Center for Modern Crop Production, Nanjing Agricultural University,Nanjing, China.
authors.forename: Xiquan
authors.initials: X
authors.lastname: Gao
authors.affiliation: Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX, USA.
authors.forename: Michael V
authors.initials: MV
authors.lastname: Kolomiets
keywords: Aspergillus flavus; aflatoxin; colonization; ethylene; maize