title: Downregulation of transcription factor aflR in Aspergillus flavus confers reduction to aflatoxin accumulation in transgenic maize with alteration of host plant architecture.
abstract: We report success of host-induced gene silencing in downregulation of aflatoxin biosynthesis in Aspergillus flavus infecting maize transformed with a hairpin construct targeting transcription factor aflR. Infestation of crops by aflatoxin-producing fungi results in economic losses as well as negative human and animal health effects. Currently, the control strategies against aflatoxin accumulation are not effective to the small holder farming systems in Africa and this has led to widespread aflatoxin exposure especially in rural populations of sub-Saharan Africa that rely on maize as a staple food crop. A recent strategy called host-induced gene silencing holds great potential for developing aflatoxin-resistant plant germplasm for the African context where farmers are unable to make further investments other than access to the germplasm. We transformed maize with a hairpin construct targeting the aflatoxin biosynthesis transcription factor aflR. The developed transgenic maize were challenged with an aflatoxigenic Aspergillus flavus strain from Eastern Kenya, a region endemic to aflatoxin outbreaks. Our results indicated that aflR was downregulated in A. flavus colonizing transgenic maize. Further, maize kernels from transgenic plants accumulated significantly lower levels of aflatoxins (14-fold) than those from wild type plants. Interestingly, we observed that our silencing cassette caused stunting and reduced kernel placement in the transgenic maize. This could have been due to "off-target" silencing of unintended genes in transformed plants by aflR siRNAs. Overall, this work indicates that host-induced gene silencing has potential in developing aflatoxin-resistant germplasm.
authors.affiliation: Institute for Biotechnology Research, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya.
authors.forename: Joel Okoyo
authors.initials: JO
authors.lastname: Masanga
authors.forename: Jonathan Mutie
authors.initials: JM
authors.lastname: Matheka
authors.forename: Rasha Adam
authors.initials: RA
authors.lastname: Omer
authors.forename: Sheila Cecily
authors.initials: SC
authors.lastname: Ommeh
authors.forename: Ethel Oranga
authors.initials: EO
authors.lastname: Monda
authors.forename: Amos Emitati
authors.initials: AE
authors.lastname: Alakonya
mesh_terms: D000348:Aflatoxins / Q000032:analysis / Q000096:biosynthesis* / Q000378:metabolism; D001231:Aspergillus flavus / Q000378:metabolism / Q000502:physiology*; D015536:Down-Regulation; D015966:Gene Expression Regulation, Fungal / Q000235:genetics / Q000502:physiology; D020868:Gene Silencing / Q000502:physiology; D005800:Genes, Fungal / Q000235:genetics / Q000502:physiology; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000382:microbiology* / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D019076:Transgenes / Q000235:genetics / Q000502:physiology; D003313:Zea mays / Q000033:anatomy & histology / Q000737:chemistry / Q000235:genetics / Q000382:microbiology* / Q000502:physiology
chemical_list: D000348:Aflatoxins; D014157:Transcription Factors