Abstract:
Key message 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.
Abstract 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 ‘‘offtarget’’
silencing of unintended genes in transformed plants
by aflR siRNAs. Overall, this work indicates that hostinduced
gene silencing has potential in developing aflatoxin-
resistant germplasm.
