|Rajasekaran, Kanniah - Rajah|
|Wei, Qijian - Mei Mei|
Submitted to: International Plant Protection Congress
Publication Type: Abstract Only
Publication Acceptance Date: 2/20/2015
Publication Date: N/A
Technical Abstract: Introduction: Aflatoxigenic Aspergillus flavus is a frequent contaminant of agricultural commodities such as corn, peanut, tree nuts and cottonseed. Ingestion of foods, especially corn, contaminated with aflatoxins has been implicated in acute toxicoses while chronic, low-level exposure can lead to immune suppression and liver cancer in humans. RNA interference (RNAi) is a form of host-induced gene silencing (HIGS) that has evolved in most eukaryotes as a means of defense against viruses. RNAi silences targeted genes by degrading mRNA before it is translated into protein. RNAi has been used to increase disease resistance in plants susceptible to infection by pathogenic fungi. In these studies, fungal mRNAs destined for translation into proteins critical for growth and virulence were degraded by small interfering RNAs (siRNAs) produced by the plant RNAi machinery and subsequently translocated into the invading fungal pathogen. Objective: Develop and evaluate maize transformed with an RNAi vector targeting A. flavus alpha-amylase (amy) mRNAs that are critical for fungal growth and aflatoxin production. Materials and Methods: A binary RNAi vector expressing hairpin RNA (hpRNA) targeting the A. flavus amy gene was constructed and transformed into Hi-II maize via Agrobacterium. R0 seed from transgenic maize events was infected with a GFP-expressing A. flavus strain in an in vitro kernel screening assay (KSA). After 7 days infected seeds were analyzed for fungal growth, aflatoxin and amy gene expression. Fluorescence emanating from the fungus was used as a measure of fungal growth. Results: Preliminary results indicated significant reduction in both fungal growth and aflatoxin levels in several amy-RNAi transgenic lines compared to control. qRT-PCR of A. flavus amy gene expression correlated well with those amy-RNAi corn lines that demonstrated the greatest reductions in A. flavus growth and aflatoxin production. Conclusions: In vitro studies indicate that host induced gene silencing of A. flavus amy gene expression resulted in a significant inhibition of A. flavus growth and aflatoxin production in some of the transgenic maize lines.