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Host induced gene silencing targeting aflM reduced aflatoxin contamination in transgenic corn

Yenjit Raruang: Louisiana State University Agricultural Center

<div>Reducing <em>Aspergillus flavus </em>infection and subsequent aflatoxin contamination in corn through biocontrol and developing resistant cultivars has so far met with limited success. In the present study, a novel host induced gene silencing (HIGS) strategy was employed to suppress the expression of <em>aflM</em>, an <em>A. flavus </em>gene encoding versicolorin, a key enzyme involved in the aflatoxin biosynthesis. An RNAi vector containing a portion of the <em>aflM</em> gene was constructed and introduced into B104 immature embryos through <em>Agrobacterium </em>transformation. Twenty-three transgenic plants were produced from seven independent transformation events. Six of seven transformation events were confirmed by PCR to have the <em>aflM</em> gene. The T<sub>2</sub> generation kernels containing the transgene from two events out of four examined had less aflatoxin (p=0.01 and p=0.08) than those without the transgene. Field-inoculated homozygous T<sub>3</sub> transgenic kernels also revealed lower aflatoxin (p=0.02) than kernels from the null or B104 controls. Similar result was observed when the harvested T<sub>3</sub> homozygous transgenic kernels were evaluated under kernel screening assay conditions (p=0.008). In addition, significantly higher levels of <em>aflM</em> gene-specific small RNAs were detected in the transgenic leaf tissue, indicating that the enhanced aflatoxin resistance in the homozygous transgenic kernels is likely due to suppression of <em>aflM </em>expression through HIGS.</div>