Aflatoxin-Free Transgenic Maize Plants Via HIGS.

Aflatoxin is a toxic secondary compound produced by a fungal source that is responsible for massive global agricultural losses. Despite decades of control methods, currently there is still a global net loss of 16 million tons of maize due to aflatoxin contamination. Aflatoxin contamination in crops, and subsequently livestock, threatens greater agricultural development, food security and human health. Aflatoxin-contaminated food/feed can result in hepatotoxicity, liver cancer, kwashiorkor, Reye’s syndrome and stunt children’s growth. Here we demonstrate that host-induced gene silencing (HIGS), an RNAi suppression technology to produce small interfering RNA molecules in maize seeds targeted to fungal aflatoxin biosynthesis gene is effective to eliminate this toxin.  A hairpin RNAi structure was produced to target an aflatoxin biosynthetic gene in a kernel-specific manner in transgenic maize. Transgenic lines were challenged with Aspergillus-producing aflatoxin strains and assayed for toxin accumulation.  Although levels of toxin were detected in the control segregating null lines toxin accumulation was silenced in the challenged developing transgenic kernels. Presence of the inserted siRNA molecules homologous to the target fungal gene were detected to be expressed in the tested transgenic maize kernels by RT-PCR analysis. Transcript analysis of developing kernels from both transgenic RNAi kernels and null kernels showed no significant differences, indicating the gene expression profile of the transgenic kernels was unaffected by the RNAi trait. These results demonstrate that HIGS –induced pathway suppression can be an effective approach to mitigate the accumulation of aflatoxin in crops and provides an engineering strategy to improve food security.