Host-Induced Gene Silencing of the Aspergillus flavus O-methyl Transferase Gene Enhanced Maize Aflatoxin Resistance

Authors: OMOLEHIN, OLANIKE - Louisiana State University; Raruang, Yenjit; HU, DONGFANG - Louisiana State University; HAN, ZHU-QIANG - Guangxi Academy Of Agricultural Sciences; PROMYOU, SURASSAWADEE - Kasetsart University; Brown, Robert; Wei, Qijian; Rajasekaran, Kanniah; Cary, Jeffrey; WANG, KAN - Iowa State University; JEFFERS, DAN - Mississippi State University; CHEN, ZHIYUAN - Louisiana State University

Submitted to: Toxins
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/23/2024
Publication Date: 12/27/2024
Citation: Omolehin, O., Raruang, Y., Hu, D., Han, Z., Promyou, S., Brown, R.L., Wei, Q., Rajasekaran, K., Cary, J.W., Wang, K., Jeffers, D., Chen, Z. 2024. Host-Induced Gene Silencing of the Aspergillus flavus O-methyl Transferase Gene Enhanced Maize Aflatoxin Resistance. Toxins. 17(1). https://doi.org/10.3390/toxins17010008.
DOI: https://doi.org/10.3390/toxins17010008

Interpretive Summary: Contamination of corn with aflatoxin is a serious threat to the marketability of corn growers in the southern United States. They are also a serious threat to humans, livestock and pets. Making corn resistant is the most desirable way to reduce aflatoxin contamination. However, transferring resistant genes into elite breeding lines has met with limited success due to undesirable agronomic traits and incomplete resistance. We developed transgenic corn that reduced aflatoxin production through a new phenomenon known as Host Induced Gene Silencing (HIGS). We also transferred this gene into two elite inbred lines. These two elite lines also showed reduction of aflatoxin accumulation.

Technical Abstract: Maize is one of the major crops that are susceptible to Aspergillus flavus infection and subsequent aflatoxin contamination, which poses a serious health threat to human and domestic animals. Here, an RNA interference (RNAi) approach called Host-Induced Gene Silencing (HIGS) was employed to suppress the O-methyl transferase gene (omtA), a key gene involved in aflatoxin biosynthesis. An RNAi vector carrying part of the omtA gene was introduced into the B104 maize line. Among the six transformation events that were positive for containing the omtA transgene, OmtA-6, and OmtA-10, were self-pollinated from T1 to T4, and OmtA-7 and OmtA-12 to T6 generation. These four lines showed at least 81.3% reduction in aflatoxin accumulation at T3 generation under laboratory conditions. When screened under field conditions with artificial inoculation, OmtA-7 at T5 and T6 generations and OmtA 10 at T4 generation showed between 60% and 91% reduction in aflatoxin accumulation (P<0.02 to P<0.002). In order to develop commercial maize lines with enhanced aflatoxin resistance, the omtA transgene in OmtA-7 was introduced into two elite inbred lines through crossing and the resulting crosses also showed significantly lower aflatoxin accumulation compared to crosses with non-transgenic controls (P<0.04). In addition, high levels of omtA-specific small RNAs were only detected in the transgenic kernel tissues. These results demonstrate that suppression of omtA through HIGS can enhance maize resistance to aflatoxin contamination and this resistance can be transferred to elite background, providing a viable and practical approach to reduce aflatoxin contamination in maize.