Potential role of a maize metallothionein gene in pest resistance

Authors: Dowd, Patrick; Naumann, Todd; Johnson, Eric

Submitted to: Plant Gene
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2023
Publication Date: 2/9/2023
Citation: Dowd, P.F., Naumann, T.A., Johnson, E.T. 2023. Potential role of a maize metallothionein gene in pest resistance. Plant Gene. 34. Article 100409. https://doi.org/10.1016/j.plgene.2023.100409.
DOI: https://doi.org/10.1016/j.plgene.2023.100409

Interpretive Summary: Corn is one of the most important crops in the US and around the world. Corn quality and production is lessened by both insect and fungal pests. In this work ARS scientists in Peoria, Illinois, identified a corn gene that is often damaged in corn varieties but is functional in a pest resistant one. This gene encodes a protein called MET. MET was found to inhibit growth of both insects and fungi and a biochemical explanation for this biological activity was identified. Ensuring that corn varieties have a functional MET-encoding gene will reduce pest damage, benefiting farmers and consumers.

Technical Abstract: Maize is grown worldwide and much of the world depends on its production, which is lessened by insect and fungal pests. Many maize genes with the potential to improve pest resistance exist in non-functional forms in modern inbreds but are functional in those that show improved resistance. One such gene, encoding a metallothionein protein, was located from a resistance locus of maize inbred GE440, which shows resistance to Fusarium ssp. pathogens. The identified gene, encoding zmMET2, is damaged in many maize inbreds, including the model inbred B73. When expressed in maize callus, zmMET2 significantly increased resistance to F. proliferatum and F. verticillioides with less effectiveness against F. graminearum. Callus expressing zmMET2 also retarded growth of two classes of insect pests, fall armyworms and corn earworms. Recombinant zmMET2 was purified from bacteria. The purified protein was found to bind zinc, copper, and nickel and scavenged reactive oxygen species in vitro, which gives a possible mechanism for its antiinsect and antifungal activities. In bioassays, the purified protein retarded growth of fall armyworms but did not show activity against fungi, suggesting that the antifungal activity observed in callus tissue is dependent on other plant factors. The inclusion of the identified gene in new plant varieties should increase resistance to both insects and fungi.