Maize terpene synthase 8 (ZmTPS8) contributes to a complex blend of fungal-elicited antibiotics

Authors: SALDIVAR, EVAN - University Of California, San Diego; DING, YEZHANG - Lawrence Berkeley National Laboratory; PORETSKY, ELLY - University Of California, San Diego; BIRD, SKYALR - University Of California, San Diego; Block, Anna; HUFFAKER, ALISA - University Of California, San Diego; SCHMELZ, ERIC - University Of California, San Diego

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2023
Publication Date: 3/1/2023
Citation: Saldivar, E.V., Ding, Y., Poretsky, E., Bird, S., Block, A.K., Huffaker, A., Schmelz, E.A. 2023. Maize terpene synthase 8 (ZmTPS8) contributes to a complex blend of fungal-elicited antibiotics. Plants. 12(5):1111. https://doi.org/10.3390/plants12051111.
DOI: https://doi.org/10.3390/plants12051111

Interpretive Summary: Corn is a major global agricultural food, feed and fuel, grain crop. Like many crops, its full production potential is hindered by fungal diseases that reduce yield and contaminate food and feed with harmful toxins. Certain varieties of corn have increased resistance to specific diseases and some of this resistance is due to the production of natural antimicrobial compounds by these varieties. Researchers at the University of California-San Diego in collaboration with USDA-ARS scientists in Gainesville Florida identified both an antimicrobial compound in corn that can reduce the growth of two fungal pathogens, and the corn genes responsible for its production. This information can allow breeders to select for corn varieties that produce this antimicrobial compound and enhance their resistance to fungal disease.

Technical Abstract: In maize (Zea mays), fungal-elicited immune responses include the accumulation terpene synthase (TPS) and cytochrome P450 monooxygenase (CYP) enzymes resulting in complex antibiotic arrays of sesquiterpenoids and diterpenoids, which include 'alpha/beta selinene derivatives, zealexins, kauralexins and dolabralexins. To uncover additional antibiotic families, we conducted metabolic profiling of elicited stem tissues in mapping populations including B73 x M162W Recombinant Inbred Lines (RILs) and the Goodman diversity panel. Five candidate sesquiterpenoids associated with a chromosome 1 locus spanning the location of ZmTPS27 and ZmTPS8. Heterologous enzyme co-expression studies of ZmTPS27 in Nicotiana benthamiana resulted in geraniol production while ZmTPS8 yielded 'alpha copaene, 'delta cadinene and sesquiterpene alcohols consistent with epi-cubebol, cubebol, copan-3-ol and copaborneol matching the association mapping efforts. ZmTPS8 is an established multiproduct alpha copaene synthase; however, ZmTPS8-derived sesquiterpene alcohols are rarely encountered in maize tissues. A Genome Wide Association Study further linked an unknown sesquiterpene acid to ZmTPS8 and combined ZmTPS8-ZmCYP71Z19 heterologous enzyme co-expression studies yielded the same product. To consider defensive roles for ZmTPS8, in vitro bioassays with cubebol demonstrated significant antifungal activity against both Fusarium graminearum and Aspergillus parasiticus. As a genetically variable qualitative biochemical trait, ZmTPS8 contributes to cocktail of terpenoid antibiotics present following complex interactions between wounding and fungal elicitation.