Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2022
Publication Date: 8/12/2022
Citation: Tang, H.V., Berryman, D.L., Mendoza, J.S., Yactayo Chang, J.P., Li, Q., Christensen, S.A., Hunter III, C.T., Best, N.B., Soubeyrand, E., Akhtar, T., Basset, G.J., Block, A.K. 2022. Dedicated farnesyl diphosphate synthases circumvent isoprenoid-derived growth-defense tradeoffs in Zea mays. Plant Journal. https://doi.org/10.1111/tpj.15941.
DOI: https://doi.org/10.1111/tpj.15941

Interpretive Summary: Crops use a natural form of chemical warfare to protect themselves against insect and microbial pests. The ability of plants to make such defensive compounds has arisen via duplication and evolution of the synthesis pathways plants use to make chemicals needed for growth. As the plants need common building blocks to make chemicals needed for defense and growth, they require mechanisms to maintain growth while defending themselves from attack. ARS scientists at the Center for Medical, Agricultural, and Veterinary Entomology in Gainesville FL, in collaboration with researchers from the University of Florida uncovered one such mechanism corn uses to achieve this growth-defense balance. These findings can aid in the production of crops with improved natural chemical defenses and reduce the dependence of agriculture on synthetic pesticides.

Technical Abstract: Zea mays (maize) produces inducible anti-microbial phytoalexins to combat invading pathogens. A subset of these phytoalexins are sesquiterpenoid zealexins, produced in microgram per gram quantities from farnesyl diphosphate. As farnesyl diphosphate is also a precursor for many compounds essential for plant growth, the question arises as to how Z. mays produces high levels of zealexins without negatively affecting vital plant systems. The production of specific pools of farnesyl diphosphate for zealexin synthesis could bypass this problem. To examine this possibility, we made CRISPR/Cas9 knock outs of each of the three farnesyl diphosphate synthases (FPS) in Z. mays and examined the resultant impacts on different farnesyl diphosphate-derived metabolites. We found that FPS3 (GRMZM2G098569) produced farnesyl diphosphate for zealexins, while FPS1 (GRMZM2G168681) provided farnesyl diphosphate for the vital respiratory co-factor ubiquinone. Indeed, fps1 mutants had strong developmental phenotypes such as reduced stature, development of chlorosis and decreased pollen fitness. However, compounds such as sterols and herbivore induced sesquiterpene volatiles were less dependent on specific FPS isoforms. These results suggest Z. mays evolved dedicated FPSs to produce zealexins while protecting vital compound production, thus circumventing negative growth-defense tradeoffs.