|MCAUSLANE, HEATHER - University Of Florida|
|ALLEN, LEON - Retired ARS Employee|
Submitted to: Plant Cell and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2014
Publication Date: 1/23/2015
Publication URL: http://handle.nal.usda.gov/10113/62950
Citation: Vaughan, M.M., Christensen, S., Schmelz, E.A., Huffaker, A., McAuslane, H.J., Alborn, H.T., Romero, M., Allen, L.H., Teal, P.E.A. 2015. Accumulation of terpenoid phytoalexins in maize roots is associated with drought tolerance. Plant, Cell and Environment. 38:2195–2207.
Interpretive Summary: Corn crop production, which is an essential part of the world’s grain supply, is limited by insect pests, pathogen diseases, and climatic conditions, such as drought. Recently two families of natural chemicals called zealexins and kauralexins were discovered in maize and found to function in defense against insects and pathogens. However, due to their only recent identification little is known about their function belowground in root tissues. We show that the concentration of zealexin and kauralexin compounds increases in maize roots exposed to beetle larvae (Diabrotica balteata) root feeding, root infection by the pathogen Fusarium verticillioides, drought stress, or salt stress. In a comparison with different corn varieties, plants with higher concentrations of these compounds tended to have higher root-to-shoot ratios which can be an indication of drought tolerance level. Additionally, we show that mutant corn plants unable to properly produce kauralexin compounds are more susceptible to drought and do not grow as well as control plants under the same water limitations. The results of this study should be of interest to a broad audience of plant pathologist and corn breeders particularly in the context of climate change which is expected to intensify issues of drought.
Technical Abstract: Maize (Zea mays) production, which is of global agro-economic importance, is largely limited by herbivore pests, pathogens, and environmental conditions, such as drought. Zealexins and kauralexins belong to two recently identified families of acidic terpenoid phytoalexins in maize that mediate defense against both pathogens and insect attack. However, little is known about their function in root tissues and potential role in overcoming abiotic stress. In this study we show that maize terpenoid phytoalexins also occur in root tissues and accumulate in response to both biotic and abiotic stress including, Diabrotica balteata herbivory, Fusarium verticillioides infection, drought, and high salinity. The quantity of drought induced phytoalexins is positively correlated with the root-to-shoot ratio of different maize varieties; and an2 mutant plants deficient in kauralexin production are more sensitive to drought. The induction of phytoalexins in response to drought is root-specific and does not influence phytoalexin levels aboveground; however, the accumulation of phytoalexins in one tissue may influence the induction capacity of other tissues.