Novel Acidic Sesquiterpenoids Constitute a Dominant Class of Pathogen-Induced Phytoalexins in Maize
Open Access
- 1 August 2011
- journal article
- Published by Oxford University Press (OUP) in Plant Physiology
- Vol. 156 (4), 2082-2097
- https://doi.org/10.1104/pp.111.179457
Abstract
Nonvolatile terpenoid phytoalexins occur throughout the plant kingdom, but until recently were not known constituents of chemical defense in maize (Zea mays). We describe a novel family of ubiquitous maize sesquiterpenoid phytoalexins, termed zealexins, which were discovered through characterization of Fusarium graminearum-induced responses. Zealexins accumulate to levels greater than 800 μg g−1 fresh weight in F. graminearum-infected tissue. Their production is also elicited by a wide variety of fungi, Ostrinia nubilalis herbivory, and the synergistic action of jasmonic acid and ethylene. Zealexins exhibit antifungal activity against numerous phytopathogenic fungi at physiologically relevant concentrations. Structural elucidation of four members of this complex family revealed that all are acidic sesquiterpenoids containing a hydrocarbon skeleton that resembles β-macrocarpene. Induced zealexin accumulation is preceded by increased expression of the genes encoding TERPENE SYNTHASE6 (TPS6) and TPS11, which catalyze β-macrocarpene production. Furthermore, zealexin accumulation displays direct positive relationships with the transcript levels of both genes. Microarray analysis of F. graminearum-infected tissue revealed that Tps6/Tps11 were among the most highly up-regulated genes, as was An2, an ent-copalyl diphosphate synthase associated with production of kauralexins. Transcript profiling suggests that zealexins cooccur with a number of antimicrobial proteins, including chitinases and pathogenesis-related proteins. In addition to zealexins, kauralexins and the benzoxazinoid 2-hydroxy-4,7-dimethoxy-1,4-benzoxazin-3-one-glucose (HDMBOA-glucose) were produced in fungal-infected tissue. HDMBOA-glucose accumulation occurred in both wild-type and benzoxazine-deficient1 (bx1) mutant lines, indicating that Bx1 gene activity is not required for HDMBOA biosynthesis. Together these results indicate an important cooperative role of terpenoid phytoalexins in maize biochemical defense.Keywords
This publication has 60 references indexed in Scilit:
- Identity, regulation, and activity of inducible diterpenoid phytoalexins in maizeProceedings of the National Academy of Sciences of the United States of America, 2011
- ZmPep1, an Ortholog of Arabidopsis Elicitor Peptide 1, Regulates Maize Innate Immunity and Enhances Disease ResistancePlant Physiology, 2011
- Restoring a maize root signal that attracts insect-killing nematodes to control a major pestProceedings of the National Academy of Sciences of the United States of America, 2009
- Phytohormone-based activity mapping of insect herbivore-produced elicitorsProceedings of the National Academy of Sciences of the United States of America, 2009
- Protonation of a Neutral (S)-β-Bisabolene Intermediate Is Involved in (S)-β-Macrocarpene Formation by the Maize Sesquiterpene Synthases TPS6 and TPS11Online Journal of Public Health Informatics, 2008
- Elucidation of the functional genomics of antioxidant-based inhibition of aflatoxin biosynthesisInternational Journal of Food Microbiology, 2008
- The products of a single maize sesquiterpene synthase form a volatile defense signal that attracts natural enemies of maize herbivoresProceedings of the National Academy of Sciences of the United States of America, 2006
- Recruitment of entomopathogenic nematodes by insect-damaged maize rootsNature, 2005
- Analysis of Relative Gene Expression Data Using Real-Time Quantitative PCR and the 2−ΔΔCT MethodMethods, 2001
- How caterpillar-damaged plants protect themselves by attracting parasitic wasps.Proceedings of the National Academy of Sciences of the United States of America, 1995