| Title: | Novel acidic sesquiterpenoids constitute a dominant class of pathogen-induced phytoalexins in maize |
| Author(s): | Huffaker A; Kaplan F; Vaughan MM; Dafoe NJ; Ni X; Rocca JR; Alborn HT; Teal PE; Schmelz EA; |
| Address: | "Center for Medical, Agricultural, and Veterinary Entomology, United States Department of Agriculture, Agricultural Research Service, Chemistry Research Unit, Gainesville, Florida 32608, USA. alisa.huffaker@ars.usda.gov" |
| ISSN/ISBN: | 1532-2548 (Electronic) 0032-0889 (Print) 0032-0889 (Linking) |
| 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 mug 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 beta-macrocarpene. Induced zealexin accumulation is preceded by increased expression of the genes encoding TERPENE SYNTHASE6 (TPS6) and TPS11, which catalyze beta-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: | "Acids/*metabolism Animals Cyclopentanes/metabolism Ethylenes/metabolism Feeding Behavior/drug effects Fungi/drug effects/growth & development/*physiology Gas Chromatography-Mass Spectrometry Gene Expression Regulation, Plant/drug effects Genes, Plant/gene;" |
| Notes: | "MedlineHuffaker, Alisa Kaplan, Fatma Vaughan, Martha M Dafoe, Nicole J Ni, Xinzhi Rocca, James R Alborn, Hans T Teal, Peter E A Schmelz, Eric A eng Research Support, U.S. Gov't, Non-P.H.S. 2011/06/22 Plant Physiol. 2011 Aug; 156(4):2082-97. doi: 10.1104/pp.111.179457. Epub 2011 Jun 20" |
