ARS | Publication request: Maize terpene volatiles serve as precursors to an array of defensive phytoalexins following insect and pathogen attack

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 3, 2012
Publication Date: N/A

Technical Abstract: <p>Phytoalexins are inducible biochemicals that locally protect plant tissues against biotic attack. Due to their agronomic significance, maize and rice have been extensively investigated for their terpenoid-based defenses which include insect-inducible monoterpene and sesquiterpene volatiles. Rice also produces a complex array of non-volatile pathogen-inducible terpenoid phytoalexins; however, until recently analogous pathways in maize were unknown. We recently discovered the existence of a complex series of sesquiterpene and diterpene phytoalexins in maize stalks following attack by the European corn borer (Ostrinia nubilalis) and pathogenic fungi. The predominant acidic sesquiterpene and diterpene phytoalexins, termed zealexins and kauralexins, are likely derived from ß-macrocarpene and ent-kaur-15-ene, respectively. Following induction, the predicted volatile terpenoid precursors exist at relatively low levels compared to the oxygenated non-volatile end products. Induced zealexin and kauralexin accumulation is preceded by increased expression of the genes encoding TERPENE SYNTHASE 6 (TPS6), TPS11 and AN2, which catalyze the production of ß-macrocarpene and ent-copalyl diphosphate. Furthermore, phytoalexin accumulation displays direct positive relationships with the transcript levels of these genes. Combined, zealexins and kauralexins can reach concentrations approaching 1 mg/g FW in infected tissues and possess significant antifungal activity starting at 10 ug/g in liquid media. This past year 144,00 square miles of maize was planted in the US alone, contributing to the global harvest of over 850 million tons. While previously unnoticed, zealexins and kauralexins are likely to significantly contribute to maize disease resistance and ultimately productivity.