Maize pathogens suppress inducible phytoalexin production to thwart innate plant immunity

Authors: Christensen, Shawn; Sims, James; Huffaker, Alisa; Teal, Peter; Schmelz, Eric

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/25/2013
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Kauralexins and zealexins are newly described secondary metabolites in maize that serve as inducible chemical defenses against insects and pathogens. In contrast to the abundance of terpene volatiles in leaves, these non-volatile terpenoid phytoalexins are only mildly produced in response to insect herbivory; however, they are strongly induced by pathogen infection. While kauralexins and zealexins demonstrate antimicrobial properties, the aptitude of pathogenic fungi to manipulate their production remains unknown. We profiled phytoalexins and other common defense metabolites in nine commercial hybrid lines infected with three diverse pathogenic fungi. The necrotroph Cochliobolus heterostrophus induced a typical response with heightened levels of jasmonic acid, 12-oxo phytodienoic acid, salicylic acid, and phytoalexins including a novel terpenoid zealexin, designated zealexin A4. The hemi-biotroph Colletotrichum graminicola caused strong suppression of both kauralexins and zealexins. Interestingly, kauralexins were significantly active against C. graminicola as evidence by reduced growth when exposed to endogenous levels of occurring kauralexins A2/B2. Similarly, Fusarium graminearum infection repressed zealexin A4 production in infected maize tissues, and growth of F. graminearum was highly inhibited by zealexin A4 in vitro. These data indicate that maize pathogens manipulate phytoalexin production in attempt to avoid effective innate immunity responses.