Skip to main content
ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Cereal Crops Research » Research » Publications at this Location » Publication #315249

Title: A ToxA-like protein from Cochliobolus heterostrophus induces light-dependent leaf necrosis with host selectivity on maize

Author
item Lu, Shunwen
item Edwards, Michael

Submitted to: American Phytopathological Society
Publication Type: Abstract Only
Publication Acceptance Date: 5/8/2015
Publication Date: 8/1/2015
Citation: Lu, S., Edwards, M.C. 2015. A ToxA-like protein from Cochliobolus heterostrophus induces light-dependent leaf necrosis with host selectivity on maize. American Phytopathological Society. http://www.apsnet.org/meetings/Documents/2015_meeting_abstracts/aps2015abP184.htm.

Interpretive Summary:

Technical Abstract: ToxA, the first discovered fungal proteinaceous host-selective toxin (HST), was originally identified from Pyrenophora tritici-repentis (Ptr), and its homologues have not been identified from any other ascomycetes except Parastagonospora nodorum. Here we report the identification of a ToxA-like protein from the maize pathogen Cochliobolus heterostrophus (Ch). ChToxA is encoded by a 535-bp open reading frame featuring a ToxA-specific intron with unusual splicing sites at conserved positions relative to PtrToxA. The protein shows 64% similarity to Ptr ToxA and is predicted to adopt a ToxA-like three-dimensional structure, although lacking the arginyl-glycyl-aspartic acid (RGD) motif. Reverse-transcriptase PCR revealed that the ChToxA gene is expressed at low levels in fungal cultures, but is up-regulated during fungal pathogenesis. Plant assays indicated that the recombinant ChToxA protein induces light-dependent leaf necrosis in a host-selective manner on maize inbred lines. Gene knockout experiments confirmed that chtoxa null mutants sustain reduced virulence on specific ToxA-sensitive maize lines. Database searches identified potential ChToxA homologues in other plant-pathogenic ascomycetes. These results suggest that C. heterostrophus is capable of producing proteinaceous HSTs in addition to virulence-related secondary metabolites. Further studies on ChToxA may provide new insights into effector evolution in host-pathogen interactions.