Abstract Detail

Molecular mechanisms of adaptation to host and environment

Ridenour, John [1], Smith, Jonathon [1], Hirsch, Robert [1], Horevaj, Peter [2], Kim, Hun [3], Sharma, Sandeep [1], Bluhm, Burton [1].

UBL1 of Fusarium verticillioides links the N-end rule pathway to extracellular sensing and plant pathogenesis.

Among eukaryotes, the N-end rule pathway is a conserved pathway for ubiquitin-dependent proteolysis.  Controlled protein degradation via the N-end rule pathway has been shown to mediate numerous cellular functions.  The N-end rule pathway depends on a UBR-Box/RING domain E3 ubiquitin ligase which recognizes N-end rule degrons of substrate proteins and mediates their ubiquitination and proteasomal degradation.  Despite the biological significance of the N-end rule pathway, there is very little information in filamentous fungi describing its involvement in environmental sensing or pathogenesis.  In the filamentous ascomycete Fusarium verticillioides, a ubiquitous kernel-rotting pathogen of maize, perception of starch is associated with the production of fumonisin mycotoxins.  Thus, insertional mutants were created and screened to identify genes involved in responding to extracellular starch.  In one mutant, the insertional cassette disrupted UBL1, a gene encoding a UBR-Box/RING domain E3 ubiquitin ligase.  Disruption of UBL1 in F. verticillioides (Δubl1) influenced conidiation, pigmentation, and amylolysis.  Disruption of UBL1 also impaired maize kernel colonization, however the ratio of fumonisin B₁ per unit growth was not significantly reduced.  The inability of a Dubl1 mutant to recognize a known N-end rule degron confirmed the involvement of UBL1 in the N-end rule pathway.  Additionally, Ubl1 physically interacted with two G protein α subunits of F. verticillioides, thus implicating UBL1 in G protein-mediated sensing of the external environment.  Furthermore, deletion of the UBL1 ortholog in F. graminearum led to impaired colonization of maize and wheat, thus indicating that UBL1 may have a conserved role in pathogenicity among Fusarium species.  This study provides the first linkage between the N-end rule pathway and fungal pathogenesis, and illustrates a new mechanism through which filamentous fungi respond to the external environment.

1 - University of Arkansas, Division of Agriculture, Department of Plant Pathology, Plant Sciences Building 217A, Fayetteville, AR, 72701, USA
2 - DuPont Pioneer, Maize Product Development, New Holland, PA, 17557, USA
3 - Seoul National University, Center for Fungal Pathogenesis, Seoul, 151-921, Republic of Korea

Keywords:
fumonisin
maize ear rot
amylolysis
E3 ubiquitin ligase
N-end rule pathway.

Presentation Type: Symposium or Colloquium Presentation
Session: SY5
Location: Room 103 AB/Kellogg Hotel and Conference Center
Date: Tuesday, June 10th, 2014
Time: 1:00 PM
Number: SY5001
Abstract ID:180
Candidate for Awards:None