Page 169 - PC2019 Program & Proceedings

PLANT CANADA 2019

S123 Investigating the function of the APSES protein encoding gene apu2 (nlt1) during U. maydis
biotrophic growth
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Saville, B. ; E. Storfie ; M. Seegobin ; J. Meade ; P. Mukondiwa ; L. Branch ; M. Donaldson
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1 Trent University
2 University of Toronto
Ustilago maydis D.C. Corda is a model for investigating basidiomycete biotrophic pathogenesis. Recent
transcriptome analyses of its disease development, by Lanver et al (2018), revealed that the protein
encoded by UMAG_04778, which they called non-leaf tumor 1 (nlt1), had a controlling role in the third
wave of effector expression. We previously identified this gene in a cDNA subtraction library and termed
it APSES protein Ustilago maydis 2 (apu2) noting that it contained a previously unrecognized APSES
domain. This helix-loop-helix DNA binding domain is highly conserved in a group of fungal-specific
transcription factors described in the ascomycetes as being involved in the control of morphological
transitions. Previously in U. maydis, another APSES protein, Ust1, was shown to regulate dimorphism,
virulence, and sporulation. We discovered four other APSES proteins encoded in the U. maydis genome,
including apu2 which was the only family member with elevated transcript levels during pathogenic
development. Apu2 deletion did not inhibit plate mating or filamentous growth; however, it led to
decreased leaf tumor formation, and virulence as well as dramatically reduced teliospore formation during
solopathogenic haploid and dikaryon infections. Constitutive expression of apu2 led to plate growth and
pathogenesis phenotypes consistent with the hypothesis that Apu2 has a role in regulating morphological
transitions leading to teliospore development in U. maydis. This, as well as expression data on potential
downstream genes, will be presented.

Barry Saville (barrysaville@trentu.ca)

S124. Characterization of the Pyrenophora tritici-repentis-barley interaction
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Wei, B. ; M. Moscou ; K. Sato ; S. Strelkov ; Aboukhaddour, R.
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1 University of Alberta
2 The Sainsbury Laboratory
3 Institute of Plant Science and Resources, , 710-0046, Japan
4 AAFC
Tan spot caused by the necrotrophic fungus Pyrenophora tritici-repentis (Ptr) is a major foliar disease of
wheat worldwide. The fungus produces several necrotrophic effectors that trigger susceptibility in the
wheat host. While the Ptr-wheat interaction has been the focus of in-depth research over the last 40 years,
the nature of its interaction with various other gramineous hosts remain under-investigated. Here we
provide evidence for a specific interaction between barley and Ptr, describe the infection process and
highlight the genetics behind this interaction. A comprehensive genetic map composed of 381 SNP
markers was used to map the locus conditioning this specific interaction in a population of 94 double
haploid lines from a cross between Haruna Nijo and H602. Reaction to the race 5 isolate of the fungus, a
Ptr ToxB-producer, was evaluated at the seedling stage in a greenhouse. The lines segregated 1:1 for
susceptible: resistance phenotypes, indicating the involvement of a single locus. The locus was mapped to
the distal region of the short arm of chromosome 2H in barley. The region encompassing the locus
includes membrane receptor-like kinases (RLKs), intracellular nucleotide-binding, leucine-rich repeat
receptors (NLRs), and ankyrin-repeat proteins. The underlying gene will be identified using high
resolution mapping and transgenic complementation.

Reem Aboukhaddour (reem.aboukhaddour@canada.ca)

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