Page 195 - PC2019 Program & Proceedings

PLANT CANADA 2019

S175. Transcription regulatory map reveals important transcription factors regulating late blight
resistance, leading to a higher accumulation of resistance related metabolites
1
2
*1
Joshi, S. ; R.S. Heikham ; A. Gagnon ; A. Kushalappa
1
1 McGill University
2 Progest 2001 Inc.
Late blight of potato caused by Phytophthora infestans causes up to 40% yield loss worldwide.
Resistance to late blight is either qualitative or quantitative. Even though quantitative resistance is
durable, its regulation is not well deciphered, which limits its applications. Based on RNA seq and semi-
targeted metabolomics we identified several Resistance Related Induced (RRI) genes and metabolites
upon pathogen inoculation, in resistant genotype (Libertas) compared to susceptible genotype
(AG704.10). A total of 281 resistance related constitutive (RRC) and 160 RRI metabolites were detected,
which belonged to different chemical groups. RNAseq and de novo assembly identified 611 RRI genes
which were further categorized based on their biological functions. Promoter sequences of these RRI
genes were identified, using in house script, which was used for transcription factor (TF) enrichment
study to identify regulatory transcription factors. 134 transcription factors (p <0.05) were found to have
binding sites in the promoters of RRI genes. Among these, bHLH66, MYB61, NAC56, WRKY51 and MYB
like HHO2 transcription factors were upregulated after pathogen inoculation. These TFs were further
mapped to downstream genes, and these were mainly the resistance related metabolite biosynthetic genes.
The RRI genes identified here can be exploited to enhance disease resistance in susceptible cultivars,
following further characterization of their resistance functions.

Sripad Joshi (sripad.joshi@mail.mcgill.ca)

S176. Tuber-specific expression of a heterologous host defense peptide reduces post-harvest
diseases in potato
Yevtushenko, D.
University of Lethbridge

Development of control strategies to fight plant diseases effectively and with minimal impact on the
environment is one of the greatest challenges for food security in this century. In the present study,
evaluation of the spatiotemporal activities of various plant promoters in transgenic hosts using the GUS
reporter gene system revealed that the PmBiPPro1 promoter of the luminal binding protein (BiP) from
Douglas-fir exhibited organ-specific, wound-inducible and developmental patterns of activity, with
particularly high transcriptional activity in potato tubers. The latter suggests that this promoter likely
contains important cis element(s) that interact with tuber-specific transcription factors required for
promoter activation in the storage organs. The organ-specific activity of the PmBiPPro1 promoter was
examined for targeted expression of MsrA2 peptide in potato tubers. MsrA2 is a small membrane-active
host defense peptide, containing the full-length amino acid sequence of naturally occurring dermaseptin
B1 (31 residues) and exhibiting high antimicrobial activity against phytopathogenic fungi and bacteria.
The nucleotide sequence encoding MsrA2 was transcriptionally fused to the PmBiPPro1 promoter, and
introduced into potato via Agrobacterium-mediated transformation. Western blot analysis showed high
level of MsrA2 accumulation in tubers of transgenic plants. Moreover, in vitro bioassays revealed that the
expression level of the MsrA2 peptide in tubers was sufficient to confer resistance to bacterial soft rot and
Fusarium dry rot, two major potato diseases causing post-harvest losses of potatoes.

Dmytro Yevtushenko (dmytro.yevtushenko@uleth.ca)

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