Page 168 - PC2019 Program & Proceedings

PLANT CANADA 2019

S121. Transcriptomic response of multiple Brassica species to Sclerotinia sclerotiorum infection
de Jong, G.; K. Adams
University of British Columbia

Whole-genome duplication (WGD; polyploidy) events have played an extensive role in the evolution of
flowering plants. The sudden doubling of genetic material can expedite rapid novel changes to polyploid
transcriptomes. For example, polyploids formed via an interspecific hybridization of closely related
species, or allopolyploids, can exhibit expression patterns inconsistent with their parental species.
Consequently, allopolyploidy could have profound effects on the stress responses of these hybrids;
however, the extent to which the transcriptomic shock that follows WGD events plays a role in a biotic
stress response remains a nascent topic in polyploidy research. To investigate the interplay between
polyploid gene expression and biotic stress response, Brassica napus, Brassica oleracea, Brassica rapa,
and a synthetic Brassica napus (formed directly from the aforementioned parental species of B. napus)
were subjected to the economically devastating fungus Sclerotinia sclerotiorum. RNA-Seq analysis of
these pathosystems revealed wide-spread transcriptomic changes involving both constitutive gene
expression and alternative splicing. Cross-species comparisons showed a concerted response between all
assayed Brassica species characterized by the up-regulation of jasmonic acid signalling pathways, cell-
wall defense genes, chitinases, and pathogen responsive genes. Subgenome comparisons also showed
considerable non-parental gene expression patterns in the synthetic Brassica napus, in addition to a C-
subgenome expression bias, suggesting transcriptome reprogramming occurs relatively quickly following
polyploidization.

Grant de Jong (dejong.grant@gmail.com)

S122. Lectin genes in Brassica napus enhance resistance to the fungal pathogen Sclerotinia
sclerotiorum
Buchwaldt, L.; D. Hegedus; D. Bekkaoui; J. Durkin; J. Nettleton; E. Dzanaovic
Agriculture and Agri-Food Canada

Lectins are known to contribute to defense against fungi, virus, bacteria and insect pests. We have shown
that certain lectin genes are up-regulated in canola (Brassica napus) after inoculation with the fungal
pathogen Sclerotinia sclerotiorum. To investigate the effectiveness of lectin genes, a single allele of
curculin, concanavalin and hevein, were cloned from the partially resistant cultivar Zhongyou 821 and
each inserted in a susceptible line, DH12075, under the constitutive gene promoter, CaMV35S, using
Agrobacterium-meditated transformation. Subsequently, five transformed lines showed 50-80% reduction
in disease severity. The three lectins have a signal peptide (SP) that directs the protein into vacuoles
destined for the cell’s secretory system, and the remaining protein contains one or more carbohydrate
recognition domains (CRD) with different substrate specificities. Both curculin and concanavalin CRDs
have mannose specificity, while hevein has chitin specificity. Since both mannose and chitin are
constituents of fungal cell walls they are targeted by these CRD. In Arabidopsis these lectin genes are
induced by fungal pathogens or chitin treatment, and their proteins are prominent in both apoplast and
xylem. The lectin genes cloned from Zhongyou 821 harbour amino acid substitutions in either CRD and
SP domains, which could account for enhanced vacuolar secretion or higher affinity for fungal
carbohydrate moieties leading to enhanced resistance to S. sclerotiorum. The genes or transformed lines
might be used in future canola breeding.

Lone Buchwaldt (Lone.Buchwaldt@canada.ca)

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