Page 252 - Plant Canada 2024 Proceeding

PLANT CANADA 2024

immune response upon perceiving pathogen-secreted effectors. Therefore, accurate annotation of NLR
genes in B. napus is essential for understanding their functions and engineering elite cultivars in the
future. In this study, we selected the 'Westar' cultivar of B. napus for NLR re-annotation, which is widely
used in genetic mapping and transformation studies in Canada and elsewhere. A high-quality genome,
based on long-read sequencing, was selected for further analysis. Querying the annotated reference
protein sequences against the Pfam database indicated the presence of only 336 genes with domain
signatures associated with NLR proteins. To re-annotate the full NLR repertoire in B. napus cv. 'Westar,'
we applied the resistance gene enrichment sequencing (RenSeq) method. By combining RenSeq
mapping, the NLR-Annotator tool, and de novo gene prediction of problematic regions using AUGUSTUS,
we increased the number of annotated NLR genes from 336 to 774. Intriguingly, the majority of newly
identified NLR genes belong to unannotated or wrongly annotated regions in the reference genome.
Moreover, we compared the 'Westar' NLRome with those of other elite cultivars like 'ZS11' and 'Darmor-
bzh' to investigate the intraspecific diversity of NLR genes in terms of chromosome location, phylogenetic
relationships, integrated domains (IDs), and orthogroups (OGs) identification. We further applied RenSeq
and Oxford Nanopore whole-genome sequencing to annotate NLR genes in five clubroot-resistant B.
napus inbreed homozygous lines (IH1-IH5) with different resistance profiles. The results show 612, 600,
601, 601, and 597 NLR genes in these five lines, respectively. Taken altogether, the re-annotated NLR
genes in these B. napus susceptible and resistant lines provide a crucial resource for breeders and
researchers to improve disease-resistant gene discovery and evolutionary studies among Brassicaceae.

*[P98] SEED GERMINATION UNDER STRESS - MECHANISTIC INSIGHTS INTO THE EARLY LIFE
1,2
1,2
OF LONG-LIVED PLANTS. Michael Yankov , Oscar Felipe Nunez-Martinez , Stefan Heinen , and
2
Katharina Bräutigam . Cell and Systems Biology, University of Toronto, Toronto, ON, Canada, 2
1,2 1
Department of Biology, University of Toronto Mississauga, Mississauga, ON, Canada
Correspondence to: michael.yankov@mail.utoronto.ca

Seeds are critical for the propagation of individual plants, the persistence of plant populations and the
maintenance of terrestrial ecosystems. Seeds safely package the plant embryo for dispersal, and
successful germination is strongly influenced by environmental factors. With climate change and
increased anthropogenic activities such as mining or irrigation practices, soil salinity has increased
drastically and has removed thousands of hectares of land from use in agriculture and agroforestry in
Canada and worldwide. At the same time, little is known about the effect of salinity on seed germination in
many prominent forest trees.

Here, we systematically study the effect of increased salinity on seed germination in Populus, i.e. trees of
central importance for Canada’s forest and economy. Poplar seeds were exposed to increasing
concentrations of salt under controlled environmental conditions. Different ions and osmotic conditions
were studied. High salt concentrations can affect seeds and seedlings mechanistically through two
means: osmotic forces and toxic effects of ions. To discriminate between these two effects, salinity
treatments were compared to non-salt iso-osmotic controls. The effects on seed germination were tracked
over a period of ten days and threshold concentrations for seed germination were determined, which,
notably differed depending on the identity of the ions in the salts. We also introduced the criterion of
maximum harm that quantifies seedling damage post successful germination. In order to assess the
impacts of salinity on early plant development, germinated seedlings were classified into four distinct
developmental stages and monitored daily over the full period of the study. Finally, biomass production
was analyzed to assess plant growth during the early seedling establishment phase. Interestingly, it was
partially uncoupled from development, depending on the identity of the ions in the salt treatments.
Our findings contribute to the mechanistic understanding of germination and early plant development
under salt stress and can be critical for the selection of strategies, species, or genotypes in ecosystem
regeneration and land reclamation efforts.

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