Page 275 - Plant Canada 2024 Proceeding

PLANT CANADA 2024

[P142] TRANSCRIPTIONAL REGULATION OF ABSCISIC ACID AND GIBBERELLIN METABOLISM
GENES DURING SEED DEVELOPMENT IN BARLEY (HORDEUM VULGARE L.). Pham Anh Tuan,
Tran-Nguyen Nguyen, Parneet K. Toora, and Belay T. Ayele. Department of Plant Science, University of
Manitoba, Winnipeg, MB, Canada
Correspondence to: belay.ayele@umanitoba.ca

Seed development is a complex physiological process which is partly regulated by abscisic acid (ABA)
and gibberellins (GAs). However, regulation of the metabolism of these hormones during barley seed
development is not well understood. This study investigated spatiotemporal changes in the expression
patterns of ABA and GA metabolism genes and endogenous levels during development of barley seeds.
Elevated levels of ABA and GA were observed in both embryo and endosperm tissues during the
early/main seed filling (SF) phase, suggesting the role of ABA and GA in embryo development, organ
expansion and accumulation of storage reserves. During transition from early to physiological maturity
(PM) phase, endospermic ABA level showed an increase and this is associated with expression patterns
of NCEDs and CYP707A2 genes while GA level showed a decrease and this is regulated by
downregulation of GA3ox2 and upregulation of GA2ox genes during the same period. Low levels of ABA
and no GAs were detected in the endosperm during post-PM. The PM stage, which is known to exhibit
high level of dormancy, is associated a peak in embryonic ABA level that is regulated mainly by the
expression of NCED genes, and a low level of GA, which is controlled by GA20ox, GA3ox and GA2ox
genes. The embryo during post-PM phase is characterized by the detection of certain amount of ABA but
not GA, suggesting the role of ABA in desiccation tolerance. Our study indicates that spatiotemporal
changes in ABA and GA levels, which are mediated by transcriptional regulation of specific genes
involved in their respective metabolic pathways, regulate physiological processes during barley seed
development.

[P143] BACILLUS CEREUS IN CANADIAN GRAIN: MICROBIAL COMMUNITY PROFILING. Niradha
Withana Gamage , Tehreem Ashfaq , Tiffany Chin , Janice Bamforth , and Sean Walkowiak . Grain
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Research Laboratory, Canadian Grain Commission, Canada
Correspondence to: sean.walkowiak@grainscanada.gc.ca

Grain and grain products can become contaminated with microorganisms derived from various sources
including plants, insects, water, soil, fertilizers, and animal feces. Bacteria such as Bacillus cereus can
survive for extended periods of time in these low moisture foods. Bacillus cereus is a facultative
anaerobic, Gram-positive, rod-shaped, spore forming bacterium widely distributed in nature. However,
these bacteria have demonstrated a crucial role as beneficial bacteria in plants while some have been
reported as harmful pathogens causing food poisoning in consumers. Studies showed that some species
of B. cereus have influenced plant growth and crop yield by acting as plant growth promoting bacteria
(PGPB) and by inhibiting broad range of plant pathogens and insect pests. Adversely, B. cereus has
gained special attention worldwide as a foodborne pathogen due to their potential of producing toxins
causing gastrointestinal illnesses. The purpose of this study was to investigate the B. cereus community
profile associated with raw grain samples received at the Canadian Grain Commission. We screened (n =
508) wheat samples received in 2018 and (n = 636) of wheat and flax samples received in 2017 and
analysed them using molecular techniques. Grain bacteria were isolated by enriching samples as per a
modified protocol (Health Canada MFLP-52). Pure colonies were isolated and confirmed using
Chromogenic culture media and their DNA was tested with real-time PCR and by Illumina sequencing.
The overall B.cereus isolation rate in the current study was 56.3% in 2018 and 85.2% in 2017.
Comparative genomics of 109 presumptive B. cereus isolates divided most of them into two genetically
distinct groups. Additionally, molecular characterization revealed that the B.cereus population in grain
was composed of diverse genetic elements including: enterotoxin genes causing gastrointestinal illnesses
(nheA and hbID), antimicrobial resistance genes and genes involved in the production of insecticidal
proteins (Cry). Our study investigated the composition of B. cereus in Canadian grain in two different
harvest years and the results shows the value of surveillance of bacteria naturally occurring in raw grain.
Ongoing research is being conducted to screen B. cereus isolates associated with grain that may pose a
risk for consumers in term of food safety and also to investigate the possible B. cereus candidates as
beneficial biocontrol agents or PGPB in plants.

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