Page 108 - PC2019 Program & Proceedings

PLANT CANADA 2019

Listing of Abstracts for the Speaker Program

S1. Transcriptome landscape of the early Brassica napus seed
Zeigler, D; D. Khan; J.L. Kalichuck; M.G. Becker; M.F. Belmonte
University of Manitoba

Brassica napus L. (canola) is one of the world’s most economically important oilseeds. Despite our
growing knowledge of Brassica genetics, we still know little about the genes and gene regulatory
networks underlying early seed development. In this work, we use laser microdissection coupled with
RNA sequencing to profile gene activity of both the maternal and filial subregions of the globular seed.
We find subregions of the chalazal end including the chalazal endosperm, chalazal proliferating tissue,
and chalazal seed coat, have unique transcriptome profiles associated with hormone biosynthesis and
polysaccharide metabolism. We confirm that the chalazal seed coat is uniquely enriched for sucrose
biosynthesis and transport, and that the chalazal endosperm may function as an important regulator of the
maternal region through brassinosteroid synthesis. The chalazal proliferating tissue, a poorly understood
subregion, was specifically enriched in transcripts associated with megasporogenesis and trehalose
biosynthesis, suggesting this ephemeral structure plays an important role in both sporophytic development
and carbon nutrient balance, respectively. Finally, compartmentalization of transcription factors and their
regulatory circuits has uncovered previously unknown roles for the chalazal pole in early seed
development.

Mark Belmonte (Mark.Belmonte@umanitoba.ca)

S2. Arabidopsis seed stored mRNAs are degraded constantly over aging time, as revealed by new
quantification methods
*1
1
2
Zhao, L. ; S. Wang ; Y-B. Fu ; H. Wang
1
1 University of Saskatchewan
2 Agriculture and Agri-Food Canada

How plant seeds age remains poorly understood and effective tools for monitoring seed aging are lacking.
Dry seeds contain various stored mRNAs which are believed to be required for protein synthesis during
early stages of seed germination. We reasoned that seed stored mRNAs would undergo degradation
during seed aging, based on the propensity of mRNAs to degrade. We performed RT-PCR and qPCR
analyses to study the changes in stored mRNA levels of Arabidopsis seeds. All stored mRNAs analyzed
were gradually degraded in both naturally and artificially aged seeds. The difference in Ct values between
aged and control seeds (ΔCt value) was highly correlated with the mRNA fragment size and seed aging
time. We derived mathematical equations for estimating the relative amount of undamaged stored
mRNAs and frequency of the breakdown at one nucleotide level for individual mRNAs. Our results
suggest that stored mRNAs were broken down randomly. The frequency of breaks per nucleotide per day,
which we named b value, remained fairly constant over aging time under the same aging conditions. Also,
we showed that the change in stored mRNA levels could serve as a more precise biomarker for seed aging
assessment compared to three existing methods. These findings have provided new insight on stored
mRNA degradation and seed aging in plants, and the methods developed will advance studies on stored
mRNAs.

Liang Zhao (liz704@usask.ca)

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