Page 56 - PC2019 Program & Proceedings

PLANT CANADA 2019

PS3. Monday, July 8, morning session at 10:10 am

Dr. Leslie Sieburth

University of Utah, USA

Beyond transcription factors: A degrading story of gene
expression control

Abstract: Gene expression is a common component of many studies, and typically is quantified as mRNA
abundance. mRNA abundances, however, are controlled by both rates of synthesis (transcription) and rates of
decay, and yet roles of mRNA decay in regulating RNA abundances are largely unknown. To address this
problem, my lab uses genetic and genomic approaches to identify mRNA substrates of the decay pathways in
Arabidopsis. Mutants are used to link mRNA substrates with decay pathways, and our work focuses on
varicose (vcs), which is required for the mRNA decapping step that initiates 5'-->3' decay, and suppressor of
varicose (sov), which encodes a 3'-->5' exoribonuclease. The vcs mutant was initially identified because its
phenotype includes thick and misshapen veins, especially in cotyledons and leaves. By contrast, the sov
mutant has no obvious developmental defects. Genome-wide measurements of mRNA decay revealed that
mRNA decapping carries out a majority of the fast-decaying mRNAs, and the fast-decaying mRNAs include
those encoding transcription factors, components of signal transduction pathways, and genes annotated as
responding to stress or developmental signals. Analysis of mRNA substrates of sov, by contrast, led to
identification of an mRNA decay feedback pathway. In sov mutants, an over-compensating feedback
mechanism reorganizes patterns of mRNA decay, decay rates, and also affects transcription. The profoundly
altered gene expression dynamics in sov mutants maintains mRNA abundance at near wild-type levels. The
implications of mRNA decay rates and feedback pathways for regulation of gene expression will be discussed.
Bio:

Dr. Leslie Sieburth is a Professor and the Associate Director of the School of Biological Sciences at the University
of Utah. Dr. Sieburth's research uses genetic, genomic, and cell biological approaches to dissect fundamental
processes in plants. A major project focuses on gene expression, and regulatory roles of mRNA decay in
controlling mRNA abundance. Her lab was the first to identify VARICOSE (VCS), a scaffold protein that is essential
for functional assembly of the mRNA decapping complex, and also discovered SUPPRESSOR OF VARICOSE (SOV),
another cytoplasmic mRNA decay pathway. Recent studies using genome-wide approaches identified the mRNA
substrates of mRNA decapping and SOV, which also revealed overcompensating feedback pathways in mRNA
decay mutants. A second project examines root-to-shoot signaling, and identified the BYPASS1 gene as encoding
a negative regulator of a root-derived signaling molecule that causes strong physiological and developmental
responses in the shoot. This pathway appears to coordinate shoot physiology with perception of rhizosphere
conditions, and because BYPASS1-like genes are present in genomes of all land plants, this work suggests that
inter-organ communication mediated by BPS1 was vital as plants colonized land. Leslie began her independent
academic career in the Biology Department at McGill University.

https://faculty.utah.edu/u0143322-LESLIE_E_SIEBURTH/research/index.hml

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