Page 245 - PC2019 Program & Proceedings

PLANT CANADA 2019

P63. Investigating post-translational regulation of UDP-Glucose pyrophosphorylase in maize
endosperm
Butler, V.; I. Tetlow
University of Guelph

Cereals are the most cultivated crops in the world, and the starch they produce represents a major
component of caloric intake of the human diet. In cereal endosperms, starch synthesis requires the
formation of precursors produced from the cleavage of sucrose in the cytoplasm which are imported into
amyloplasts. Cytosolic UDP-glucose pyrophosphorylase (UGPase) plays an important role in producing
and providing the precursor for starch biosynthesis. UGPase catalyzes a reversible reaction that
contributes to sucrose and cell wall formation in the forward direction, and starch production in the
reverse direction. In endosperm tissue UGPase uses UDP-Glc and inorganic pyrophosphate (PPi) to make
Glc1P for starch biosynthesis, and Glc1P is in turn used by ADP-glucose pyrophosphorylase, the first
dedicated step in starch formation. UGPase is ubiquitous and is known to be active as a monomer,
showing reduced activity in an oligomeric form. While the role of UGPase in creating products used for
starch synthesis is well understood, mechanisms that regulate this enzyme in relation to starch synthesis
are unclear. A 14-3-3 binding motif at Ser-419, indicates the possible post-translational regulation of this
enzyme via protein phosphorylation and protein-protein interactions during starch synthesis. The
mechanisms of post-translational regulation for cereal endosperm UGPase in relation to starch
biosynthesis are being studied and are suspected to involve a combination of redox modulation, protein
phosphorylation, oligomer formation, and protein-protein interactions.

Victoria Butler (vbutler@uoguelph.ca)

P64. Investigating the functional evolution of plant shikimate kinase-like 1 (SKL1) in Marchantia
polymorpha
*
Lee, J. ; M. Kanaris; D. Christendat
University of Toronto

Chloroplasts house components of the photosynthetic machinery in addition to other critical metabolic
processes and are thus essential for all living plants. The biogenesis of chloroplasts is a highly active area
of study in plant biology. While there has been much progress in deciphering this complex process, many
aspects are still not well understood. One example is shikimate kinase-like 1 (SKL1), an ancient gene
duplicate of shikimate kinase that arose during the evolution of land plants between 400 and 500 million
years ago. The skl1-8 T-DNA insertional mutants of Arabidopsis thaliana exhibit an albino phenotype
with vesiculated plastids. One of our objectives is to investigate the evolutionary history of SKL1 through
studies of the bryophyte Marchantia polymorpha, the most ancient characterized species of land plant.
Our investigation has shown that this species possesses two highly similar homologs of SK with distinct
regions of dissimilarity. We have shown that one homolog is an active SK (MpSK), while the other lacks
such activity and is hypothesized to be a putative SKL1 (MpSKL1). We are currently engineering SK
activity into MpSKL1 through the reintroduction of specific functional domains in order to investigate the
functional diversification of MpSK into MpSKL1. We are also developing a MpSKL1 mutant using
CRISPR-Cas9 technology in order to confirm its function as an SKL1. Further work will provide
functional insights associated with SKL1.

Jonathan Lee (jonathans.lee@mail.utoronto.ca)

Page 243 of 339