Page 243 - PC2019 Program & Proceedings

PLANT CANADA 2019

P59. Genomic, chemical and functional analysis of adult leaf cuticle development in maize
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Molina, I. ; R. Bourgault ; P. Qiao ; S. Matschi ; M. Vasquez ; A. Sonntag ; C. Charlebois ; M.
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Mohammadi ; M. Gore ; M. Scanlon ; L. Smith
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1 Algoma University
2 Cornell University
3 University of California San Diego)

The cuticle is the outer physical barrier of plants and establishes a vital interaction interface with the
environment. This hydrophobic layer consists of the lipid polymer cutin embedded with and covered by
waxes, providing protection against environmental stresses including desiccation, UV radiation, and
pathogen attack. Thickness, structure, and chemical composition of the cuticle vary widely among plant
species, and even within a species, depend on organ identity, developmental stage, and growth conditions.
The functional contributions of the maize cuticle and its components to abiotic and biotic stress responses
have been rarely studied so far. Moreover, the cuticle biosynthesis and composition on the adult plant,
agronomically the most important growth phase, are largely unknown. In this study, we utilized the
expanding adult leaf as a model system to elucidate the timeline of maize cuticle development. We have
characterized the cuticle maturation along the leaf developmental gradient functionally (by measuring
cuticle permeability and resistance to water loss), biochemically (by performing a chemical analysis of
cutin and waxes), and genetically (by conducting epidermal-specific transcriptomic analysis). Cross-
referencing of the biochemical and transcriptomic data enabled the construction of gene regulatory and
co-expression networks, revealing a previously undescribed function for PHYTOCHROME-mediated
light signaling during cuticular wax deposition.

Isabel Molina (isabel.molina@algomau.ca)

P60. The role of starch in the development, physiology, and reproduction of Arabidopsis thaliana
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Costain, C. ; M. Emes; I. Tetlow
University of Guelph

Starch is an agronomically important polyglucan synthesized by plants as a means to store
photoassimilates as an osmotically inactive carbon store for subsequent use in metabolism and growth.
The synthesis of starch involves several enzymes working in concert, including starch branching enzyme
(SBE), responsible for cleaving alpha-(1,4)-bonds on pre-existing glucan chains and reattaching them to
the same or to neighbouring chains via alpha-(1,6)-linkages. SBE activity creates branch points and
contributes to starch’s semi-crystalline structure. Recently, SBEI and SBEIIb cloned from maize (Zea
mays) endosperm were constitutively expressed in a starchless, null line of Arabidopsis, lacking
endogenous SBEs. While both ZmSBEI and ZmSBEIIb were able to individually restore starch synthesis
in the null line, transformants exhibited altered starch metabolism. Here, we have re-transformed the null
line (sbe2.1 /sbe2.2 ) as well as Columbia (Col-0) with ZmSBEI and ZmSBEIIb under the control of a
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CaMV 35S promotor, and are in the process of characterizing these lines. Functional complementation of
Arabidopsis SBE null and Col-0 lines with maize SBEs represents a potential method to increase biomass
and production in agronomically important oilseed crops such as canola, as well as to shape the physical
characteristics of transient starch.

Cecily Costain (ccostain@uoguelph.ca)

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