| Summary: | The cuticle is a protective layer that coats the primary aerial surfaces of land plants,
and mediates plant interactions with the environment. It
is synthesized
by epidermal cells and
is composed of a cutin polyester matrix that is embedded and covered with cuticular waxes.
My overall interest in this thesis is to uncover the mechanisms in how cuticular wax
biosynthesis is regulated in developing stems of
Arabidopsis
thaliana.
Previous work
proposed that the
CER7 exoribonuclease degrades an
mRNA specifying a repressor of
CER3
transcription thereby activating cuticular wax biosynthesis via the alkane pathway.
In this thesis, I investigated the mechanisms of
CER7-mediated silencing of
CER3,
and how this contributes to regulating cuticular wax biosynthesis. Specifically, I wanted to
uncover the putative repressor of
CER3
and
to unravel the mechanism of CER7
mediated
regulation of wax production. To do this, I performed a genetic screen to isolate suppressors
of
cer7-1
which restore
cer7-related stem wax deficiency to wild-type wax levels. The
screen resulted in the isolation of components of the
RNA silencing machinery,
implicating
RNA silencing in the control of cuticular wax deposition during inflorescence stem
development in Arabidopsis.
Using a reverse genetics approach, I have also identified
AGO1
in this pathway.
Over
all, I demonstrate
that in the
wild
type, the
CER7
exoribonuclease degrades a
precursor of a small RNA that acts as a repressor of
CER3,
allowing for expression of
CER3,
and thus production of alkanes. However, in the
cer7
mutant, this small RNA is not
degraded and is used for the production of a small RNA silencing via a pathway.
The
generated small RNA silences
CER3, leading
to the wax deficient phenotype. === Science, Faculty of === Botany, Department of === Graduate
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