The control of starch degradation in Arabidopsis thaliana leaves at night

Feike, Doreen (2013) The control of starch degradation in Arabidopsis thaliana leaves at night. Doctoral thesis, University of East Anglia.

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Abstract

The aim of this work was to understand how Arabidopsis thaliana plants control starch
degradation at night. Starch is the major energy reserve in Arabidopsis. It is broken
down at night to maintain growth and metabolism of the plant, when photosynthesis is
not possible. The rate of starch degradation follows a linear pattern and is matched to
the length of the night period such that almost all starch is exhausted by dawn. The
mechanisms and the proteins involved in controlling starch degradation rates are largely
unknown.
With my work I wanted to identify components involved in the control of starch
degradation rates. Using a forward genetic screen, I discovered several mutants with
new starch degradation phenotypes. One of them was affected in the circadian clock
component EARLY FLOWERING 3 (ELF3). It degraded its starch slower than wildtype
plants and in a non-linear way. Two mutants degraded their starch at a much faster
rate than wild-type plants and exhausted their reserves before dawn. One of them lacks
a novel protein, which was named EXCESS STARCH TURNOVER 1 (EST1). This
protein is required for normal starch degradation rates, but its function is still unknown.
The second mutant is affected in BETA-AMYLASE 1 (BAM1) and produces aberrant
BAM1 protein containing a serine to asparagine amino acid substitution in position 132.
Faster starch degradation rates in this mutant depend on the presence of another protein
of the pathway, LIKE SEX FOUR 1 (LSF1). The data indicate that modulation of
BAM1 activity can strongly affect the rates of starch degradation, although starch is
degraded normally in absence of BAM1. In a second approach, I analysed which known
components of the starch degradation pathway are necessary for the adjustment of
starch degradation rates. I found that PHOSPHOGLUCAN WATER DIKINASE
(PWD) and BAM3 might play a role in adjusting starch degradation rates in response to
an unexpectedly early night.
In summary, in this thesis I introduce a novel protein necessary for normal starch
degradation rates in Arabidopsis leaves and provide insights into proteins and
mechanisms which might control starch degradation rates in response to an early night.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Mia Reeves
Date Deposited: 12 Mar 2014 09:35
Last Modified: 12 Mar 2014 09:35
URI: https://ueaeprints.uea.ac.uk/id/eprint/48101
DOI:

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