Chloroplasts

1
Chloroplasts compartment size organelle
population signalling, and the uncovering of
chloroplast master switches.
2
A tomato mutant with enhanced antioxidants (hp2)
- shows enhanced plastid development, and - is
defective in a repressors of photomorphogenesis
(LsDET1)
WT
hp2j
3
A cells plastid complement is dramatically
affected by loss of LsDET1
WT
hp2j
4
Loss of LsDET1 leads to at least a doubling in
plastid complement
5
Fruit-specific silencing of LsDET1 also leads to
increased cellular plastid compartment
wild type
2A11pDET1i
TFM7pDET1i
P119pDET1i
The increase can also be measured as
plastome/genome ratio
(Plants of Davuluri et al. 2005, Nature Biotech.
7 890-895)
6
Importantly, increased plastid compartment can be
achieved by combinations of increases in plastid
size and number
Exocarp
Plastid growth matters
7
Tight control of the total cellular plastid
complement has long been known in cereal leaves
(Pyke and Leech 1987, Planta 170 416-420)
Since plastid growth results from the expression
of nuclear genes, this implies plastid
compartment size retrograde signalling
8
Chloroplast biogenesis can be followed as part of
a whole transcriptome analysis of leaf initiation
in the light (distinguishing the shoot apex and
the cotyledons)
3dD
9
Indeed light upregulates specifically in the
shoot apex components of the plastid division
process, but this is unlikely to be the driving
force in chloroplast accumulation. Many other
processes occur.
10
Combined examination of biochemically-unrelated
chloroplast biogenesis genes reveals the
existence of modules of corregulated genes.