Current position
Group Leader
Research interests
Determination of Photosynthetic capacity in plants
Collaborators: Susanne von Caemmerer and Dean Price
Improvements in crop yield during the twentieth century have
largely been achieved by manipulating factors other than optimising
photoassimilate production per unit leaf area. This has included
improved agronomic management practices, fertilizer application,
pest and disease control and breeding to alter the partitioning
of assimilates to the harvestable portion of the plant. Yet, recent
analyses of yield data from crops such as wheat has now indicated
that maximisation of photosynthesis and photoassimilate production
can contribute strongly to yield levels under both stressed and
non-stressed growth conditions
The aim of these studies is to learn more about the factors determining
the level of photosynthetic capacity within a leaf. We are investigating
limitations imposed by various metabolic enzymes as well as the
overall signal transduction networks that operate to influence
leaf and chloroplast photosynthetic development. The development
of molecular transgenic strategies for altering potential photosynthetic
rates is a long-term aim of this research with application to
improve such agronomic traits such as water-use efficiency and
nitrogen-use efficiency as well as improving yield under a range
of environmental conditions.
Research at present if focussed on both Arabidopsis and tobacco
investigating:
a. Identification of transcription regulators that affect photosynthetic
development, using whole-genome microarray technologies and characterisation
of the roles of candidate factors identified.
b. The potential for single gene overexpression to alter photosynthetic
properties, particularly in the photosynthetic carbon reduction
cycle and photorespiratory cycle.
The photosynthetic
CO2 concentrating mechanism in cyanobacteria: molecular components,
their diversity and evolution.
Collaborators: Dean Price
Cyanobacteria have evolved an extremely effective single-cell
CO2 concentrating mechanism (CCM). Recent molecular, biochemical
and physiological studies have significantly extended our knowledge
about the genes and protein components of this system and how
they operate to elevate CO2 around Rubisco during photosynthesis.
The CCM components include at least 4 modes of active inorganic
carbon uptake, including two bicarbonate transporters and two
CO2 uptake systems associated with the operation of specialised
NDH-1 complexes. All these uptake systems serve to accumulate
HCO3- in the cytosol of the cell, which is subsequently used by
the Rubisco-containing carboxysome protein micro-compartment within
the cell to elevate CO2 around Rubisco. The recent availability
of at least 9 cyanobacterial genomes has made it possible to begin
to undertake comparative genomics of the CCM in cyanobacteria.
Analyses have revealed a number of surprising findings. Firstly,
two groups of cyanobacteria are clearly identifiable characterised
by the possession of Form 1A or Form1B Rubisco (alpha and beta
cyanobacteria) and different carboxysome structures (alpha and
beta -carboxysomes). Secondly, the two HCO3- and CO2 transport
systems are distributed variably, with some cyanobacteria (Prochlorococcus
marinus species) appearing to lack CO2 uptake systems entirely.
Finally, there are multiple carbonic anhydrases in many cyanobacteria,
but surprisingly several cyanobacterial genomes appear to lack
any identifiable CA genes.
Our research is focussed on several areas of discovery:
1. The characterisation of the structure and function of alpha
and beta-carboxysomes
2. The identity and diversity of inorganic carbon transporters
in alpha and beta- cyanobacteria from marine and freshwater environments.
3. The inorganic carbon interconversion mechanisms in cyanobacteria
apparently lacking carbonic anhydrase genes.
Cyanobacterial species that can be genetically transformed and
which genome information is available for are central to our studies.
These include both alpha and beta-cyanobacteria. We are using
approaches that include detailed physiological analysis using
unique mass spectrometry gas exchange facilities; proteomic analysis
using MALDI-TOF and Q-TOF facilities. Gene expression is being
examined with real-time PCR approaches.
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Selected Publications
Osmond C.B., Daley P.F., Badger M.R., Luttge U. (1998) Chlorophyll
fluorescence quenching in leaves of Abutilon striatum Dicks. infected
with the gemini virus Arbutilon mosaic virus, observed with a
field-portable imaging system. Botanica Acta 111: 390-397.
Klughammer B., Sültemeyer D., Badger M.R., Price G.D. (1999).
The involvement of NAD(P)H dehydrogenase subunits, NdhD3 and NdhF3,
in high-affinity CO2 uptake in Synechococcus sp. PCC7002 gives
evidence for multiple NDH-1 complexes with specific roles in cyanobacteria.
Mol. Microbiol. 32: 1305-1315.
Flexas J., Badger M., Chow W.S., Medrano H., Osmond C.B. (1999)
Analysis of the relative increase in photosynthetic O2 uptake
when photosynthesis in grapevine leaves is inhibited following
low night temperatures and/or water stress. Plant Physiol. 121:
675-684.
Leggat W. Badger M.R., Yellowlees D. (1999) Photosynthesis and
the operation of a CO2 concentrating mechanism in the zooxanthellae
symbiont from the giant clam Tridacna. Plant Physiol. 121: 1247-1255.
Omata T., Price G.D., Badger M.R., Okamura M., Ogawa T. (1999)
Identification of an ABC-type bicarbonate transporter of the cyanobacterium
Synechococcus sp. Strain PCC7942 P.N.A.S. 96: 13571-13576.
Ruuska S.A., Andrews T.J., Badger M.R., Price G.D., von Caemmerer
S. (1999) The role of chloroplast electron transport and metabolites
modulating Rubisco activity in Tobacco: Insights from transgenic
plants with reduced amounts of cytochrome bf complex or glyceraldehyde
3-phosphate dehydrogenase. Plant Physiol. 122: 491-504.
Ruuska S.A., Badger M.R., Andrews T.J., von Caemmerer S. (2000)
Photosynthetic electron sinks in transgenic tobacco with reduced
amounts of Rubisco: Little evidence for significant Mehler reaction.
J. Expt Bot. 51: 357-368.
Eichelmann H., Price D., Badger M., Laisk A. (2000) Photosynthetic
parameters of leaves of wild type and Cyt b(6)/f deficient transgenic
tobacco studied by CO2 uptake and transmittance at 800 nm. Plant
Cell Physiol. 41: 432-439.
Ohkawa H., Price G. D., Badger M. R., Ogawa T. (2000) Mutation
of ndh genes leads to inhibition of CO2 uptake rather than HCO3-
uptake in Synechocystis sp strain PCC 6803. J Bacteriol. 182:
2591-2596.
Ruuska S. A., von Caemmerer S., Badger M. R., Andrews T. J.,
Price G. D., Robinson S. A. (2000) Xanthophyll cycle, light energy
dissipation and electron transport in transgenic tobacco with
reduced carbon assimilation capacity. Aust. J. Plant Physiol.
27: 289-300.
Maeda S., Price G.D., Badger M.R., Enomoto C., Omata T. (2000)
Bicarbonate binding activity of the cmpA protein of the cyanobacterium
Synechococcus PCC 7942 involved in active transport of bicarbonate.
J. Biol Chem. 275: 20551-20555.
Badger M.R., von Caemmerer S., Ruuska S., Nakano H. (2000) Electron
flow to oxygen in higher plants and algae: rates and control of
direct photoreduction (Mehler reaction) and rubisco oxygenase.
Phil. Trans. R. Soc. Lond. B 355: 1433-1446.
Sharkey T.D., Badger M.R., von Caemmerer S., Andrews T.J. (2001)
Increased heat sensitivity of photosynthesis in tobacco plants
with reduced Rubisco activase. Photosynth. Res. 67: 146-156.
Franklin L., Badger M.R. (2001) A comparison of photosynthetic
electron transport rates in macroalgae measured by pulse amplitude
chlorophyll fluorescence and mass spectrometry. J. Phycology 37:
756-767
Pike C.S., Grieve J., Badger M.R., Price G.D. (2001) Thermoptotective
properties of small heat shock proteins from rice, tomato, and
Synechocystis sp. PCC6803 overexpressed in, and isolated from,
Eschericia coli. Australian Journal of Plant Physiology 28: 1219-1229
Maeda S., Badger M.R., Price G.D. (2001) Novel gene products
associated with NdhD3/D4-containing NDH-1 complexes are involved
in photosynthetic CO2 hydration in the cyanobacterium, Synechococcus
sp. PCC7942. Molecular Microbiology 43: 425-435
Price G.D., Maeda S., Omata T., Badger M.R. (2002) Modes of
active inorganic carbon uptake in the cyanobacterium, Synechococcus
PCC7942. Functional Plant Biology 29: 131-149.
Leggat W., Marendy E., Baillie B., Whitney S., Ludwig M., Badger
M., Yellowlees D. (2002) Dinoflagellate symbioses: strategies
and adaptation for the acquisition of acquisition and fixation
of inorganic carbon. Functional Plant Biology 29: 309-322
Hanson D., Andrews T.J., Badger M.R. (2002) Variability of the
pyrenoid-based CO2-concentrating mechanism in hornworts (Anthocerotophyta).
Functional Plant Biology 29: 407-416
Badger M.R., Hanson D., Price G.D. (2002) Evolution and Diversity
of CO2 Concentrating Mechanisms in Cyanobacteria. Functional Plant
Biology 29: 161-173
Badger M.R., Price G.D. (2003) CO2 concentrating mechanisms
in cyanobacteria: molecular components, their diversity and evolution.
Journal of Experimental Botany 54: 609-622
Holtzapffel R.C., Finnegan P.M., Millar A.H., Badger M.R., Day
D.A. (2002) Mitochondrial protein expression in tomato fruit during
on-vine ripening and cold storage. Functional Plant Biology 29:
827-834
McGinn PJ, Price GD, Maleszka R, Badger MR (2003) Inorganic
carbon limitation and light control the expression of transcripts
related to the CO2-Concentrating Mechanism in the cyanobacterium
Synechocystis so. Strain PCC6803. Plant Physiology 132: 218-229.
Badger M.R. The roles of carbonic anhydrases in photosynthetic
CO2 concentrating mechanisms. Photosynthesis Research. In press
(September 2002)
Benschop J, Badger MR and Price GD (2003) Characterisation of
CO2 and HCO3- uptake in the cyanobacterium, Synechocystis sp.
PCC6803. Photosynthesis Research. (in Press October 2002).
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