Graduated PhD 2016
Environmental regulation of CO2 concentrating mechanisms in C4 grasses with different biochemical subtypes
Most terrestrial plants fix atmospheric CO2 into sugars via the C3 photosynthetic pathway. A smaller proportion of plants employ the C4 photosynthetic pathway which is distinguished by higher productivity and resource use efficiency. C4 photosynthesis is a series of anatomical and biochemical modifications that concentrates CO2 around the carboxylating enzyme Rubisco, thereby increasing photosynthetic efficiency in conditions promoting high rate of photorespiration. The C4 photosynthesis syndrome is divided into three major biochemical subtypes i.e. NADP-ME, NAD-ME and PCK. These plants consist of important food, feed and bio-fuel crops (e.g. maize, sorghum, sugarcane, millets), hence their global importance.
While differences in resource use efficiency between C3 and C4 plants are well documented and understood, little work has been done on elucidating the differences amongst the CO2 concentrating mechanism (CCM) of the three C4 sub-pathways (i.e., biochemical subtypes). The overall aim of this study is to elucidate the molecular and environmental factors regulating the efficiency of C4 photosynthesis by investigating the coordination of the CCM and its relationship with Rubisco catalysis in C4 leaves. In particular, the project will focus on the thermal responses of the in vivo and in vitro Rubisco kinetics in C4 grasses with different biochemical subtypes. The project will also unravel the various mechanisms underpinning the molecular and environmental coordination and plasticity of the CCMs in these C4 grasses.
Outcomes of this basic research will elucidate the impact of climate warming on C4 grasses. By providing fundamental knowledge of key regulatory mechanisms involved in the CCM of the various C4 subtypes, the project will support efforts aimed at bioengineering C4 photosynthetic traits into key C3 crops such as rice.
Sonawane BV, Sharwood RE, Whitney S, Ghannoum O, (2018) 'Shade compromises the photosynthetic efficiency of NADP-ME less than that of PEP-CK and NAD-ME C-4 grasses', Journal of Experimental Botany, vol.69, no.12, pp 3053-3068
Sharwood RE, Sonawane BV, Ghannoum O, Whitney SM, (2016) 'Improved analysis of C4 and C3 photosynthesis via refined in vitro assays of their carbon fixation biochemistry', Journal of Experimental Botany, vol.67, no.10, pp 3137-3148
Sharwood RE, Sonawane BV, Ghannoum O, (2014) 'Photosynthetic flexibility in maize exposed to salinity and shade', Journal of Experimental Botany, vol.65, no.13, pp 3715-3724 Special Issue: SI
Research Project Supervisors
A/Professor Oula Ghannoum, Dr Robert Sharwood (ANU), Dr Spencer Whitney (ANU)