Nadine Töpfer - Environment-Coupled Models of Leaf Metabolism Capture Mechanisms of Crassulacean Acid Metabolism

November 2019

  • Date: Nov 6, 2019
  • Time: 02:00 PM - 03:30 PM (Local Time Germany)
  • Speaker: Nadine Töpfer
  • DEPARTMENT OF PLANT SCIENCES, UNIVERSITY OF OXFORD, UK
  • Location: Central Building
  • Room: Seminar Room
  • Host: Zoran Nikoloski

Increasing aridity threatens agricultural productivity not only in hot and dry climates but also in temperate regions where extreme weather conditions are becoming more frequent. Thus, developing water-use efficient crop varieties is of utmost importance to maintain food security. CAM photosynthesis is a water-saving mode of C-fixation in which CO2 uptake into the mesophyll cell and fixation by RuBisCO are temporarily separated. Implementing CAM photosynthesis into a C3 crop plant is a promising engineering target for two reasons, firstly, all enzymes involved in the CAM cycle are already present in C3 plants and secondly, some facultative CAM species can switch from C3 to CAM photosynthesis induced by a number of environmental factors.

In this presentation, I ask the question what are the metabolic and morphological limitations to implementing a water-saving CAM or CAM-like mechanism in a C3 leaf and what is the extent of the water-saving effect in different environments? This question is tackled by employing a time-resolved, large-scale metabolic leaf model which is c oupled to a gas-exchange model. The model thereby takes into account the two main determinants of water-loss through the stomata - temperature and relative humidity and is used to investigate emergent flux modes when water-saving constraints are applied in addition to high productivity.

As a result of this analysis, I will highlight three main findings. Firstly, the leaf’s vacuolar storage capacity is a major determinant of the extent of the CAM cycle and without engineering a higher vacuole to cytoplasm ratio it will be unlikely to introduce a full CAM cycle in a C3 leaf. Secondly, the reversibility of mitochondrial ICDH might contribute to initial carbon fixation at night-time. Thirdly, the water-saving effect of the CAM cycle strongly depends on the environment and the additional benefit of carbon fixation by ICDH can reach up to 4% percent less water usage for the environmental conditions tested.

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