JXB celebrates C4

29 April 2017 - By: Jonathan Ingram & Christine Raines

JXB celebrates C4

JXB Celebrates C4
Pioneers of C4 photosynthesis Roger Slack (left), Hal Hatch (right) and Hilary Warren (centre, Hatch’s first PhD student) in 2016, 50 years after the first published characterization of the C4 photosynthetic pathway by Hatch and Slack. Photo: Sharyn Wragg, Research School of Biology, ANU/ CoE for Translational Photosynthesis.

By Jonathan Ingram & Christine Raines, Senior Commissioning Editor and Editor-in-Chief

Effects of reduced carbonic anhydrase activity on CO2 assimilation rates in Setaria viridis: a transgenic analysis.

Osborn HL, Alonso-Cantabrana H, Sharwood RE, Covshoff S, Evans JR, Furbank RT, von Caemmerer S ( 2017)

Journal of Experimental Botany 68, 299–310 https://doi.org/10.1093/jxb/erw357

Loss of photosynthetic efficiency in the shade. An Achilles heel for the dense modern stands of our most productive C4 crops?

Pignon CP, Jaiswal D, McGrath JM, Long SP (2017)

Journal of Experimental Botany 68, 335–345  https://doi.org/10.1093/jxb/erw456

Metabolite pools and carbon flow during C4 photosynthesis in maize: 13CO2 labeling kinetics and cell type fractionation.

Arrivault S, Obata T, Szecówka M, Mengin V, Guenther M, Hoehne M, Fernie AR, Stitt M (2017)

Journal of Experimental Botany 68, 283–298 https://doi.org/10.1093/jxb/erw414

Fifty years after the discovery of C4 metabolism the research field is resurgent, with the aim to introduce this pathway into C3 rice. A JXB special issue celebrates both the discovery and recent achievements in elucidating the evolution and development of the C4 syndrome. Three papers reveal limitations to C4 photosynthesis under different environmental conditions. Osborn et al. looked at carbonic anhydrase, which catalyses the hydration of atmospheric carbon dioxide for PEP carboxylase in the first step of the pathway. Using transgenic plants with reduced carbonic anhydrase activity, they found that at low intercellular CO2 partial pressure, as can occur under drought, mesophyll conductance may be a greater limitation even than activity of the enzyme. Water availability is just one of many potential limitations to plant growth, and these can be very different in agriculture. Pignon et al. found that shade from neighbouring plants is a significant issue in C4 crops whose progenitors were more limited by other factors. They suggest that targeting efficiency in CO2 assimilation under low light could be effective in increasing productivity. Limitations to C4 photosynthesis may suggest avenues for engineering, but as Arrivault et al. point out, better understanding of such a complex pathway is needed. They used mass spectrometric measurements of 13CO2 labelling kinetics, gaining a better picture of carbon flow, concentration gradients of metabolites and the pathway’s flexibility. This approach revealed a small but significant flux to photorespiration that may increase under conditions where stomata close, such as drought.


Category: Plant Biology

Jonathan Ingram & Christine Raines

Jonathan Ingram is Senior Commissioning Editor/ Science Writer for Journal of Experimental Botany. Jonathan moved from lab research into publishing and communications with the launch of Trends in Plant Science in 1995, then going on to New Phytologist and, in the third sector, Age UK and Mind.

Christine Raines is a Professor of Plant and Molecular Physiology at the University of Essex as well as being Editor in Chief of the Journal of Experimental Botany. Christine is also a member of the SEB Plant Sections Committee and the SEB Council.