C4 photosynthesis at 50 – from intrigue to Hall of Fame

26 Jul 2016 - By: Jonathan Ingram

C4 photosynthesis at 50 – from intrigue to Hall of Fame

Sugarcane - In text
Sugarcane. Photo: Pixabay, CC0 Public Domain

By Jonathan Ingram, Journal of Experimental Botany

C4 photosynthesis allows improved photosynthesis in warm climates, and it’s now 50 years since Hatch and Slack first described the biochemistry. Two prestigious Darwin reviews in Journal of Experimental Botany, from Robert Furbank (Walking the C4 pathway) and Rowan Sage (A portrait of the C4 photosynthetic family), look at all things C4 in this anniversary year. There’s the excitement of the science in 1966, which is likened to a TV drama script, the development of our understanding and realization of the full implications for plant breeding, and the much more recent findings, including a Hall of Fame comprising the 40 most significant C4 species.

Walking the C4 pathway: past, present, and future

A portrait of the C4 photosynthetic family on the 50th anniversary of its discovery: species number, evolutionary lineages, and Hall of Fame

It all started with sugarcane, and the identification of a four-carbon pathway for CO2 fixation and sugar formation. Hal Hatch and Roger Slack used the now-famous pulse-chase radioisotope labelling technique, building on the work of Calvin and colleagues in the previous decade. Furbank describes it all beautifully – at the heart of it this simple experimental technique, made possible through technological advancements, the accumulated body of knowledge gathered through painstaking research over many years (the timeline provided starts with the original observation of Kranz anatomy in 1884) and the personalities themselves. And then we are reminded of the diverse life forms with C4 metabolism by Sage – Hawaiian trees in the Euphorbiaceae, xerophytic and halophytic shrubs, alpine cushion plants… and no less than 6400 species of grasses and sedges. 

It is technology again which has driven the current wave of interest in C4 photosynthesis research. Particularly this has focused on its (convergent) evolution and the way in which C4 came about repeatedly from C3 in the past, with a suite of genes and related transcription factors. But it has been more about looking forwards – using that knowledge to consider the possibility of engineering C3 plants. As we all spend increasing amounts of our work and leisure time in the virtual world, Furbank notes the way in which ‘in silico mining has become a common practice for the new generation of young researchers interested in testing hypotheses on gene function and designing gene constructs for transgenic engineering.’

Something for the beermats at the next C4 meeting

Sage notes the way in which the discoveries around C4 resonate now in diverse fields – palaeontology, anthropology, global change science and bionergy policy. And he gives us the wonderful ‘C4 Hall of Fame’, 40 species selected for their importance to humans, dominance in the biosphere or other particular attributes. Other leading C4 researchers were consulted, and the results of their deliberations are fascinating. There’s maize, sorghum, all the main crops. But there’s also tumbleweed, Salsola kali, ‘C4 star in movies and song (“Drifting along with the tumbling tumbleweeds”). And Haloxylon ammodendrum from Central Asia and North Africa, whose ‘dense thickets provided fuel to the Silk Road caravans across Asia’. Or Orinus thoroldii, the world’s highest elevation C4 plant. It goes on. Something for the beermats at the next C4 meeting, perhaps, where more pivotal experiments will be penned? 

Journal of Experimental Botany publishes an exciting mix of research, review and comment on fundamental questions of broad interest in plant science. Regular special issues highlight key areas.

Author: Jonathan Ingram
Category: Science news
Jonathan Ingram - Author Profile

Jonathan Ingram

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.