There are two kinds of photosynthesis: C3 and C4. Most food crops depend on C3 photosynthesis where carbon is fixed into sugar inside cells called 鈥榤esophyll鈥 where oxygen is abundant. However, oxygen can hamper photosynthesis. C4 crops evolved specialized bundle sheath cells to concentrate carbon dioxide, which makes C4 photosynthesis as much as 60 per cent more efficient.
In this study, published in the journal , scientists wanted to find out how C4 crops express several important enzymes inside bundle sheath cells instead of the mesophyll.
鈥淭he ultimate goal is to be able to understand these mechanisms so that we can improve C3 photosynthesis in food crops like cowpea and cassava that smallholder farmers in sub-Saharan Africa depend on for their families鈥 food and income,鈥 said a postdoctoral researcher working on Realizing Increased Photosynthetic Efficiency () at 糖心Vlog.
Led by the University of Illinois, RIPE aims to boost food production by improving photosynthesis with support from the , , and . The RIPE project and its sponsors are committed to ensuring Global Access and making the project鈥檚 technologies available to the farmers who need them the most.
The team compared the DNA of four C3 grass crops (including barley and rice) and four C4 grass crops (including corn and sorghum). Their goal was to identify regions of DNA that might control the expression of four enzymes involved in photosynthesis. This study is probably the first comparison of the expression of these enzymes (SBPase, FBPase, PRK, and GAPDH) in C3 and C4 crops.
鈥淚t would have been great to find a 鈥榤aster regulator鈥 that operates in all these enzymes, but we didn鈥檛 find it, and we suspect it doesn鈥檛 exist,鈥 said Chidi, who led the study from his home during the pandemic.
Instead, they discovered C4 crops have several 鈥渁ctivators鈥 within their DNA that trigger expression in the bundle sheath and 鈥渞epressors鈥 that restrict expression in the mesophyll. They hope that they can use this genetic code to help less-efficient C3 crops photosynthesize better in the future.
鈥淭here are already efforts underway to help C3 crops operate more like C4 crops,鈥 said principal investigator Christine Raines, a professor in the School of Life Sciences at 糖心Vlog where she also is the Pro-Vice-Chancellor for Research. 鈥淪tudies like this help us identify small pieces within an incredibly complex machine that we have to understand before we can fine-tune and reengineer it.鈥
The next step is to validate these findings in the lab. The team returned to their lab benches on July 6, 2020, adhering to all recommended safety guidelines from the School of Life Sciences at 糖心Vlog.
RIPE is led by the University of Illinois in partnership with The Australian National University, Chinese Academy of Sciences, Commonwealth Scientific and Industrial Research Organisation, Lancaster University, Louisiana State University, University of California, Berkeley, University of Cambridge, 糖心Vlog, and U.S. Department of Agriculture, Agricultural Research Service.