What makes plants tough enough to deal with a bad climate?
Most of the staple crops like rice, wheat or barley are C3 plants. C4 plants, like maize, enjoy the biochemical and anatomical (Kranz anatomy) innovations that make them more efficient at water and nitrogen use. Therefore, their yield is generally higher even in hot and dry climates. Due to degradation of arable lands, climate change and increasing population size, the pressure on agricultural production systems is becoming more intense day by day. One strategy to improve the productivity of staple crops is to endow them with C4 photosynthesis traits. According to a new study reported in Nature Biotechnology, a group of scientists have been successful in engineering C4 traits into C3 plant. This makes the C3 plants stronger so they can withstand harsh conditions like drought, heat and nutrient limitations.
What makes a C4 tougher than a C3?
So, for people who don’t know much about the plant physiology, these may just appear as numbers. But what are C3 and C4 plants? C3 photosynthesis uses the three-carbon molecule 3-phosphoglycerate (3-PGA) for carbon fixation whereas C4 photosynthesis utilizes a four-carbon molecule — oxaloacetate (OAA). OAA is transported from the outer mesophyll (ME) cells to inner bundle sheath (BS) cells in the form of malate or aspartate. Rice, wheat or barley is example of a C3 plant whereas maize and sugarcane are C4 plants. Since C3 plants evolved into C4 due to global reduction of CO2 level in the atmosphere, the problem of increasing food crisis globally could be solved if the engineering principles could be used to transform C4 traits into C3.
Improving the machinery of the leaf
According to the findings, scientists have been successful in developing a statistical method to simultaneously examine maize and rice expression profile. By sampling maize and rice leaves at similar points in development, they were able to examine convergent and divergent components of C3 and C4 differentiation. The leaf is the main photosynthetic machinery which drives sugar production and yield; therefore, it serves as a model to understand the process of differentiation of photosynthetic tissues. In the present study, the leaf transcriptomes or expression patterns of C4 plant (maize) and C3 plant (rice) was studied to identify new structural and regulatory components important in photosynthesis. By analyzing the metabolic profiles of the two, a mathematical model was developed to directly compare two related grass species undergoing similar development profile. Using cis-regulatory mining tools some important candidate motifs were identified which were recruited during evolution of C4 photosynthesis.
Small steps towards strong rice
The developed tools and methodology in this study provide a platform for future research, that will help to engineer improvements in carbon fixation and ultimately engineer C4 traits into C3 grasses. In the end, rice is still a C3 plant. These small steps, made by the hard work of scientist, might one day turn the C3 into a strong, climate resistant, C4 plant. Imagine what that might do for rice production and the world’s food problems. Amen!
References
Wang L, Czedik-Eysenberg A, Mertz RA, Si Y, Tohge T, Nunes-Nesi A, Arrivault S, Dedow LK, Bryant DW, Zhou W, Xu J, Weissmann S, Studer A, Li P, Zhang C, LaRue T, Shao Y, Ding Z, Sun Q, Patel RV, Turgeon R, Zhu X, Provart NJ, Mockler TC, Fernie AR, Stitt M, Liu P, & Brutnell TP (2014). Comparative analyses of C4 and C3 photosynthesis in developing leaves of maize and rice. Nature biotechnology, 32 (11), 1158-65 PMID: 25306245
rice, genetic modification, plant, maize, c3, c4, food, agriculture, climate change, photosynthesis, leaf, food economy
