Enhancing soybean photosynthetic CO2 assimilation using a cyanobacterial membrane protein, ictB

Authors: Hay, William; BIHMIDINE, SAADIA - University Of Nebraska; MUTLU, NEDIM - University Of Nebraska; WEEKS, DONALD - University Of Nebraska; CLEMENTE, TOM - University Of Nebraska; LONG, STEPHEN - University Of Illinois; HOANG, KHANG - University Of Nebraska; AWADA, TALA - University Of Nebraska

Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/11/2017
Publication Date: 2/16/2017
Publication URL: http://handle.nal.usda.gov/10113/5648894
Citation: Hay, W.T., Bihmidine, S., Mutlu, N., Weeks, D.P., Clemente, T.E., Long, S.P., Hoang, K.L., Awada, T. 2017. Enhancing soybean photosynthetic CO2 assimilation using a cyanobacterial membrane protein, ictB. Journal of Plant Physiology. 212: 58-68.

Interpretive Summary: In this research, a method was found to increase the yield of soybean plants using genetic engineering of a novel gene. With the world population projected to grow from the current 8 to over 9 billion by 2050, increased food production is essential. There is a direct relationship with the amount of photosynthesis that a plant can achieve and the yield the plant provides at harvest. One of the main factors that influences the photosynthesis of a plant is its inherited genetic make-up. The plant’s genes can be manipulated to result in increased photosynthetic activity and thus higher yield. By inserting a gene, termed ictB, a cyanobacterial transgene, into a soybean plant, it was found that photosynthesis and yield were increased. Soybean is the world’s fourth most important crop in regards to global quantities of seed or grain produced, and contributes $145 billion to the world’s economy. Thus, improving its productivity is vital to meeting the growing demands for food and feed while providing a significant economic contribution to the world’s economy. By increasing the yield of soybeans per acre, all participants in the value chain will benefit. In addition, the increased production will help feed the ever growing population.

Technical Abstract: Soybean C3 photosynthesis can suffer a severe loss in efficiency due to photorespiration and the lack of a carbon concentrating mechanism (CCM) such as those present in other plant species or cyanobacteria. Transgenic soybean (Glycine max cv. Thorne) plants constitutively expressing cyanobacterial ictB (inorganic carbon transporter B) gene were generated using Agrobacterium-mediated transformation. Although it is now clear that ictB does not actively transport HCO3-/CO2, there is nevertheless mounting evidence that transformation with this gene can increase higher plant photosynthesis. The hypothesis that expression of the ictB gene would improve photosynthesis, biomass production, and seed yield in soybean was tested in two independent replicated greenhouse and field trials. Results showed significant increases in photosynthetic CO¬2 uptake (Anet) and dry mass in transgenic relative to wild type (WT) control plants in both the greenhouse and field trials. Transgenic plants also showed increased photosynthetic rates and biomass production during a drought mimic study. The strongest evidence that ictB is acting to increase passive diffusion of inorganic carbon to Rubisco is provided by the observed significant increase in the maximum quantum yield of CO2 uptake, for which an increase in CO2 concentration [CO2] at the site of Rubisco is the only plausible explanation. The findings presented herein demonstrate that ictB, as a single-gene, contributes to enhancement in various yield parameters in a major commodity crop and point to the significant role that biotechnological approaches to increasing photosynthetic efficiency can play in helping to meet increased global demands for food.