Crop improvement through biotechnology: Targeting drought resistance and photosynthesis

The world population is projected to grow from the current 7 to about 9 billion by 2050. One of the major challenges that will face agriculture in the next few decades is sustainable food production under climate uncertainties and dwindling natural resources to meet the increased global needs for food. Plant biotechnology plays a vital role in meeting this global challenge. The goal of this research was to investigate the use of biotechnology to improve plant photosynthesis, water use efficiency and drought resistance, to either increase yield and/or alleviate the impacts of water stress on biomass and yield. In the first assay, the use of two Arabidopsis thaliana promoters, RD29A and RD29B, in soybean (Glycine max (L.) Merr.) was investigated and results suggest that they may be useful in controlling transgenes targeted to enhance drought resistance in soybean as long as there are no agronomic penalties associated with low-level expression in the absence of stress. In the second assay, the expression of AQPV1, an aquaporin gene from Chlorella virus MT325, and its effect in mitigating drought stress in tobacco (Nicotiana tabacum) was investigated. Results showed that the transformed AQPV1 plants maintained higher photosynthetic rates, less negative water and osmotic potentials, and accumulated greater biomass when subjected to drought compared to control plants. In the third assay, the potential use of C4 enzymes from Cyanobacteria to improve C3 photosynthesis was investigated. The cyanobacterial ictB (inorganic carbon transporter B) and FBP/SBPase (fructose-1,6-/sedoheptulose-1,7-biphosphatase) genes were placed under control of constitutive promoters and introduced into soybean chloroplasts via Agrobacterium-mediated transformation. The former gene is involved in HCO3− accumulation and the latter catalyzes the hydrolysis of both fructose-1,6-bisphosphate and sedoheptulose-1,7-bisphosphate in the Calvin cycle. Leaf physiological data collected in both the greenhouse and the field revealed that transgenic soybeans displayed higher leaf photosynthetic rates compared to control plants. In addition, some of the tested transgenic events performed better than control plants when exposed to soil dry-down experiments. Results from these assays contribute to the ongoing research aiming at using plant genetic manipulations to increase crop productivity and alleviate environmental stresses