Transgenic studies have demonstrated any decrease in any one of the key enzymes of the CBC has a significant negative impact on the rate of carbon assimilation and plant growth. in the 1950s, involves 11 enzymes, which catalyse 13 different steps ( Figure 1). The cycle, elucidated by Melvin Calvin et al. The CBC is subdivided into three stages, carboxylation, reduction and regeneration. In this review, we will focus on the impact of a multi-target approach to improving photosynthesis and potential impacts on nutrient value of transformed crops. A recent comprehensive review by Simkin et al. Enhancing photosynthesis, electron transport and photorespiration has been accepted as a key target for increasing crop productivity. Found in all photosynthetic organisms, Rubisco has been identified as a target for genetic manipulation and has thus been widely reviewed to date. These pathways are centred on the catalytic activity of Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase R Figure 1), a complex stromal enzyme which accounts for more than 50% of all leaf protein and 25% of leaf nitrogen. Carbon assimilation in plants involves two closely associated pathways, 1, the Calvin–Benson cycle (CBC) and 2, Photorespiration. A key determinant of this is the efficiency at which light is A, captured and B, converted into yield (i.e., biomass or grain). Crop yield is determined by the collective rate of photosynthesis over the growing season. Furthermore, all the fuel derived from oil was originally derived from photosynthates and accounts for as much as 90% of current energy production. Photosynthesis is responsible, either directly through plant growth or indirectly through the food chain, for all the food consumed worldwide. This may be achieved through improving photosynthesis through genetic manipulation ( Section 2). To increase yields whilst protecting the environment, the development of new varieties of key crops is essential. To mitigate environmental damage, it will be necessary to meet global food demands without increasing the amount of cultivatable land. Increasing cultivatable land also comes at the cost of increased fertiliser and pesticide use which creates further damage to both marine and freshwater ecosystems and results in a significant increase in greenhouse gas emissions. One avenue, clearing land for crop production, has the significant drawback of causing environmental damage to unique habitats, resulting in a global loss in biodiversity. It has been estimated that a 70% to a 100% increase in the yield of crops such as wheat, soybean ( Glycine max) and maize ( Zea mays) will be required to meet these needs. To meet the ever-growing requirements for both food and fuel, it will be necessary to develop new varieties of crops with higher yields. By 2050, it is expected that the global population will exceed 9 billion. Most of these increases came about from the breeding of higher yielding varieties and advances in agronomic approaches, as well as improving yields by exploiting the natural photosynthetic variation in key crops however, more recently the yields of several important food crops have plateaued. Over the last 70 years, agricultural yields have risen at a level that meets global demand. In this review, we discuss the current research being undertaken to improve photosynthesis and biofortify key crops to secure future food supplies and the potential links between improved photosynthesis and nutritional quality. Recent research has shown that growing plants under elevated can lead to an increase in Vitamin C due to changes in gene expression, demonstrating one potential route for plant biofortification. A number of methods to achieve this have been investigated over recent years, from improving photosynthesis through genetic engineering, to breeding new higher yielding varieties. Improving the nutritional quality of crops has become a target for providing the micronutrients required in remote communities where dietary variation is often limited. By the later part of the century, current estimates indicate that a >50% increase in the yield of most of the important food crops including wheat, rice and barley will be needed to maintain food supplies and improve nutritional quality to tackle what has become known as ‘hidden hunger’. Increasing demands for food and resources are challenging existing markets, driving a need to continually investigate and establish crop varieties with improved yields and health benefits.
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