Carotenoids and Apocarotenoids in Planta: Their Role in Plant Development, Contribution to the Flavour and Aroma of Fruits and Flowers, and Their Nutraceutical Benefits

Carotenoids and apocarotenoids are diverse classes of compounds found in nature and are important natural pigments, nutraceuticals and flavour/aroma molecules. Improving the quality of crops is important for providing micronutrients to remote communities where dietary variation is often limited. Carotenoids have also been shown to have a significant impact on a number of human diseases, improving the survival rates of some cancers and slowing the progression of neurological illnesses. Furthermore, carotenoid-derived compounds can impact the flavour and aroma of crops and vegetables and are the origin of important developmental, as well as plant resistance compounds required for defence. In this review, we discuss the current research being undertaken to increase carotenoid content in plants and research the benefits to human health and the role of carotenoid derived volatiles on flavour and aroma of fruits and vegetables. View Full-Tex

CRISPR/Cas9-mediated mutagenesis of phytoene desaturase in diploid and octoploid strawberry

Background: Gene editing using CRISPR/Cas9 is a simple and powerful tool for elucidating genetic controls and for crop improvement and its use has been reported in a growing number of important food crops, including recently Fragaria. In order to inform application of the technology in Fragaria, we targeted the visible endogenous marker gene PDS (phytoene desaturase) in diploid Fragaria vesca ssp. vesca ‘Hawaii 4’ and octoploid F. × ananassa ‘Calypso’. Results: Agrobacterium-mediated transformation of leaf and petiole explants was used for efficient stable integration of constructs expressing plant codon-optimised Cas9 and single guide sequences under control of the Arabidopsis U6-26 consensus promoter and terminator or Fragaria vesca U6III regulatory sequences. More than 80% (‘Hawaii 4’) and 50% (‘Calypso’) putative transgenic shoot lines (multiple shoots derived from a single callus) exhibited mutant phenotypes. Of mutant shoot lines selected for molecular analysis, approximately 75% (‘Hawaii 4’) and 55% (‘Calypso’) included albino regenerants with bi-allelic target sequence variants. Our results indicate the PDS gene is functionally diploid in ‘Calypso’. Conclusion: We demonstrate that CRISPR/Cas9 may be used to generate biallelic mutants at high frequency within the genomes of diploid and octoploid strawberry. The methodology, observations and comprehensive data set pre- sented will facilitate routine application of this technology in Fragaria to single and multiple gene copy targets where mutant phenotypes cannot be identified visually

Overexpression of the RieskeFeS protein increasese electron transport rates and biomass yield

In this study, we generated transgenic Arabidopsis (Arabidopsis thaliana) plants overexpressing the Rieske FeS protein (PetC), a component of the cytochrome b6f (cyt b6f) complex. Increasing the levels of this protein resulted in concomitant increases in the levels of cyt f (PetA) and cyt b6 (PetB), core proteins of the cyt b6f complex. Interestingly, an increase in the levels of proteins in both the photosystem I (PSI) and PSII complexes also was seen in the Rieske FeS overexpression plants. Although the mechanisms leading to these changes remain to be identified, the transgenic plants presented here provide novel tools to explore this. Importantly, overexpression of the Rieske FeS protein resulted in substantial and significant impacts on the quantum efficiency of PSI and PSII,electron transport, biomass, and seed yield in Arabidopsis plants. These results demonstrate the potential for manipulating electron transport processes to increase crop productivity

Feeding the world: improving photosynthetic efficiency for sustainable crop production

A number of recent studies have provided strong support demonstrating that improving the photosynthetic processes through genetic engineering can provide an avenue to improve yield potential. The major focus of this review is on improvement of the Calvin–Benson cycle and electron transport. Consideration is also given to how altering regulatory process may provide an additional route to increase photosynthetic efficiency. Here we summarize some of the recent successes that have been observed through genetic manipulation of photosynthesis, showing that, in both the glasshouse and the field, yield can be increased by >40%. These results provide a clear demonstration of the potential for increasing yield through improvements in photosynthesis. In the final section, we consider the need to stack improvement in photosynthetic traits with traits that target the yield gap in order to provide robust germplasm for different crops across the globe

Multigene manipulation of photosynthetic carbon assimilation increases CO2 fixation and biomass yield in tobacco

Over the next 40 years it has been estimated that a 50% increase in the yield of grain crops such as wheat and rice will be required to meet the food and fuel demands of the increasing world population. Transgenic tobacco plants have been generated with altered combinations of sedoheptulose-1,7-bisphosphatase, fructose-1,6-bisphosphate aldolase, and the cyanobacterial putative-inorganic carbon transporter B, ictB, of which have all been identified as targets to improve photosynthesis based on empirical studies. It is shown here that increasing the levels of the three proteins individually significantly increases the rate of photosynthetic carbon assimilation, leaf area, and biomass yield. Furthermore, the daily integrated measurements of photosynthesis showed that mature plants fixed between 12-19% more CO2 than the equivalent wild-type plants. Further enhancement of photosynthesis and yield was observed when sedoheptulose-1,7-bisphosphatase, fructose-1,6-bisphosphate aldolase, and ictB were over-expressed together in the same plant. These results demonstrate the potential for the manipulation of photosynthesis, using multigene-stacking approaches, to increase crop yields

Comparison of Carotenoid Content, Gene Expression and Enzyme Levels in Tomato (Lycopersicon esculentum) Leaves

Physiological conditions which lead to changes in total carotenoid content in tomatoplantlets were identified. Carotenoid levels were found to increase after the onset of a darkperiod during a normal 24h cycle. This rapid initial increase is followed by a steady decreasein carotenoid content throughout the night. A decrease in the expression of several caroteno-genic genes, namelypds,zds(carotenoid desaturases) andptox(plastid terminal oxidase),was observed following the removal of the light (when carotenoid content is at its highest).An increase in gene expression was observed before the return to light forpdsandzds(whencarotenoid levels were at their lowest), or following the return to light forptox.The phytoenedesaturation inhibitor norflurazon leads to a decrease coloured carotenoid content and, inthe light, this correlated withpdsandzdsgene induction. In the dark, norflurazon treatmentled to only a weak decrease in carotenoid content and only a small increase inpdsandzdsgene expression. The striking absence of phytoene accumulation under norflurazon treatmentin the dark suggests a down-regulation of carotenoid formation in darkness. However, pro-longed dark conditions, or treatment with photosynthetic inhibitors, surprisingly led to highercarotenoid levels, which correlated with decreased expression of most examined genes. Inaddition to light, which acts in a complex way on carotenoid accumulation and gene expres-sion, our results are best explained by a regulatory effect of carotenoid levels on the expres-sion of several biosynthetic genes. In addition, monitoring of protein amounts for phytoenedesaturase and plastid terminal oxidase (which sometimes do not correlate with gene expres-sion) indicate an even more complex regulatory pattern

The Calvin-Benson-Bassham cycle in C4 and Crassulacean acid metabolism species

The Calvin-Benson-Bassham (CBB) cycle is the ancestral CO assimilation pathway and is found in all photosynthetic organisms. Biochemical extensions to the CBB cycle have evolved that allow the resulting pathways to act as CO concentrating mechanisms, either spatially in the case of C photosynthesis or temporally in the case of Crassulacean acid metabolism (CAM). While the biochemical steps in the C and CAM pathways are known, questions remain on their integration and regulation with CBB cycle activity. The application of omic and transgenic technologies is providing a more complete understanding of the biochemistry of C and CAM species and will also provide insight into the CBB cycle in these plants. As the global population increases, new solutions are required to increase crop yields and meet demands for food and other bioproducts. Previous work in C species has shown that increasing carbon assimilation through genetic manipulation of the CBB cycle can increase biomass and yield. There may also be options to improve photosynthesis in species using C photosynthesis and CAM through manipulation of the CBB cycle in these plants. This is an underexplored strategy and requires more basic knowledge of CBB cycle operation in these species to enable approaches for increased productivity. [Abstract copyright: Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.

Fruit ripening: dynamics and integrated analysis of carotenoids and anthocyanins

Background: Fruits are vital food resources as they are loaded with bioactive compounds varying with different stages of ripening. As the fruit ripens, a dynamic color change is observed from green to yellow to red due to the biosynthesis of pigments like chlorophyll, carotenoids, and anthocyanins. Apart from making the fruit attractive and being a visual indicator of the ripening status, pigments add value to a ripened fruit by making them a source of nutraceuticals and industrial products. As the fruit matures, it undergoes biochemical changes which alter the pigment composition of fruits. Results: The synthesis, degradation and retention pathways of fruit pigments are mediated by hormonal, genetic, and environmental factors. Manipulation of the underlying regulatory mechanisms during fruit ripening suggests ways to enhance the desired pigments in fruits by biotechnological interventions. Here we report, in-depth insight into the dynamics of a pigment change in ripening and the regulatory mechanisms in action. Conclusions: This review emphasizes the role of pigments as an asset to a ripened fruit as they augment the nutritive value, antioxidant levels and the net carbon gain of fruits; pigments are a source for fruit biofortification have tremendous industrial value along with being a tool to predict the harvest. This report will be of great utility to the harvesters, traders, consumers, and natural product divisions to extract the leading nutraceutical and industrial potential of preferred pigments biosynthesized at different fruit ripening stages

Fruit Development in Sweet Cherry

Fruits are an important source of vitamins, minerals and nutrients in the human diet. They also contain several compounds of nutraceutical importance that have significant antioxidant and anti-inflammatory roles, which can protect the consumer from diseases, such as cancer, and cardiovascular disease as well as having roles in reducing the build-up of LDL-cholesterol in blood plasma and generally reduce the risks of disease and age-related decline in health. Cherries contain high concentrations of bioactive compounds and minerals, including calcium, phosphorous, potassium and magnesium, and it is, therefore, unsurprising that cherry consumption has a positive impact on health. This review highlights the development of sweet cherry fruit, the health benefits of cherry consumption, and the options for increasing consumer acceptance and consumption

Options for the generation of seedless cherry, the ultimate snacking product

Cherry fruit contain a large stone and seed, making processing of the fruit laborious and consumption by the consumer challenging, inconvenient to eat ‘on the move’ and potentially dangerous for children. Availability of fruit lacking the stone and seed would be potentially transformative for the cherry industry since such fruit would be easier to process and would increase consumer demand because of the potential reduction in costs. This review will explore the background of seedless fruit, in the context of the ambition to produce the first seedless cherry, carry out an in-depth analysis of the current literature around parthenocarpy in fruit and discuss the available technology and potential for producing seedless cherry fruit as an ‘ultimate snacking product’ for the 21st century