Location: Food Quality Laboratory
2022 Annual Report
Objectives
Objective 1: Identify, characterize and manipulate key regulatory genes for antioxidant biosynthesis in pre- and post- harvest produce to optimize product quality and nutritive value. [NP 306, C1, PS1A]
Sub-objective 1A: Analyze global gene expression profiles in response to treatments and identify candidate genes and signaling pathways that regulate fruit ripening and biosynthesis of sugars, acids and phenylpropanoids.
Sub-objective 1B: Produce transgenic plants/fruits with increased or reduced expression of selected candidate genes, and determine their functional significance in fruit ripening and nutritive quality.
Objective 2: Identify pre-harvest parameters and develop commercially relevant treatments that enhance microgreen productivity, quality and nutritive value for urban and space farming. [NP 306, C1, PS1B]
Sub-objective 2A: Evaluate the effect of preharvest treatments on microgreen productivity, quality and nutritive value in controlled environment settings.
Sub-objective 2B: Conduct global gene expression analysis of microgreens in response to abiotic stresses encountered in space or under microgravity.
Approach
For first objective, strawberry fruit at early and late stage of fruit development will be treated with BZT and AMD, two compounds showing impact in controlling fruit color and firmness, etc. Global gene expression will be studied to identify candidate genes related to fruit ripening and biosynthesis of sugars, acids and phenylpropanoids. Selected genes can be used as functional markers for industry management and breeders. Once these genes are identified, the already commercially available treatments, such as calcium and UVB, will be applied to determine whether and how these treatments affect expression of the selected genes. The optimum treatments will be identified from two approaches and/or combination of two approaches if there is an additive or synergistic effect. Further, stable or transient transformation with silencing or over-expression gene constructs will be used to assess the function of specific genes in various aspects of fruit physiology and metabolism, including ripening, sensory parameters, responses to stresses, and accumulation and/or retention of health-beneficial secondary metabolites.
For second objective, microgreens, young vegetable seedlings with rich nutrition, such as broccoli, red radish, amaranth and pea will be selected for this study. The seeds of microgreens will be subjected by physical treatments, such as cold plasma, UVC to control pathogen infection and promote seed germination. Seedlings will be treated with different lights, UVB, and calcium and carbon dioxide. Microgreen growth and quality at the production level will be evaluated to determine the best practice for microgreen yield and quality. In collaboration with NASA, microgreen growth and quality will be studied under microgravity and high carbon dioxide. Global gene expression analysis of microgreen responses to stress both in controlled environment systems on earth and in microgravity will be investigated to determine how stress relates to yield and quality at the gene and metabolic pathway level. Putative differentially expressed genes will be used to find which genes are the better markers for future use in industry.
Progress Report
This is the second year report for Project Number 8042-43000-016-00D “Integrated Approaches to Improve Fruit and Vegetable Nutritional Quality with Improved Phenolics Contents” under National Program 306 “Product Quality and New Uses”, Component 1, Foods. Objective 1 is to identify, characterize and manipulate key regulatory genes for antioxidant biosynthesis in pre- and post- harvest produce to optimize product quality and nutritive value. Objective 2 focuses on identification of pre-harvest parameters and develop commercially relevant treatments that enhance microgreen productivity, quality and nutritive value for urban and space farming. Progress was made in both Objectives and their subobjectives.
For Objective 1, previously two types of putative plant growth regulators, carboxamide (CAD) and phenylacetamide (PAD) analogs was identified to show effective to promote and inhibit fruit development and ripening in strawberry and tomato, respectively. To understand the mechanics of CAD and PAD and identify the key target genes, transcriptome analyses were carried out. More than one hundred genes showed the significant changes in response to the chemical treatment. The genes were analyzed in silico and classified based on the known functions of them in plants. Twenty genes related to fruit development and ripening were selected as possible functional markers for breading. Further, three genes were selected for functional/transgenic study. The constructs of overexpressing and knockout were made, and transient transformation in strawberry fruit is done. Stable transformation is initiated to establish diploid and octoploid strawberry transformation. Moreover, CAD and PAD were used to test the effectiveness of potato sprouting and sweet cherry fruit ripening. The results are not clear-cut because the chemical delivery/spray was not effective. Next step is to develop new delivery approaches. Both CAD and PAD have been filed for USA patent application because of their great potential to be used by growers and industry to control fruit quality and shelf life, and reduce food waste.
In terms of Objective 2, several experiments were performed to determine the effective approaches to increase microgreen yield and nutritional quality. These approaches included cold plasma for seed treatment, temperature changes during microgreen plant growth stages, seed density changes and harvest time changes. The optimal duration (2 min-4 min) for seed cold plasma treatment was determined. Reduction of temperatures by 3-5 oC before harvest are effective for improving microgreens phenolics contents. The optimal seed densities and harvest time for certain vegetables (broccoli and radish) were determined. Effect of biofortification of selenium in broccoli on postharvest quality and shelf-life was also studied. Biofortified broccoli microgreens showed longer shelf-life. These studies will provide effective approaches to improve microgreen yield and quality for CEA and urban agriculture.
Calcium deficiency caused bone loss is a big challenge for astronauts. In collaboration with NASA, it had been found that simulated microgravity could increase broccoli microgreen yield and calcium content. In this year, transcriptome analyses were carried out to identify the critical genes involved in plant growth and calcium uptake under simulated microgravity. The bioinformatic analysis of the data is ongoing. The overall impact of this research is that astronauts and people in space have new information for achieving high yield and calcium content microgreens.
Accomplishments
1. New approach to increase selenium content and fresh matter yields of salad greens. Selenium (Se) is a mineral which plays an essential role in multiple human metabolic pathways. Plant-based foods contain Se-bound metabolites with unique functionalities for the human metabolism. ARS scientists in Beltsville, Maryland, conducted a survey of lettuce commercially grown in 15 locations across the USA and Canada and found a tendency for Se to accumulate higher (up to 10 times) in lettuce grown along the Colorado river basin region, where the country’s highest incidence of annual sunlight radiation is recorded.
Review Publications
Zhu, X., Yang, T., Sanchez, C.A., Hamilton, J.M., Fonseca, J.M. 2022. Nutrition by design: Boosting selenium content and fresh matter yields of salad greens with pre-harvest light intensity and selenium applications. Frontiers in Nutrition. https://doi.org/10.3389/fnut.2021.787085.
Han, C., Ma, M., Yang, T., Li, M., Sun, Q. 2021. Heat mediated physicochemical and structural changes of wheat gluten in the presence of salt and alkali. Journal of Agricultural and Food Chemistry. 120:106971. https://doi.org/10.1016/j.foodhyd.2021.106971.
Zhang, M., Ma, M., Yang, T., Li, M., Sun, Q. 2022. Dynamic distribution and transition of gluten proteins during noodle processing. Food Hydrocolloids. 123:107114. https://doi.org/10.1016/j.foodhyd.2021.107114.
