A new tool has allowed researchers probe the metabolic processes occurring within the leaves, stems and roots of clementine citrus trees. The goal is to improve the yields, flavor and nutritional value of citrus and non-citrus crops.
To build the tool, the team — led by the University of California San Diego (UC San Diego) researchers — focused on the clementine. They worked in collaboration with researchers at UC Riverside and the Universidad Autónoma de Yucatán.
The strategy is to uncover new insights on how plants respond — in terms of metabolic activities in specific parts of the plant or tree — to environmental factors like temperature, drought and disease.
The tool and the comprehensive genome-scale model for Citrus clementina were published earlier this month in the journal Proceedings of the National Academy of Sciences. The paper is titled Unveiling Organ-Specific Metabolism of Citrus clementina.
“Together, we created a tool that will open the door for improved crop design and sustainable farming for Citrus clementina and a wide range of citrus and non-citrus crops,” said UC San Diego’s Karsten Zengler, corresponding author on the new paper. “Our data-driven modeling approach represents a powerful tool for citrus breeding and farming and for the improvement of crop yield and quality.”
The highly curated and validated model of clementine metabolism contains 2,616 genes, 8,653 metabolites and 10,654 reactions.
“We generated seven biomass objective functions based on organ-specific metabolomics data for leaf, stem, root and seed and experimentally validated the model — a challenge for a plant with an average lifespan of 50 years,” said Zengler. “This model represents one of the largest genome-scale models that has been built for any organism, including for humans.”
The model is called iCitrus2616. It captures Citrus clementina’s metabolism with exceptional accuracy and enables simulating economically-relevant scenarios. For example, the researchers show how specific nutrients can improve the production of starch and types of cellulose, which in turn can enhance strength and rigidity of cell walls in citrus plants. The researchers also used the new tool to demonstrate how to increase flavor-related compounds in Citrus clementina such as flavonoids. They show how flavonoids and hormones are distributed through the entire plant.
The team constrained the clementine metabolism model with gene expression data from symptomatic and asymptomatic leaf and root tissues across four seasons during citrus greening.
This project has already revealed tissue-specific metabolic adaptations and stress-response pathways under biotic stress and has provided a mechanistic understanding of disease progression.
“I envision that these types of models will aid with crop breeding efforts in the near future,” Zengler said. “With these models, we are working to make critical plant breeding efforts more reliable and also faster.”
Source: UC San Diego
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