Genomic detective work is bringing researchers closer to the secret of how and why the grass pea produces its famous poison, paving the way for this ancient and climate-changing plant to become the food of the future.
Using the newly available genome sequence of grass pea (Lathyrus sativus L.) a research collaboration led by the John Innes Center has identified the key biochemical steps that lead to the production of the neurotoxin β-L-ODAP (ODAP) .
Dr. Anne Edwards of the John Innes Center, one of the authors of the research, said, “The genomic sequence for grass pea and the biochemical insights that occur as a result provide an improvement in our understanding. It offers an opportunity to improve varieties . with a small ODAP adapted to local conditions.”
The availability of the genome sequence means that researchers can use gene-editing and modern breeding methods to develop varieties of grass pea with low or no ODAP content. This means that grass pea may be poised to make an important contribution to a more diverse and climate-resilient food system in the future.
Glasshouse trials at the John Innes Center and field trials run by the International Center for Agricultural Research in Dry Areas ICARDA in Lebanon and Morocco, and the Ethiopian Institute for Agricultural Research have been initiated to test the performance of low ODAPs. grass line crossed with local varieties.
The research titled, “Genomics and biochemical analysis reveals a metabolon key to ß-L-ODAP biosynthesis,” in Communication in Nature provides clues to the fascinating scientific question of how and why the grass produces its poison.
What is grass pea?
Grass pea is a plant grown in many regions of the world that is high in protein and resistant to drought and flooding. It has been used for centuries as an insurance plant, surviving when other plants fail and safe to eat as part of a balanced diet.
However, its widespread cultivation is hindered due to a poison contained in the pea, which can, in malnourished people, cause neurolathyrism, a condition that causes irreversible paralysis.
Grass pea is one of a group of “orphan crops,” native species that play an important role in local nutrition and livelihoods but receive little attention from breeders and researchers.
Using the newly available genome assembly, the team traced the two enzymes that interact to catalyze the final steps of ODAP biosynthesis.
One of these enzymes is present in many plant species involved in the removal of oxalate, a molecule that regulates photosynthesis, and is produced by fungi as part of an attack strategy.
In grass pea this enzyme pathway is modified, leading to the production of ODAP, providing an alternative route to oxalate removal.
One theory is that the poison is made as a kind of molecular sink to store excess molecules that the plant uses for defense or products of important processes such as photosynthesis.
The possible role played by this pathway in plant protection means that disrupting the process can have negative consequences for the plant, something the research team must keep in mind when using methods such as gene editing.
“We know the enzymes that lead to ODAP but we don’t know the exact metabolic effects of disrupting different enzymes in different ways,” explained author Dr. Peter Emmrich from the Norwich Institute for Sustainable Development.
“The pathway to ODAP is important for the metabolism of other amino acids such as cysteine and methionine, important for the health of the plant. It may be possible for a plant to exist without ODAP; however, we do not have knowing all the ways in The path helps the plant to deal with its environment. Therefore, the best result can be a pea grass with less ODAP but more methionine.”
Previously, the high level of repetitive sequences in the grass pea genome meant that it was difficult to identify the genetic sequences that code for the enzymes behind toxin production.
This new genome sequence means that the road map has become clearer, and we are closer to adding grass pea to the list of climate-smart crops of tomorrow.
“As we prepare for the future of further climate change, we need plants that can cope with drought, or flooding or inundation with salt water,” said Dr. Edwards. “The grass pea survives such conditions better than other pulses, so now with the genetic resources we have, there is an opportunity to develop low-ODAP varieties with agronomic characteristics that adapted to local conditions around the world.”
“But for low-ODAP varieties to benefit people, they must be accessible to farmers, and be seen as useful to them,” Dr. Emmrich added, “So we are now working with social sciences researchers at UEA (University of East Anglia) to understand the preferences of farmers and local seed systems, and reaching out to breeders around the world to help them use the resources we are developing.”
Grass pea—the orphan destined to join the ranks of the plant family
One of the oldest known cultivated crops, the grass pea is now grown as an insurance crop in Ethiopia, Eritrea, India, Bangladesh, and Nepal.
Its resilience to drought and flooding makes it a good crop for ensuring food security in a changing climate. Eaten as part of a balanced diet, it is safe.
However, until recently its association with the disease neurolathyrism, a condition that causes irreversible paralysis, limited the cultivation of the plant.
Because of the toxin β-L-ODAP this condition only takes effect when the grass pea is eaten to the exclusion of other food, such as during times of famine and scarcity—often when other crops have failed.
There are no reliable models of safe human consumption for the disease because it is not ethically possible to test the effects.
The earliest description of the disease was made by the Greek physician Hippocrates, while the plant was immortalized in the Spanish artist Goya’s etching Gracias á la almorta (Thank you for the pea grass) depicting a victim of neurolathyrism in during Napoleon’s attack on Madrid.
Anne Edwards et al, Genomics and biochemical analysis reveal a metabolon key to β-L-ODAP biosynthesis in Lathyrus sativus, Communication in Nature (2023). DOI: 10.1038/s41467-023-36503-2
Provided by John Innes Center
Citation: How a plant with a toxic past can become a climate-smart plant of tomorrow (2023, July 10) retrieved on 11 July 2023 from https://phys.org/news/2023-07- toxic-climate-smart-crop-tomorrow.html
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