Genetic improvement of grass pea (Lathyrus sativus) for low β-L-ODAP content

Emmrich, Peter (2017) Genetic improvement of grass pea (Lathyrus sativus) for low β-L-ODAP content. Doctoral thesis, University of East Anglia.

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Grass pea (Lathyrus sativus) is a legume crop with great potential for global food security
due to its exceptional tolerance to drought and flooding. The main limitation of this crop is
the presence of the toxin β-L-oxalyl-2,3-diaminopropionic acid (β-L-ODAP) in its seeds and
green tissues, which can cause paralysis in humans if grass pea is consumed over long
periods. The objective of this study was to develop means to identify grass pea genotypes
with reduced or zero seed β-L-ODAP content and to investigate the biosynthetic pathway
of this compound in grass pea. To this end, collections of grass pea germplasm were
screened for variation in seed β-L-ODAP levels. Considerable variation in β-L-ODAP levels
was observed but no β-L-ODAP-free plants were identified. To increase the available
variation for this trait, an EMS-mutagenised population was screened for low/zero-ODAP
mutants. This mutant screen yielded 14 low-ODAP mutant lines, three of which were
characterised using a mass spectrometry method, employing a stable-isotope-labelled
isoform of β-L-ODAP as an internal standard. Both the development of the mass
spectrometry method and the synthesis of the internal standard were performed for the
purposes of this project. The three characterised lines yielded seed β-L-ODAP-contents
below existing low-ODAP varieties, although none were β-L-ODAP-free. To further
investigate the synthesis of β-L-ODAP, RNA was extracted from several tissues of grass pea
and sequenced to create tissue specific transcriptomes. These were interrogated to identify
candidate genes, which were tested using heterologous expression in Nicotiana
benthamiana. One candidate gene of the BAHD-acyltransferase family was confirmed as an
enzyme capable of catalysing the synthesis of β-L-ODAP. The identification of a set of low-
ODAP mutants and the ODAP-synthase gene represent significant advances towards
understanding the role of β-L-ODAP in grass pea and the development of grass pea
genotypes free of this neurotoxin.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Jackie Webb
Date Deposited: 28 Jun 2017 12:11
Last Modified: 28 Jun 2017 12:11


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