Reducing an anti-nutritional compound in legumes to increase use of a sustainable biological nitrogen source

A project undertaken in the School of Biological Sciences, Faculty of Sciences, The University of Adelaide, and supervise by Dr. Iain Searle

Common vetch (Vicia sativa) is a leguminous, annual crop plant that provides valuable soil nitrogen to farming systems and is a palatable, cheap, high protein feed source with potential as feed for livestock and humans (1). One significant reason of its limited agricultural use is that anti-nutritional compounds exist in seeds, especially β-cyano-alanine and γ-glutamyl-β-cyano-alanine (GBA), which has high toxicity to monogastric animals, like poultry (especially), pigs, and humans (2-4). Reduction of GBA toxin from 1.6% to 0.55% was successfully achieved over a 20-year-period by using conventional plant breeding methods to generate a line, Lov2 (Tate and Searle, pers comm 2016). However, the GBA level in Lov2 is not sufficiently low enough for human, poultry or pig consumption (5). Hence an alternative approach is required to produce zero GBA vetch.

As vetch is an orphan legume with very limited molecular resources, we are developing various molecular resources in order to develop and implement a strategy to reduce the antinutritional compound GBA and accelerate Vetch improvement in the future. Recently we used a novel RNA-seq phylogenomics (molecular) approach to identify candidate casual gene(s) for GBA accumulation (Nguyen and Searle, unpublished). These genes are now the focus of our future research plans.

Project aims

In this project, we will test whether the reduction of anti-nutritional compounds in legumes can be harnessed to optimize food production- a valuable protein source. In the future, the mRNA profile of anti-nutritional compound genes with specific functions could be used as a screenable marker to select legume crops with improved nutritional profiles.

Project objectives

In this project, we will; 

  1. extensively profile genes involved in synthesis and degradation of anti-nutritional compounds in legume seeds by using established RNA-seq,
  2. demonstrate that candidate gene(s) synthesise or detoxify the anti-nutritional compound GBA in vetch seeds by using either established CRISPR-Cpf1 gene editing technology or transgenic complementation, and
  3. demonstrate that modified vetch seeds no longer have anti-nutritional effects on sensitive monogastric animals.
References
  1. Hannah, J. (1996) Growing grain vetch (FS 4/96). Primary Industries South Australia.
  2. Bell, E.A. and Tirimanna, A.S.L. (1965) Association of amino acids and related compounds in the seeds of forty-seven species of Vicia: their taxonomic and nutritional significance. Biochemical Journal. 97: 104-111.
  3. Valentine, S.C., and Bartsch, B.D. (1996) Common vetch grain as a protein supplement for dairy cows. Proceedings of the Australian Society for Animal Production. 21: 350.
  4. Resseler, C. (1962) Isolation and identification from common vetch of the neurotoxin β-cyan-L-alanine, a possible factor in neurolathyrism. The Journal of Biological Chemistry 237: 733-735.
  5. Rathjen, J. (1997) The potential of Vicia sativa L. as a grain legume for South Australia. Phd thesis submitted to the University of Adelaide.
Figure 1. Vicia sativa (common vetch) pods and seeds at different developmental stages prior to maturity.

Figure 2. Vicia sativa growing at the National Vetch Breeding Program field site in South Australia (2017).