doi:10.1038/nindia.2016.74 Published online 1 June 2016
Indian scientists have joined a group of multinational crop geneticists to take a fresh look1 at the genome of the humble peanut's ancestor, Arachis duranensis, thought to be the great grandpa of the cultivated variety of today.
The ancestral peanut genome was first cracked by the International Peanut Genome Initiative in 2014 but published recently in February 20162. The new study has now resequenced the genome to unravel significant new genes responsible for peanut-allergy, the plant's unique capability to reproduce beneath the ground (geocarpy) and oil formation. This resequencing will help scientists develop improved peanut varieties that give a higher pod and oil yield and are allergen-free.
Arachis hypogaea, the peanut (or groundnut) grown in fields across the world today is the result of a natural cross between two wild species, Arachis duranensis and Arachis ipaensis, that occurred north of Argentina between 4,000 and 6,000 years ago.With ancestors from two different species, today’s peanut is called a tetraploid, meaning a species carrying two separate genomes designated A and B sub-genomes.
"This study presents the draft genome of the groundnut A-genome progenitor containing 50,324 protein-coding gene models," says Rajeev Varshney, Co-Coordinator of the Genome Sequencing Project and Research Programme Director of the Genetic Gains programme at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) near Hyderabad. Varshney and his team mates were part of the international consortia that includes 51 scientists from 9 institutes in China, India, USA and Australia.
The research expands the knowledge of understudied areas of the plant and offers millions of structural variations that can be used as genetic markers for the development of improved groundnut varieties through genomics-assisted breeding, says Manish Pandey, lead author from ICRISAT on the paper.
One of the key interesting plant behaviour in peanuts is that they flower overground but, aided by a special organ called gynophore that drives the developing pod into the soil, produce fruits underground — reason why the pods are called groundnuts. The scientists tried to find the genes responsible for this unique behaviour and located 24 genes potentially responsible for this trait called 'gravitropism'.
For oil formation, they identified 1,671 genes in peanut, which compared favourably with soybean (1,695 genes) and Arabidopsis (1,291 genes).
Comparing known allergenic proteins from peanut and other crops, the scientists identified 12 new candidate allergen-encoding genes in peanut. The results would help creation of new peanut varieties that do not trigger allergies, one of most prevalent life-threatening food sensitivities, particularly among children.
1. Chen, X. et al. Draft genome of the peanut A-genome progenitor (Arachis duranensis) provides insights into geocarpy, oil biosynthesis, and allergens. P. Natl. Acad. Sci. USA (2016) doi: 10.1073/pnas.1600899113