CE02 - Terre vivante

Adaptive introgression in Pearl Millet – PEMILADAPT

Submission summary

Understanding how species adapt is paramount to biodiversity. Species/populations adaptive potential largely depends on their genetic variability, which relies either on standing genetic variation or on de novo mutation. However, if rates of environmental changes are too rapid, occurrence of de novo mutations might be too slow of a process. When gene flow between species/populations occurs through recurrent backcrosses over generations, allowing foreign DNA to become part of recipient species’ genetic pool, it is named genetic introgression. If the genetic introgression from donor species/population increases the fitness of the recipient species/population then it is called “Adaptive Introgression" (AI). Despite the occurrence of hybridization in nature, relatively limited evidences supporting AI have been gathered until recently. Striking evidences of AI were found between archaic and modern humans. For crops, wild relatives represent a reservoir of adaptations that could refuel crops genetic diversity. With the advance of genomics, it is becoming evident that wild-crops gene flow was far more complex and protracted than previously considered. A compelling example of the potential adaptive outcome of introgression is the adaptation to altitude acquired by highland maize landraces from wild populations. Nonetheless, conclusive evidence for AI is restricted to a limited number of cases. For AI to take place, we will first need crosses and introgression to be successful. When selection against hybrids is weak and backcrosses are possible, genomic heterogeneity in terms of permeability to gene flow will affect introgression rates. Gaps knowledge on the genomic heterogeneity to introgression need to be fulfil particularly for crops. In addition, most evidence for AI comes from hard-selective sweeps, while soft-selective sweeps might be the dominant mode of adaptation. The main objective of the PEMILADAPT project is to understand how introgression from wild relatives can favour crops adaptation. The PEMILADAPT projects aims at responding the following specific questions:
1) How frequent wild introgression is and how is it distributed along the cultivated genome?
2) What modes (hard vs. soft) of selection are acting on introgressed alleles?
3) What are the functional implications of wild introgression in the cultivated genome?
To answer the above questions, we will focus on the pearl millet crop (Pennisetum glaucum). Pearl millet is the sixth most important cereal grain worldwide and it is a key cereal in arid and semi-arid regions where it is a staple food for over 90 million small farmers. Wild and cultivated pearl millet are found in sympatry and gene flow between the two forms is well recognized. By taking the opportunities coming from cutting edge technologies for high-throughout genomic sequencing and for artificial intelligence for powerful machine learning approaches, the project PEMILADAPT is expected to be at the leading front of evolutionary research questions. In addition to the fundamental knowledge on evolution that PEMILADAPT will produce, it may have significant impacts for on–going worldwide environmental challenges and sustainable development. Understanding selection forces and genomic landscape of introgression will likely help breeders in improving efficiency of their breeding strategies to adapt future varieties to on-going climate changes.

Project coordinator

Madame Cécile Berthouly-Salazar (Diversité, adaptation et développement des plantes)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

DIADE Diversité, adaptation et développement des plantes
CBGP Centre de Biologie pour la Gestion des Populations
CBGP Centre de Biologie pour la Gestion des Populations

Help of the ANR 280,280 euros
Beginning and duration of the scientific project: January 2020 - 48 Months

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