Analysis of the olive genome

• Autores: Irene Consuelo Julca Chávez
• Directores de la Tesis: Juan Antonio Gabaldón Estevan (dir. tes.), Pablo Vargas Gómez (codir. tes.), Josep Allué Creus (tut. tes.)
• Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2017
• Idioma: español
• Tribunal Calificador de la Tesis: Heinz Himmelbauer (presid.), Jordi Garcia Mas (secret.), Concha Muñoz (voc.)
• Programa de doctorado: Programa de Doctorado en Biología y Biotecnología Vegetal por la Universidad Autónoma de Barcelona
• Materias:
  • Ciencias de la vida
    • Genética
    • Biología vegetal (botánica)
      • Genética vegetal
• Enlaces
  • Tesis en acceso abierto en:  TESEO  TDX 
• Resumen

  • The olive tree (Olea europaea, Oleaceae) is an iconic plant of Mediterranean countries for cultural, historical and biological reasons. The olive species comprises six subspecies (europaea, maroccana, cerasiformis, laperrinei, guanchica, and cuspidata) that together form the so-called O. europaea complex. Likewise, the subsp. europaea is divided into two taxonomic varieties: var. europaea, that comprises all the cultivated forms, and var. sylvestris (also called oleaster), that includes the wild forms. The olive tree has been intensively cultivated since 6,000 years ago, coinciding with the emergence of early Mediterranean civilizations. Because of the interest of the drupes both as table olives and as raw material to produce olive oil, the olive tree is an essential crop across the Mediterranean basin. This doctoral thesis aims to provide insights into the biology and the evolution of the cultivated olive and relatives. To this end, we sequenced, assembled, and annotated a reference genome obtained from a single individual (O. europaea L. var. europaea). Phylogenomic analysis and assessment of allelic relative coverage suggest up to four polyploidization events in the evolutionary history of the olive. Two ancient allopolyploidization events at the base of the family Oleaceae (Eocene-Late Cretaceous), and the tribe Oleeae (Oligocene-Miocene), followed by two polyploidizations in the ancestor of O. europaea (Miocene-Pliocene) since its divergence from Phillyrea angustifolia. In order to study the diversity and phylogenetic relationships in the O. europaea complex, we additionally sequenced the genome of at least one individual per subspecies. Our results show that cultivated olive trees exhibit less nucleotide diversity when compared with wild relatives. Different sets of genes were found to be under positive selection in each cultivar included in this study (‘Arbequina’, ‘Beladi’, ‘Farga’, ‘Picual’, ‘Sorani’). In addition to hybridization involving polyploidization (allopolyploidization), phylogenomic analysis revealed extensive homoploid hybridization among lineages of the O. europaea complex, which results in a continuous gene flow from wild to domesticated olive trees. In particular, cv. ‘Farga’ has a different origin than the other cultivars included in this study, and shows evidence for secondary domestication events in the Iberian Peninsula. In summary, this study helps unravel the evolutionary history of O. europaea, and uncover a complex scenario of polyploidization and hybridization that resulted in recurrent gene duplications.