Scientists sequence the complete genome of the olive tree

Researchers have sequenced the complete genome of the olive tree (Olea europaea) for the first time ever.

CREDIT: Manuel Sánchez (RJC-CSIC)

Their work will facilitate genetic improvement for production of olives and olive oil. The results could also lead to advancements in protecting olive trees from attacks of bacteria (Xilella fastidiosa) and fungi (Verticillium dhailae).

“Without a doubt, it is an emblematic tree, and it is very difficult to improve plant breeding, as you have to wait at least 12 years to see what morphological characteristics it will have, and whether it is advisable to cross-breed,” says Toni Gabaldón, ICREA research professor and head of the comparative genomics laboratory at the CRG. “Knowing the genetic information of the olive tree will let us contribute to the improvement of oil and olive production, of major relevance to the Spanish economy.”

The first complete sequencing of the olive tree’s DNA involved a three-year research effort coordinated by Pablo Vargas. Vargas explained more about the research: “There are three phases to genome sequencing: first, isolate all of the genes, which we published two years ago. Second, assemble the genome, which is a matter of ordering those genes one after the other, like linking up loose phrases in a book. Last, identify all of the genes, or binding the book.”

Comparing the DNA to wild olive

In addition to the complete sequencing of the olive tree genome, researchers have also compared the DNA of this thousand-year-old tree with other varieties such as the wild olive. They have also found the transcriptome, the genes expressed to determine what differences exist on the genetic expression level in leaves, roots and fruits at different stages of ripening.

The next step, researchers say, will be to decode the evolutionary history of this tree. Knowing the evolution of olive trees from different countries will make it possible to know their origins and discover the keys that have allowed it to adapt to very diverse environmental conditions. Such research will also help discover the reasons behind the extraordinary longevity of the tree (they can live for 3,000 to 4,000 years).

“That longevity makes the olive tree we have sequenced practically a living monument,” says Gabaldón. “Up to now, all of the individuals sequenced, from the fruit fly (Drosophila melanogaster) to the first human being analysed, have lived for a certain time, depending on their life expectancy, but then died or will die. This is the first time that the DNA of an individual over 1,000 years old, and that will probably live another 1,000 years, has been sequenced.”