The long lifespans of trees might be explained by an expansion of their disease-resistance genes, reports a paper published online this week in Nature Plants. This finding helps explain how some trees, such as oaks, can survive for centuries despite exposure to various threats over time.
With 450 species spread throughout Asia, Europe and America, the oak’s ubiquity and longevity have made it a cultural emblem all over the world. The trees have also supplied human societies with invaluable services, including food and shelter, since prehistoric times.
Christophe Plomion and colleagues sequenced, assembled and annotated the genome of the ‘English’, or ‘common’, oak. They then compared the sequenced oak genome with existing whole-genome sequences for other plants, including both tree and herbaceous sequences. The authors reveal that the English oak experienced a recent burst of tandem gene duplication. This event appears to have contributed to 73% of the oak’s total gene family expansion. These expanded families are largely associated with disease-resistance genes and exhibit positive selection signatures.
The oak is not alone, however. The authors also found similar disease-resistance gene expansions in various other tree genomes, relative to those of herbaceous species. The authors conclude that this parallel gene expansion suggests that the arboreal immune system plays a vital role in ensuring the trees’ longevity.