132 Ancient Genome Duplications in Flowering Plants Clustered Around Nine Periods of Global Environmental Upheaval

Genome duplication has occurred in many flowering plants, with extra copies of genetic instructions apparently helping them survive periods of extreme environmental stress. Researchers analysed the genomes of 470 angiosperm species to develop an evolutionary tree spanning roughly 150 million years of angiosperm evolution. The team detected and dated 132 occasions when genomes duplicated long ago.

These 132 genome duplications clustered into nine prehistoric periods between 108 million and 14 million years ago. Almost all genome duplications coincided with major environmental or geological events such as climate change, changing oxygen levels or mass extinctions. One coinciding event was the asteroid impact at the end of the Cretaceous Period that killed off the non-avian dinosaurs.

A third of angiosperms today are polyploid, said Hengchi Chen at the University of Göttingen in Germany. Most polyploid organisms went extinct during long-term evolution, Chen added. Previous analyses suggested that old duplications are fairly rare.

The new findings challenge that view by showing repeated bursts of polyploidy aligned with global chaos. Normally organisms that reproduce sexually have two copies of their chromosomes. Polyploidy results from the genome failing to halve in the reproductive cells.

Plants like potatoes and some wheat varieties have four copies of their chromosomes while some plants might have eight copies or more. In times of turmoil, polyploid plants appeared to gain advantages. Extreme heat or cold may have increased the chances of a misfiring during reproduction, encouraging the rate of polyploidy to rise.

Polyploids can also have boosted resilience to stress factors like drought and salt exposure, and their extra genes might evolve new functions in a rapidly changing world. “The originally minor, polyploid individual that hides in the corner of the population somehow gets access to more resources, and it can also have this fitness advantage for the stress,” said Hengchi Chen, leading to greater survival.

Angiosperms’ hyper-flexible, redundant genomes may be key to their success as a group, Chen stated.

Changing ecosystems create new opportunities as competitors vanish. Pamela Soltis at the Florida Museum of Natural History in Gainesville questioned how larger sampling over a wider diversity of angiosperm species might affect the results. “Despite the fact that this analysis is huge compared to previous work, 470 species is still only a very small fraction of angiosperm species,” she said.

The total is close to 400,000, but new genomes are becoming available at a very rapid pace. 008. @NewScientist reported on the findings.