Recursive paleohexaploidization shapes the durian genome.

Durian genome becomes available recently and revealed two paleopolyploidization events, which were inferred to share with cotton. Here, we reanalyzed the durian genome in comparison with other well-characterized genomes. We found that durian and cotton were actually affected by different polyploidization events: hexaploidization in durian lineage ~19-21 million years ago (mya) and decaploidization in cotton ~13-14 mya. Previous problematic interpretation might be caused by elevated evolutionary rates in cotton genes due to the decaploidization, and insufficient consideration of the complexity of plant genomes. The decaploidization considerably elevated evolutionary rates so that cotton genes evolve ~64% faster than durian ones, and explained a previous ~4 times over dating of the event. In contrast, the hexaploidization has not prominently elevated durian gene rates likely due to the negative correlation with its long generation time. Moreover, divergent evolutionary rates should also be responsible for 98.4% of reconstructed phylogenetic trees of homologous genes being incongruent with expected topolopy. These findings provided further insight into the roles played by polypoidization to the evolution of genomes and genes and raised necessity to revisit existing reconstructed phylogenetic trees.