Evolution by duplication: paleopolyploidy events in plants reconstructed by deciphering the evolutionary history of VOZ transcription factors.

BACKGROUND

Facilitated by the rapid progress of sequencing technology, comparative genomic studies in plants have unveiled recurrent whole genome duplication (i.e. polyploidization) events throughout plant evolution. The evolutionary past of plant genes should be analyzed in a background of recurrent polyploidy events in distinctive plant lineages. The Vascular Plant One Zinc-finger (VOZ) gene family encode transcription factors associated with a number of important traits including control of flowering time and photoperiodic pathways, but the evolutionary trajectory of this gene family remains uncharacterized.

RESULTS

In this study, we deciphered the evolutionary history of the VOZ gene family by analyses of 107 VOZ genes in 46 plant genomes using integrated methods: phylogenic reconstruction, Ks-based age estimation and genomic synteny comparisons. By scrutinizing the VOZ gene family phylogeny the core eudicot γ event was well circumscribed, and relics of the precommelinid τ duplication event were detected by incorporating genes from oil palm and banana. The more recent T and ρ polyploidy events, closely coincident with the species diversification in Solanaceae and Poaceae, respectively, were also identified. Other important polyploidy events captured included the "salicoid" event in poplar and willow, the "early legume" and "soybean specific" events in soybean, as well as the recent polyploidy event in Physcomitrella patens. Although a small transcription factor gene family, the evolutionary history of VOZ genes provided an outstanding record of polyploidy events in plants. The evolutionary past of VOZ gene family demonstrated a close correlation with critical plant polyploidy events which generated species diversification and provided answer to Darwin's "abominable mystery".

CONCLUSIONS

We deciphered the evolutionary history of VOZ transcription factor family in plants and ancestral polyploidy events in plants were recapitulated simultaneously. This analysis allowed for the generation of an idealized plant gene tree demonstrating distinctive retention and fractionation patterns following polyploidy events.