Although whole genome duplication (WGD) has been suggested to facilitate adaptive evolution and diversification, the role of specific WGD events in promoting diversification and adaptation in angiosperms remains poorly understood. Primulina, a species-rich genus with > 180 species associated with limestone karst habitat, constitutes an ideal system for studying the impact of WGD events on speciation and evolutionary adaptation. We sequenced and assembled a chromosome-level genome of the cave-dwelling species P. huaijiensis to study gene family expansion and gene retention following WGDs. We provide evidence that P. huaijiensis has undergone two WGDs since the γ triplication event shared by all eudicots. In addition to a WGD shared by almost all Lamiales (L event), we identified a lineage-specific WGD (D event) that occurred in the early Miocene around 20.6-24.2 Myr ago and that is shared by almost the entire subtribe Didymocarpinae. We found that gene retentions following the D event led to gene family proliferation (e.g. WRKYs) that probably facilitated adaptation to the high salinity and drought stress in limestone karst. Our study highlights the role of lineage-specific WGD in species diversification and adaptation of plants from special habitats.
Keywords: Primulina huaijiensis; chromosome-level genome; differential gene retention; gene family expansion; karst habitat adaptation; whole genome duplication.
© 2020 The Authors. New Phytologist © 2020 New Phytologist Trust.