Format: ORAL

Lei Duan1, Hong-Feng Chen1, AJ Harris1, Jun Wen2

1 South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China 2 Department of Botany, Smithsonian Institution, Washington, USA

An abrupt, dramatic global cooling event occurred during the short period of the Eocene-Oligocene transition (EOT). This paleoclimatic event drove a large-scale aridification and increasingly seasonality, which drasticallyinfluenced the evolution of plants and distribution of global vegetation, especially, the great retreating of boreotropical flora. However so far, previous biogeographic studies have not well interpreted the molecular mechanism of the influence on terrestrial plants. The leguminous tribes Glycyrrhizeae (the liquorice tribe), Adinobotryeae and Wisterieae (the Wisteriatribe) formed a clade, widely distributed in every continent except for Antarctica. Based on the data of orthologous nuclear genes and chloroplast genomes from deep next-generation sequencing, and using the interdisciplinary analyses of historical biogeography, molecular ecology and phylogenomics, our study revealed that the common ancestor of the three-tribe clade existed in boreotropical regionduring the Eocene, and experiencedinter-tribal divergence, rapid niche evolution and biome shift from humid tropical forest to drier grassland or desert at the EOT. Subsequently, adaptive evolution occurred to many taxa of the clade, especially those of Glycyrrhizeae, to survive the changing habitats. On the other hand, the EOT global cooling differentiated the plant habits among the three tribes: herbs for Glycyrrhizeae, trees for Adinobotryeae and woody lianas for Wisterieae. To better investigate the noticeable point, with the annotated whole genomes obtained from the third-generation sequencing of representatives for each of the tribes, this study assessed the genome structure change and the evolution of the key gene families, whose function wasto regulate the trait of habits by influencing the biosyntheses of cellulose and lignin. With the three tribes as a model,our results can provide a reference to the studies on plant evolution under the present background of global environmental changes.