Format: ORAL

Xiao Feng1, Qipian Chen1,2, Weihong Wu1, Jiexin Wang1, Guohong Li1, Shaohua Xu1, Shao Shao1, Min Liu1, Cairong Zhong3, Chung-I Wu1, Suhua Shi1, Ziwen He1

1 School of Life Sciences, Sun Yat-sen University, Guangzhou, China 2 Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen, China 3 Hainan Academy of Forestry (Hainan Academy of Mangrove), Haikou, China

Whole-genome duplication (WGD), or polyploidy, events are widespread and significant in the evolutionary history of angiosperms. However, empirical evidence for rediploidization, the major process where polyploids give rise to diploid descendants, is still lacking at the genomic level. Here we present chromosome-scale genomes of the mangrove tree Sonneratia alba and the related inland plant Lagerstroemia speciosa. Their common ancestor has experienced a whole-genome triplication (WGT) approximately 64 million years ago coinciding with a period of dramatic global climate change. Sonneratia, adapting mangrove habitats, experienced extensive chromosome rearrangements post-WGT. We observe the WGT retentions display sequence and expression divergence, suggesting potential neo- and subfunctionalization. Strong selection acting on three-copy retentions indicates adaptive value in response to new environments. To elucidate the role of ploidy changes in genome evolution, we improve a model of the polyploidizationrediploidization process based on genomic evidence, contributing to the understanding of adaptive evolution during climate change.