The Genome Sequence of Hibiscus syriacus provides Insights of Genome Polyploidization

The Rose of Sharon (Hibiscus syriacus L.) is the national flower of Korea and one of the wide spread tree in Korea. Here we report genome sequence of H. syriacus containing 87,603 predicted genes. Total 1,748 Mb (91.9 % of 1,901 Mb) was assembled into 77,492 scaffolds and only 33 Mb (1.7% of assembled genome) was gap sequences. Orthologous gene sets containing 105,342 genes in 9,076 clusters were determined by OrthoMCL analysis with 5 genomes including Arabidopsis thaliana, Gossypium raimondii, Theobroma cacao, Amorellos trichopoda.  Using one-to-one single copy genes in gene families, we investigated an evolutionary relationship based on divergence time among Malvaceae plants. Furthermore, gene families involved in flowering time and disease resistance were highly diverged and expanded in H. syriacus genome compared to the close relatives. Functional roles of these genes were investigated. Comparison of genome structures with two Malvaceae plants (G. raimondii, T. cacao) suggested that duplication events including whole genome duplication (WGD) and tandem duplication were occurred in H. syriacus genome. The copy number variation analysis also suggested that H. syriacus genome was polyploidy genome while Gossypium raimondii and Theobroma cacao genome were diploid genome. The further studies are ongoing for providing insights of processing genome polyploidization