Genome analysis of <i>Hibiscus syriacus</i> provides insights of polyploidization and indeterminate flowering in woody plants

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P><P><I>Hibiscus syriacus</I> (L.) (rose of Sharon) is one of the most widespread garden shrubs in the world. We report a draft of the <I>H. syriacus</I> genome comprised of a 1.75 Gb assembly that covers 92% of the genome with only 1.7% (33 Mb) gap sequences. Predicted gene modeling detected 87,603 genes, mostly supported by deep RNA sequencing data. To define gene family distribution among relatives of <I>H. syriacus</I>, orthologous gene sets containing 164,660 genes in 21,472 clusters were identified by OrthoMCL analysis of five plant species, including <I>H. syriacus</I>, <I>Arabidopsis thaliana, Gossypium raimondii, Theobroma cacao</I> and <I>Amborella trichopoda.</I> We inferred their evolutionary relationships based on divergence times among Malvaceae plant genes and found that gene families involved in flowering regulation and disease resistance were more highly divergent and expanded in <I>H. syriacus</I> than in its close relatives, <I>G. raimondii</I> (DD) and <I>T. cacao</I>. Clustered gene families and gene collinearity analysis revealed that two recent rounds of whole-genome duplication were followed by diploidization of the <I>H. syriacus</I> genome after speciation. Copy number variation and phylogenetic divergence indicates that WGDs and subsequent diploidization led to unequal duplication and deletion of flowering-related genes in <I>H. syriacus</I> and may affect its unique floral morphology.</P>