InterGgeneric and interspecific relationships in tribe Ricineae revealed by phylogenomics of plastome and transcriptome Generic relationships of the Ricinus revealed by phylogenomics of plastome and transcriptome

Wenxiang Liu ¹ Guobo Li ¹ Zhuo Zhou ² Jiafu Chen ¹ YU Anmin ¹ Aizhong Liu ¹ Junwei Ye ^1* Bin Tian ^1*

• ¹ Southwest Forestry University, Kunming, China
• ² Kunming Institute of Botany, Chinese Academy of Sciences (CAS), Kunming, Yunnan, China

The taxonomy of Euphorbiaceae is extremely difficult, especially the phylogenetic relationshipy of closed closely related genera. In Ricinus, that which embraces an important non-food oil-seed crop worldwide (Ricinus communis), Discocleidion and Speranskia are likely closely related genera base on molecular phylogenyevidence (tribe Ricineae), however the intergeneric and interspecific relationship is not well-resolved. Thus, we reassess the inter-generic and inter-specific relationship of the three generatribe through phylogenomics of plastome and transcriptome. The newly sequenced plastome chloroplast genome range from 167,327 to 190,093 bp with typical circular quadripartite structures. The longest genome of S. tuberculata may be due to expansions of the non-coding region of large single-copy and higher number of simple sequence repeats. Natural selection pressure on chloroplast genes is relatively small and the tribe is likely to experience a population contraction. The transcriptome assembly contig N50 of the tribe ranges from 1506 (D. rufescens) to 2489 bp (S. tuberculata). A total of 50,513 genes (S. cantonensis) to 78,048 genes (D. ulmifolium) were detected, and the GC content varied between 38.17% (S. cantonensis) and 40.01% (R. communis). The three genera formed a well-supported monophyletic lineage, confirmed by different genomic datamonophyletic lineage through different genomic data using maximum likelihood and Bayesian inference. Discocleidion and Ricinus are supported to be sister to each otherclosely relatedDiscocleidion and Ricinus are supported to be the most closely related. In Speranskia, S. yunnanensis diverged first and the divergence of S. tuberculata and S. cantonensis was followed. Further, Mmorphological similarities also support the monophyletic lineage and inter-generic and inter-specific relationshipsrelationship. The generic and interspecific relationships in tribe Ricineae is clearly revealed byThe phylogentic relationship of closely related genera of Ricinus is clearly revealed by genomic and morphological data, providing a genetic base basis for future comparative genomic investigations and phylogeny reconstruction of Euphorbiaceae.