Analysis of Michelia（Magnoliaceae）chloroplast genomes: Provide New Insights into Intergeneric and Intrageneric Relationships

Abstract

Background: Among Magnoliaceae, the genus Michelia is thesecond largest and most evolved, which is essential for studying angiosperm origins, development, and evolution. Given the taxonomic confusion among Magnolia, Manglietia, and Michelia, this study provides recommendations for some of the taxonomically confused intergeneric and intrageneric relationships based on chloroplast genomesanalysis of six Michelia plants. Results: The six chloroplast genomes were set up to range in size from 159,703 bp to 160,026 bp. It had abundant simple sequence repeat sites (136-142), and six highly variable regions (rpl32-trnL, ndhC-trnV, petA-psbL, ccsA-ndhD, rps15-ycf2, trnN-ndhF) were detected (pi>0.005). Compared with five other genomes, a shift of the rpl2 gene from the IR region to the LSC region was found only in Michelia doltsopa. In this study, 26 species of cp genome were used, and two trees establish methods were used for phylogenetic analysis of Magnoliaceae. The results showed that the two phylogenetic trees had the same topological structure. The six genera Micheliawere first grouped into a cluster, which was further separated into two sister clades. There was a clustering of Magnolia sieboldii and Manglietia insignis within the genus Michelia, while the genus Yulania tended to be more close relatedness to those species. Conclusion: Combining the results of previous morphological, sporological, and molecular marker studies, we offer a new taxonomic view to the classification of Magnoliaceae: there should be a merger between Manglietia insignis, Paramichelia baillonii, and Tsoongiodendron odor in the genus Michelia; Parakmeria yunnanensis and Pachylarnax sinica should be combined into the genus Pachylarnax. This study provides six genomic resources of Micheliathat will be beneficial for the evolutionary study and the phylogenetic construction of Magnoliaceae.