Genome of Magnolia kobus (Magnoliaceae): An Additional Key Reference for the Angiosperm Evolution

Magnolia has received keen interests from many botanists because it is believed one of early-diverging angiosperms in the evolutionary history of angiosperms. Recent molecular phylogenetic studies showed that Magnolia is placed at the “Magnoliids” clade after the Amborella, Nympheaceae, and Austrobailales in the angiosperm phylogeny. Therefore, its genome study is highlighted to understand the early diversification of angiosperms. We generated about 150 Gbp of NGS sequences from Magnolia kobus, a polular garden tree in Magnoliaceae, with six different libraries (2 pair-end and 4 mate-pair libraries). Preliminary version of genome assembly in M. kobus represents 1.77 Gbp with N20 and N50 lengths are 3,935 bp and 936 bp, respectively. The size of assembled genome moderately agrees with the estimated genome size (1.44 Gbp) based on flow-cytometry. Without masking repetitive sequences, gene prediction was executed resulting in 308,327 putative genes. Among them 93,867 genes have known functional domains, indicating that the remaining genes should be reconsidered after improving genome quality. Almost one thousand out of 93,867 genes are ”reverse transcriptase RNA-dependent DNA polymerases”, which is usually related to integrate repetitive sequences after transcription. After improving genome assembly, detailed comparison of Magnolia genome with those of other key taxa in the angiosperm evolution including Amborella will provide an understanding of genetic base of early diversification of angiosperms.