Genome Sequencing of the Charophycean Green Alga, Chara braunii

Charophycean green algae are the closest living relatives to land plants. Among them, Charales show complex differentiation of organs and tissues in the gametophyte generation; namely, rhizoids, thalli, and sexual organs, antheridia and oogonia (archegonia). Genome sequences of these organisms would be pivotal to understand how land plants evolved from green algae. We selected the species Chara braunii as the target of genome analysis based on its relatively small estimated genome size of 2.3 Gb, and easy culture in lab conditions. We constructed an Illumina Paired-end and 12 Mate-Pair libraries (ranging from 3 kb to 17 kb) and sequenced. The kmer-frequency analysis confirmed the estimated genome size of 2.3 Gb and the genome assembly was performed by using ALLPATHS-LG. So far, the assembly reached scaffold N50 of 2.2 Mb (including gaps) and total scaffold length of 2.1 Gb. RNA-seq data from various tissues will be used to construct gene models and evaluate the assembly.