R&D CENTER

A new genome sequence of Populus alba x Populus tremula var. glandulosa (Salicaceae)

Jongsun Park1,2,*, Hong Xi1,2, Yongsung Kim1,2, and Mi Kwon1,2*
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Due to rapid development of sequencing and genome assembly technologies, the cost for whole genome sequencing has been dropped a lot reaching that 1,000 dollars per 1 Gbp. First genome of Populus (Populus trichocarpa) was published in 2006, as a model tree. After that, three more genomes, P. tremula, P. tremuloides, and P. tremula x P. tremuloides, were recently released. In the genome-wide association study approach, 962 individuals of P. tichocarpa has also been sequenced. One of Korean Populus species, called as Hyunsasi (Populus alba x Populus tremula var. glandulosa) was firstly breed species, which was fully adapted in our atmosphere. In addition, sterile individual of Hyunsasi has been utilized as a material for molecular studies because sterile characteristic will block modified genes to natural population. To understand this species at the genome level, we generated around 200x coverage raw data of P. alba x P. tremula var. glandulosa genome using Illumina HiSeq2000 with four different libraries. We got the first draft genome of P. alba x P. tremula var. glandulosa assembled by Platanus due to heterozygosity. Total length of this genome is 494.91 Mbp (N50 is 20,134 bp), which is largest in comparison to the other four sequenced Populus genomes. Number of ORFs predicted by AUGUSTUS is 58,395, which is similar to that of Populus tremuloides genome. 21 GATA, 27 TCP, and 133 NAC transcription factors (TFs) were identified from P. alba x P. tremula var. glandulosa genome, presenting that number of TFs of all three TF families are middle in comparison to the rest four Populus genome. 330 Cytochrome P450s (CYPs) were identified from P. alba x P. tremula var. glandulosa genome, which is second largest family among five Populus genomes. In addition, 2,225 out of 2,302 CYPs are common in the six genomes including Salix purpurea, indicating that not so many species-specific Populus CYPs exist among them. All these data can be accessed in Populus Comparative Genome Database (PGCD; http://www.populusgenome.info/), also providing diverse comparative genomics web-based tools for analyzing five genomes efficiently.