Abstract

Eucommia ulmoides is an ancient specie survived in the quaternary glacial period. As a traditional Chinese medicinal plant, Eucommia is a unique plant which contains hardy rubber around the world. Except for Hevea brasiliensis, Eucommia is one of the most potential natural rubber resources and a strategically important resource for Chinese rubber reserve. To comprehensively analyze the genomic structure, identify the key functional genes, study the origin and evolution and reveal the genetic background in E. ulmoides, we finished the whole genome fine map of E. ulmoides. We used whole genome shotgun strategy by combining the Illumina and PacBio sequencing platform to overcome the difficulty in de novo genome assembly. The results showed that Eucommia has a very complicated genome with the genome size reach up to 1.02G, heterozygosity over 1.1%, repetitive sequences reach up to 66%. The scaffold N50 is longer than 900 Kb, breaking through the bottleneck of too short scaffold N50 of complicated genome. More than 26 thousands functional genes and 3 thousands non-coding RNA were annotated in Eucommia genome. Seventy genes were identified relating to rubber biosynthesis, among which TIDS5 was considered to be the key functional gene. The upstream pathway is MVA pathway. There are 42, 11 and 13 genes related to chloregenic acid, quercetin, kaempferol and α-linolenic acid biosynthesis, respectively. A lot of adversity stress related genes were also indentified in Eucommia genome, e. g.8 kinds of heat stress related genes, 16 kinds of chilling stress related genes, 23 kinds of drought stress related genes, 61 kinds of saline-alkali stress related genes, 9 kinds of insect-resistant genes and 44 kinds of plant resistance genes. The detailed whole genome analysis will offer an important theoretical foundation for improving rubber biosynthesis, medicinal component accumulation, stress resistance and studying the mode of Eucommia sex determination, the origin and evolution of Eucommia, It will stand as a milestone in the Eucommia research history.

Keywords: Eucommia ulmoides; Rubber; Genome sequencing;Fine map; Functional gene