Washington, DC, May 18, 2014 — Dr. Zhu Yu-Xian at School of Life Sciences and collaborators sequenced the genome of a cultivated cotton Gossypiumarboreum(cotton A-genome). The results were published online in Nature Genetics as a research article entitled “Genome sequence of the cultivated cotton Gossypiumarboreum”.

G. arboreum, known as the “tree cotton”, is originated from the tropical and subtropical regions of Asia and a “parent” of Gossypiumhirsutum, the most cultivated species of cotton in the world.The A-genome sequenced by Dr. Zhu and collaboratorsis 1700 mega bases in length, containing 41330 protein-coding genes. Most of the genome (68.5%) is composed of repetitive DNA sequence, which is the highest ratio ever found in sequenced eudicots. Comparing with the G. raimondii genome (cotton D-genome), which was sequenced by the same research team in 2012, the cotton A-genome maintains high similarity at both gene and synteny level. After a speciation event dated about 5 million years ago (2-13 MYA), the A-genome has gone through multiple massive retrotransposition activities and the genomes size is thusly twice as long as the D-genome.Using comparative transcriptomics and functional genomics, Dr. Zhu leading his research team showed thatthe signal molecule ethylene plays dualroles in cotton genomes. The over-production of ethylene in D-genome suppresses cotton fiber development, while in A-genome the deficiency of ethylene is responsible for short fiber length. The disease-resistant gene (R genes) families are significantly expanded in D-genome and contracted in A-genome, by contrast with the close sib cocao.Only the expanded genes in D-genome can be active by Verticilliuminfection, practically resulting in the lose-of-resistance of A-genome.

These results will help breeders address increasing threats to cotton by tapping into the plant’s genetic variability for productivity, fiber quality, and tolerance and resistance to pests and diseases. The achievement is also a milestone that will make it much easier to sequence the more genetically complex upland cotton, the basis of most modern commercial cotton varieties.

Ph.D. student Li Qin from Dr. Zhu’s lab is the co-first author of the paper. Project partners include researchers from the Chinese Academy of Agricultural Sciences (CAAS), Cotton Research Institute, Anyang, China; BGI, Shenzhen, China and the Crop Germplasm Research Unit, Southern Plains Agricultural Research Center, USDA-ARS. This work was supported by the National Basic Research Program of Cotton Research of China, the National Natural Science Foundation of China and the State Key Laboratory of Protein and Plant Gene Research.

Edited by: Zhang Jiang

Source: School of Life Sciences