November 19, 2012, Shenzhen, China An international research team led by Nanjing Agricultural University and BGI, has completed the first genomic sequence of pear by an approach using the combination of BAC-by-BAC strategy and next-gen sequencing. The pear genome not only provides an invaluable new resource for breeding improvement of this important crop, but also sheds new light on the genome evolution and other genome-wide comparative studies. The results were published online in Genome Research.
As one of the oldest fruit crops, pear has more than 3,000 years of cultivation history and is likely to have originated during the Tertiary period (65 million years ago) in southwestern China. This important fruit crop is genetically diverse with more than 5,000 cultivars and accessions present all over the world that could be divided into two major groups, the European or "Occidental" pears and the Asiatic or "Oriental" pears.
Unlike many crops, pear is known to be highly heterozygous, which is a big challenge for de novo assembly based on current strategies. In this study, researchers sequenced and assembled the pear genome, P. bretschneideri Rehd. cv. Dangshansuli using a combination of BAC-by-BAC and next generation sequencing technology. This approach is developed by BGI, which can be used to study the genomes with high level of heterozygosity and/or repetitive sequences. After data process, the assembled pear genome size is about 512.0 Mb, with a total of 42,812 protein-coding genes.
In this study, researchers identified repetitive sequences of 271.9 Mb, accounting for 53.1% of the pear genome. By comparison with the apple genome, they found the size differences between pear and apple genome were mostly contributed by content diversity in transposable elements (TEs), while genic regions are similar in both species.
Through comparative genomics and evolution analysis, researchers found pear, apple and strawberry shared an ancient whole
|Contact: Jia Liu|