Soybean genome sequenced

The full genome for soyabean, one of the world's most important economic crops, has been sequenced by scientists in the U.S., revealing a few surprises and opening up the potential to develop improved strains.

The researchers estimate that soybean (Glycine max) has a 1.1 gigabase genome and approximately 46,430 genes, which is 70 per cent more than Arabidopsis and more than twice as many as humans.

The researchers were surprised to find that most of these genes - around 78 per cent - occur around the ends of the chromosomes, where most of the recombination also takes place, while over half of the genomic sequence occurs in repeat-rich, low-recombination heterochromatic regions surrounding the centromeres.

Soybean also appears to have a highly duplicated genome, with around three quarters of the genes copied in multiple locations. This is the result of genome duplications that took place approximately 59 and 13 million years ago, after which the genome underwent gene diversification and loss and numerous chromosome rearrangements.

The genome was sequenced using a whole genome shotgun approach and integrated with physical, high density genetic maps. Soybean is the first legume and the largest plant genome to be sequenced.

Most of the sequencing was performed at the Joint Genome Institute in Walnut Creek, California, and the team was led by Scott Jackson from the Department of Agronomy at Purdue University in Indiana, U.S..

It's expected that the publishing of the complete soybean genome will aid in a deeper understanding of the plant, including some valuable traits, such as its ability to fix nitrogen in the soil via a symbiotic relationship with soil bacteria.

The genome will also aid in the development of new lines of soybean, including one with a reduced level of stachyose, which will be more easily digested by humans and other animals. Another low phytate strain could reduce the environmental impact of runoff from swine and poultry waste.

A gene that lends resistance to the devastating Asian soybean rust (ASR) has also been identified, which could lead to new strains with enhanced resistance to the disease.

The soybean genome will also serve as a vital reference for the other 20,000-odd legume species.

The genome was published in Nature today.