OSU helps decode strawberry genome in bid to improve fruit

December 26, 2010
Todd Mockler
Todd Mockler, a plant molecular biologist at OSU, holds a slide containing a DNA sample. (Photo by Lynn Ketchum.)

CORVALLIS, Ore. – Researchers at Oregon State University have helped sequence the genome of a wild strawberry, laying the groundwork for genetic improvements to related fruits like apples, peaches and pears.

The advance was published online today by the journal Nature Genetics.

"This will accelerate research that will lead to improved crops, particularly commercial strawberries," said OSU plant molecular biologist Todd Mockler, one of the lead researchers. "It could lead to fruit that resists pests, smells better, tolerates heat, requires less fertilizer, has a longer shelf life, tastes better or has an improved appearance."

An international team of more than 70 researchers, 13 of whom are at OSU, identified 34,809 genes on the seven chromosomes in the woodland strawberry known as Fragaria vesca.

They chose the diminutive perennial because it's commonly used in research, is easy to breed, grows quickly and has a small genome. Additionally, it shares a substantial number of genes with apples, peaches, cherries, plums, and commercially cultivated strawberries – a crop that generated $12.9 million in gross sales for Oregon's farmers in 2009, according to a report by the OSU Extension Service.

As part of their findings, the scientists identified genes that they think might be responsible for some of the berry's characteristics like flavor, aroma, nutritional value, flowering time and response to disease. Knowing what individual genes do will allow researchers to breed crops for those specific traits. And in the case of tree fruits, they won't have to wait years to see if those traits actually show up in the fruit. For example, with molecular breeding they would be able to cross a high-yielding pear tree with one that resists a certain fungal disease, and they'd be certain that the desired genes are actually present.

The woodland strawberry is the smallest plant genome to be sequenced other than Arabidopsis thaliana, a small flowering plant in the mustard family, because it has only about 210 million base pairs, Mockler said. Base pairs are the molecules known as adenine, cytosine, guanine and thymine that form a double-stranded DNA helix.

In addition to Mockler, the OSU part of the research was led by Pankaj Jaiswal, Aaron Liston, Sushma Naithani and Nahla Bassil, a plant geneticist with the U.S. Department of Agriculture who holds a courtesy appointment at OSU. Jaiswal's lab assigned functions to about two-thirds of the strawberry's genes. Liston compared the chromosomal locations of 389 genes that the strawberry shares with peaches and found support for the hypothesis that the rose family originally had nine chromosomes. Naithani's lab predicted biochemical functions for various genes, and Liston and Bassil helped assemble the genome for the strawberry's chloroplasts, an organelle that makes sugar and starches through photosynthesis.

The strawberry work is just the latest advance in a series of genome sequencing projects at OSU. In collaboration with experts in other states, Mockler's lab is assembling the genome for the endangered snow leopard in a conservation effort aimed at improving captive breeding programs in zoos and restoring its numbers. His lab is also working with Bassil to sequence the genomes of three more kinds of strawberries as well as various varieties of apples, cherries, peaches, blueberries and black raspberries.

Mockler’s lab is also sequencing the genomes of eight hazelnut varieties, a South American carnivorous plant known as Genlisea aurea, and duckweed, a tiny plant that looks like pond scum and may have potential as a source of biofuel.

Meanwhile, Liston is sequencing the genome for milkweed, and Jaiswal, who helped create a database of plant genomes, is trying to find genes that control flowering time in rice and corn.

Mockler was part of a global team that sequenced the genome of the wild grass Brachypodium distachyon, which scientists hope will serve as a model for improving some grass and cereal crops.

Author: Tiffany Woods
Source: Todd Mockler