The Physcomitrella patens has a high tolerance of drought Photo: Pirex/Wikipedia

Research into a variety of moss may hold the key to discovering traits to potentially modify crops for drought tolerance.  The moss, Physcomitrella patens, which grows on recently exposed shorelines, has the ability to survive dehydration and re-grow once watered.

Scientists from the UK University of Leeds, along with colleagues from Germany, Japan and the US, plan to explore the moss’ genome sequence and determine which genetic traits allow its survival in arid conditions. By sequencing DNA, they hope to identify which genes control these survival tactics, which could then potentially be used in crops.

"Physcomitrella is a really useful plant to study," explains Dr Cuming, who worked on the project. "By sequencing the genome, we can start to identify their genetic basis and use the knowledge for crop improvement. It's easy to transfer a moss gene into a flowering plant, and the first indications are that yes, you can enhance drought tolerance in crop species using moss genes."

Dr Ralph Quatrano of Washington University, one of the scientists who originally proposed the moss genome project, emphasises the potential for crop development. "Unlike vascular plant systems, we can target and delete specific moss genes to study their function in important crop processes, and replace them with genes from crop plants to allow us to study the evolution of gene function,” he says.

The moss holds similarities to floating algae, which prospered on earth 400 million years ago. The algae, although only one cell thick, adapted to cold, heat and drought despite being without roots or complex leaves. Similar elements of resilience found in the modern-day moss are valuable for scientists, who view Physcomitrella as a model organism due to its easy manipulation when examining plant gene function. It also possesses a single haploid genome, rather than a double from male and female parents, which allows scientists to identify which characteristics link to which gene, and is the first bryophyte to be sequenced.

Researchers from more than 40 institutions conclude that Physcomitrella harbours nearly 500 million nucleotides and up to 36, 000 genes, boasting 50% more than estimated in the human genome. The moss is also able to integrate new DNA into a defined target in its genome, unlike most plants which integrate new DNA randomly. “If we can discover what mechanisms cause the Physcomitrella genome to integrate DNA in this way we may be able to transfer those to other plants, to allow more controlled modification of their genomes," Dr Cuming explains.

However, he also stresses that some crops may already harbour the capacity seen in the moss. "We believe many of the useful genes in Physcomitrella are probably still present in 'higher' crop plants, but are no longer active in the same way,” he says. “So rather than adding new DNA, we'll just be activating what's already there to create the properties we want."

Physcomitrella is particularly useful as it provides a link between water-based algae Chlamydomonas and flowering land plants. The draft genome sequence is likely to develop further as scientists use annotation, assigning specific functions to the genes through
experiments, and analogies with related genes in other organisms.

The sequencing was carried out at the Joint Genome Institute in Berkeley, California. Findings were published on Science Express.
By Rebecca Debens

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