In a weed lurk life's secrets

December 15, 2000

The sequencing of the first plant genome will herald a new era for plant sciences, writes Mike Bevan.

On the face of it, there is little to distinguish thale cress, or Arabidopsis thaliana , from any other common garden weed. Yet this week, the species takes the limelight with the announcement that the first plant genome sequence has been completed.

This milestone in genetic research underlines Arabidopsis 's importance as a pre-eminent model for plant biology. In part, this is because thale cress can grow in many different habitats, from the Arctic to the Equator. This makes the adaptations it has developed to live in such varied circumstances of great interest to scientists. More importantly, it is convenient to grow in the laboratory and it produces huge numbers of seeds.

Five years ago, a group of scientists from Europe, Japan and the United States decided that the relatively small genome of Arabidopsis should be sequenced to increase the scope and scale of biological investigation, as has been done for yeast and the nematode worm Caenorhabditis elegans. The Arabidopsis Genome Initiative has completed this task, as well as a comprehensive initial analysis of the sequence, which is all contained in four reports in this week's issue of Nature.

The 116 million base pairs sequenced contain nearly 26,000 genes, the largest genome set analysed to date (work on the human genome has yet to progress to this stage). Scientists will be able to use this rich harvest of genes and analyses in a variety of ways. The sequence can be used to understand the functions of many previously unexplored Arabidopsis genes. Many of these genes are closely related to others in different multicellular organisms, so much can be learnt of the 250,000 other plant species by integrating studies of the numerous functions shared by plants and animals. For example, Arabidopsis and humans have in common genes involved in diseases such as cancer and premature ageing.

Furthermore, the implications of recording this first plant genome sequence stretch beyond basic science. As scientists can be expected to gain a detailed understanding of processes unique to plants -Jsuch as their complex metabolism, their interaction with their environment and how they cope with pests and diseases - the question arises as to how this information can be put to work. Although crop plants appear very different, they are as closely related as mammals are to each other. Arabidopsis genes generally perform related functions in crop plants, and the sequence of those genes on the genome is also often similar. Hence, the Arabidopsis genome can be used to identify individual genes with valuable agronomic features that can then be transferred using genetically modified technology. It can also help pick out others in crop plants that perform related functions that can be introduced into different lines via other breeding techniques.

There are many reasons why we need to know much more about how plants function. They produce all of the food - and a wide range of medicines - for humans and domestic animals. Ensuring adequate future nutrition for the growing population while reducing the environmental impact of agriculture is a challenge. Plants are key components of the biosphere, responsible for carbon dioxide reduction and oxygen generation. They provide habitats for many other organisms. The impact of rapid environmental change on crop production can be addressed by understanding how plants that are adapted to a narrow range of climates and soils can remain highly productive in more extreme conditions.

This knowledge of plant gene function is critically important for understanding the environment and ensuring food security. Plant sciences have long been the Cinderella of the life sciences, with none of the glamour and generous funding associated with biomedical research. The advances being made with Arabidopsis promise to bring plant scientists to the ball.

Mike Bevan is head of molecular genetics at the John Innes Centre in Norwich.

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