Eukaryotes Genomes - ARABIDOPSIS THALIANA

Arabidopsis thaliana (mouse ear cress) is a small uninteresting-looking little plant with a rosette of leaves, thin stems and small white flowers, found on the rock exposures of basalt scarps and also frequently found as a weed of gardens, cemeteries, parks and roadsides, on paths, wall-tops and in flower beds.

Arabidopsis thaliana is widely used by plant science researchers as a model organism to study plant developmental processes. It is a member of the Brassicaceae family, like cabbage and radish. Unlike those species, however, it has no major agronomic importance. A. thaliana does have many advantages in the research field, these include among others, a small genome size (a haploid content of around 100 Mbp of DNA which is distributed among five chromosomes), a rapid life cycle (about 5 weeks from seed to seed), easy cultivation in restricted space, prolific seed production, and a large number of mutant stocks that are available for researchers from a variety of stock centres.

There are many genes which are similar in all plants and the study of genes in a model organism like A. thaliana facillitates our understanding of gene expression and function in all plants. Furthermore, since animals and plants are both eukaryotes, many of the genes found in A. thaliana have homologs in animals. Arabidopsis has the smallest genome of any flowering plant, which is the main reason it was selected as a model organism for genome sequencing The DNA of Arabidopsis is made up of about 140 million bases, which are parcelled into five chromosomes.

Evolutionarily speaking, Arabidopsis is considered to be a genetic model for more than 200,000 species of flowering plants, each of which shares a basic architectural foundation and similar biochemical processes. However, it is the different versions of these genes that determine when and where a plant will grow best and how it will look. Scientists have used Arabidopsis for the past 40 years as the model for finding a gene and have used it as a guide to find equivalent genes in other plants, such as rice, corn, potatoes or tomatoes.

Researchers have already found genes in Arabidopsis thaliana that may be used to improve other crops especially due to the discovery of two weakened SHATTERPROOF genes in A. thaliana. Crops can be improved in a number of ways, and manipulating genes to improve yield is just one. Twenty to fifty percent of a rapeseed crop, harvested and crushed to yield canola oil, can be lost because the pods open and release the seeds before the farmer can harvest them. But when two genes, SHATTERPROOF1 (SHP1) and SHATTERPROOF2 (SHP2), are mutated, the seed pods fail to shatter, or burst. The ideal situation for the farmer would be to delay pod shattering until the crop has been harvested. Genes that control pod shattering in A. thaliana are likely to be present in close relatives like cauliflower, broccoli, Brussels sprouts, peas, soy beans and other important food crops. Finding weak versions of SHATTERPROOF and inserting them into rapeseed might increase the production of crop per hectare, making the land more productive and reducing the amount of water, pesticides and fertiliser a farmer needs.

References:

http://www.tigr.org/tdb/e2k1/ath1/
http://www.genomenewsnetwork.org/sequenced_genomes/genome_guide_p1.shtml
http://www.genomenewsnetwork.org/articles/04_00/shatterproof.shtml
http://plants.usda.gov/cgi_bin/plant_profile.cgi?symbol=ARTH
http://www.arabidopsis.org/