Genetics / Today the genome of the Arabidopsis thaliana plant will be published
by Tamara Traubman
One of the most important scientific operations conducted in recent years has come to an end: scientists will publish today for the first time the complete genome of a plant. The plant looks like a small grass and its name is Arabidopsis thaliana. Unlike some of its relatives - the cabbage, cauliflower and broccoli - it has not received much public attention. But in recent years it has been used by biologists in understanding some of the most basic life mechanisms in plants and animals, including humans.
Some of the scientists involved in the project said that the decoding of the Arabidopsis genome will affect humanity more than the decoding of the human genome. This is because it will be decisively beneficial for the development of new crops that will help alleviate the plight of hunger and malnutrition in the third world.
The project - in which scientists from universities in Europe, Japan and the USA take part - lasted four years. In the process, the scientists identified the sequence of the plant's DNA units. The DNA units are made of chemical bases, and are arranged along the genome in different combinations. In those combinations of the DNA units are written recipes for the production of proteins, which carry out all the biological operations of the organism.
"Our great enthusiasm for the completion of the decoding of the Arabidopsis genome," says Dr. Dani Chaimovitz from Tel Aviv University and one of the pioneers in the study of Arabidopsis in Israel, "is due to the fact that the discoveries we derive from it have huge implications for biology as a whole."
Arabidopsis serves as what scientists call a "model plant", that is, a plant that is easy to study, and the discoveries in it are valid to a significant extent for other plants and animals as well.
Arabidopsis is easy to study because its life cycle is fast and its genome is relatively small. But almost all the genes in it also exist in other plants, so instead of trying to identify genes in plants like citrus trees - which have huge genomes and take a long time to grow - it is easier to identify them and their role in a tiny plant like Arabidopsis.
Prof. Yossi Shilo, from the Sackler Faculty of Medicine at Tel Aviv University, says that the interpretation has direct implications for medical research. "For me, as a human geneticist", he says, "this thing is a tremendous lever for medical research and for promoting the study of the human genome".
It has already happened in the past, that biologists who studied Arabidopsis, and who identified genes and characterized their function, helped biologists who studied the human genome to discover that mutations in those genes are responsible for the development of diseases.
Thus, for example, Dr. Chaimovitz and his colleagues discovered a group of genes in Arabidopsis called CFN responsible for regulating plant development in response to exposure to light. It was recently discovered that this group of genes also exists in humans, and new clues from animal experiments raise the possibility that genes from the group influence the human body's response to light, the development of cancer and mental retardation.
"As of today, the entire genome of Arabidopsis is available online to all of humanity, because it is being deciphered by institutions funded by public funds. In my opinion, this is a huge milestone", believes Prof. Yossi Hirschberg, a prominent geneticist in the field of plant genetics research from the Hebrew University.
Scientists are also interested in understanding how Arabidopsis was able to adapt to so many different climatic environments - its growing areas extend from the North Pole to the equator (in Israel it grows in Hermon).
Hirschberg says that if the researchers succeed in finding out which genes give Arabidopsis its resistance, they will be able to transplant them by genetic engineering also into crops - which have lost the traits that made them resistant in the breeding process - and create crops that are resistant to pests and diseases.
During the deciphering, the geneticists were surprised to find that Arabidopsis has more genes than the nematode worm or the fruit fly. "If you take into account that a fly, which is an animal with a brain and the ability to learn and move, only has about 13,000 genes, then it's amazing," says Prof. Hirschberg. "This means that plants are more complex than we thought."
The explanation for this, says Prof. Hirschberg, is that when plants are cold, or they are attacked, they cannot get up and run away, so during evolution they developed sophisticated defense and control mechanisms. Some of the clues to the changes that the plant went through in the distant past are still present in its genome. Now, with the completion of the decoding of the genome, it will be possible to understand the genetic changes the plant has undergone, and thus to better understand the evolution of life on Earth.
"This is today one of the most accurate and complete genomes we have," said Dr. Michael Bowen, one of the British partners in the project, at a press conference. The researchers did a thorough process of what is known as "interpreting" the genome, in which, based on the genes already known and with the help of computer software, they estimate the total number of genes and their function. But much work still remains to find out and characterize the exact roles of each of the genes.
At the end of the article detailing the researchers' findings - published today in the scientific journal "Nature" - they note that the twentieth century began with the recognition of the discoveries of the Czech monk Mendel, who studied fragrant pea plants in the monastery garden and discovered the principles of heredity. The century ends today, with the disclosure of the complete genome of a model plant, Arabidopsis.
{Appeared in Haaretz newspaper, 14/12/2000}
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