Plant ion-pump gene cloned, sequenced.

Plant ion-pump gene cloned, sequenced

Scientists for the first time have cloned and sequenced a gene for an energy-generating protein that controls a higher plant's ability to take up nutrients from soil. The research might someday allow plant breeders to genetically engineer crops that more efficiently extract essential minerals through their roots, says molecular biologist and study leader Michael R. Sussman at the University of Wisconsin-Madison.

Better nutrient-extracting crops could live in deficient soils and so need little or no added fertilizer, reducing a farmer's costs and decreasing pollution from fertilizer runoff. By isolating "the gene for this very important function that is common to all plants, [Sussman] has found a tool by which we can study one of the fundamental processes [in plant growth]," says University of Wisconsin-Madison horticulturist Warren H. Gabelman.

The gene codes for a protein that crosses the outer membrane of all plant and fungal cells and transports hydrogen ions from one side of the membrane to the other. The pump creates an electrical difference between a cell's inside and outside, producing "the most electricity of any protein in nature," Sussman says. A root cell uses this electricity to bring in soil nutrients.

Sussman and co-workers Jeffrey F. Harper and Terry K. Surrowy wanted to study the gene for the pump from a plant of the mustard family, Arabidopsis thaliana, because of this plant's short lifespan and small number of genes. They used what they knew about the protein structure of an oat plant's pump to create a short genetic probe that pinpointed a partial-length oat gene. They then used this oat gene to find an equivalent full-length gene in A. thaliana, they report in the February PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCIES (Vol. 86, No. 4).

Although researchers identified the pump gene in fungal DNA several years ago, it has proved more difficult to pick out in higher plants because the protein exists in tiny amounts.

Sussman and his research team are now trying to insert the newly identified gene into tobacco plants in a way that will cause the plants to produce an abnormally large number of proton pumps. "If we can [do this] without hurting the plant, we may be able to improve nutrient uptake [in all kinds of plants]," Sussman says. They also hope to use the gene to find its counterparts in many agricultural crops to correlate genetic variations to variations in nutrient-absorbing ability, Sussman says.