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FRIDAY, June 27, 2003 (HealthDayNews) -- In experiments with plants, researchers have discovered a mechanism by which auxin, an important plant growth hormone, moves into cells.
The finding could have important implications in making chemotherapy more effective, the researchers believe, because proteins similar to human multidrug resistant (MDR) proteins control this movement.
Lead researcher Angus Murphy, an assistant professor of horticulture at Purdue University, says that auxin has a lot to do with the shape of a plant and also controls how plants bend in response to light and gravity.
Although the proteins that transport auxin from cell to cell in plants have been identified, how they work has remained a mystery, Murphy says.
"We found that one group of proteins controls the movement of auxin," he explains. Murphy and his colleagues discovered that plant proteins, similar to human MDR proteins, become depleted, allowing auxin to move into cells. The findings appear in the June 26 issue of Nature.
In humans, MDR proteins protect cells from toxins and are the proteins responsible for removing chemotherapy drugs from cells. To bypass MDR proteins, chemotherapy doses need to be high, causing the severe side effects associated with the treatment.
The latest finding has direct implications in agriculture and horticulture, by allowing for the regulation of plant growth. Using these findings, plant size, bushiness, fruit production and root structure can be manipulated, Murphy says.
But the discovery also might lead to ways to control and restrict human MDR proteins, making lower doses of chemotherapy more effective with fewer side effects, he adds.
Northeastern University biology professor Kim Lewis says the finding that genetic manipulation of hormones can affect a plant's growth rate, intensity of growth and root system growth is very interesting.
"What I am less enthusiastic about is the possible connection to human multidrug resistant cancer," Lewis says. "There are a number of molecules that work directly against human MDR proteins that have already been identified. Adding yet another member to this already large family of proteins will be not be helpful."
Lewis also disputes the claim that the finding will help in understanding the function of human MDR proteins. "The function of human MDR proteins is well understood," he notes.