Scientists discover genetic key to growing hardier plants

A team of scientists led by Roberto Gaxiola, an assistant professor of plant science, has discovered a genetic key to generating plants that are more productive, more drought-resistant, and can grow in soils low in nutrients.

Their work is the first to successfully test in cells a 30-year-old hypothesis that explains the movement of a primary growth and development hormone through plants.

The researchers from UConn, Purdue University, and Pennsylvania State University have determined that one of three proton pumps found within plant cells, previously believed to have an extremely limited function, plays a critical role in plant root and shoot system growth and development. The proton pump controls cell division, expansion, and hormone transport. Over-expressing the single gene that encodes this particular proton pump significantly enhances the transportation of the primary plant growth hormone, auxin, and results in plants with stronger, more extensive root systems and as much as 60 percent more foliage, the researchers report in the Oct. 7 issue of Science.

“This discovery has the potential to revolutionize agriculture worldwide,” says Gaxiola. “This over-expression regulates the development of one of the most important parts of the plant, the roots. A plant with larger roots is a healthier and more productive plant because, with a larger root system, the plant is able to get water and nutrients from larger soil areas.

“Biology textbooks tell you there are three pumps inside a plant’s cell but one is less important. Our research shows that is not the case,” Gaxiola says. “As it turns out, that tiny pump is required to shuttle the master pump – the plant’s major engine – to the plasma membrane. That, in turn, allows the master pump to facilitate the transport of more of the growth hormone, auxin, through the plant’s plasma membrane and through the plant’s root and shoot systems, resulting in enhanced cell division and growth.”

All plants contain three proton pumps – a master pump, known as the P-type H+-ATPase, that facilitates transport of nutrients in and out of plant cells, and two other pumps that work within plant cells. Biologists have shown that only the P-type H+-ATPase pumps protons into the space outside the cell to create changes that drive the transport of small molecules in and out of cells.

Until now, they believed the AVP1 H+-PPase that Gaxiola’s group over-expressed merely controlled pH levels within plant vacuoles – large storage areas inside plant cells – and served primarily as a back-up pump to a larger vacuolar pump known as V-ATPase. Scientists believed that the larger vacuolar pump was the only one to help shuttle the master pump to and from the plant cell’s plasma membrane.

In collaboration with scientists at the Massachusetts Institute of Technology and Harvard University, Gaxiola previously had created plants in which the AVP1 gene was over-expressed using the research plant Arabidopsis thaliana. As Gaxiola predicted, these plants were salt- and drought-resistant and sequestered more salt ions in their vacuoles. Surprisingly the plants also had abnormally large root and shoot systems.