For anyone tethered to a lawnmower, the Holy Grail of horticultural accomplishment would be grass that never grows but is always green.
Now, that vision of suburban bliss seems plausible; scientists have mapped a critical hormone signaling pathway that regulates the stature of plants. In addition to lawns that rarely require mowing, the finding could also enable the development of sturdier, more fruitful crop plants such as rice, wheat, soybeans, and corn.
In a paper published in the journal Nature, Howard Hughes Medical Institute scientists report they have deciphered the signaling pathway for a key class of steroid hormones that regulates growth and development in plants.
"By manipulating the steroid pathwaywe think we can regulate plant stature and yield," said Joanne Chory, a Howard Hughes Medical Institute investigator at the Salk Institute for Biological Studies, and the senior author of the new report.
Manipulation of plant stature has been a longstanding goal in horticulture, agronomy, and forestry. The ability to control plant size precisely would have broad implications for everything from urban forestry to crop and garden plant development.
Beyond perpetually short grass, trees could be made more compact for better growth in crowded cities, and berry bushes could be made taller for ease of harvesting.
To chart the pathway, Chory and colleague Grgory Vert of the Salk Institute's Plant Biology Laboratory examined the molecular influence of a family of plant hormones known as brassinosteroids. Scientists have found brassinosteroids in all plants where they have looked for them.
As critical chemical messengers of plant development, they are found in low levels in virtually all plant cells, including seeds, flowers, roots, leaves, stems, pollen, and young vegetative tissue.
"Without them, plants are tiny dwarves, with reduced vasculature and roots, and are infertile," Chory explained. "They also regulate senescence or aging. Since brassinosteroids mainly regulate cell expansion, though, they are one of the most important hormones that regulate stature."
Knowing the molecular chain of command -- how the hormone acts to influence genetic events that govern development at the cellular level -- gives scientists a way to reshape the steroid pathway to develop plants that grow in specified ways.
"We might be able to dwarf grass and keep it green by limiting brassinosteroids or increase the yield of rice by having more brassinosteroids in seeds," Chory said. Another recent study by Makoto Matsuoka's group in Japan, she said, showed that limiting brassinosteroids in rice affected leaf angle and improved yield in densely planted fields.
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