Scientists Studying Pathways that Control Plant Growth

Scientists from the USDA ARS Sustainable Agricultural Systems Laboratory and the Canadian Research Council are analyzing the cellular machinery that controls the growth rate, longevity, nutrition uptake, and metabolism of experimental plants via the "TOR signaling" pathway. The TOR (target of rapamycin) pathway is a nutrition-and-energy sensor that plays a major role in mediating the signals that control growth, development, and lifespan in yeast, animals, and humans.

Previous studies showed that in yeast, mice and humans, rapamycin functions by binding to a protein known as "FKBP12" (FK506 binding protein 12), but does not bind effectively to FKBP12-related proteins in the model plant Arabidopsis or in other plants, possibly because of differences in protein structure. The research team then developed transgenic Arabidopsis plants that produced the yeast version of the FKBP12 protein and selected lines for treatment with rapamycin to monitor the plants' responses at the growth, developmental, metabolic, and gene-expression levels.

The plants with the yeast FKBP12 gene responded to rapamycin by growing more slowly, producing shorter roots and shoots and living longer than their normal counterparts. They also observed that rapamycin treatments also affected gene expression, turning off or "down-regulating" genes associated with photosynthesis and cell growth. Consequently, rapamycin-treated transgenic plants failed to respond to increased light and displayed growth rates 10 times slower than those of nonengineered plants when lighting was intensified.

For more details about this research, read the article published in the October 2013 issue of Agricultural Research magazine at http://www.ars.usda.gov/is/AR/archive/oct13/plants1013.htm.