Sci. Aging Knowl. Environ., 8 January 2003
Extra longevity gene might boost plant fecundity
Key Words: methylation acetylation histone deacetylase chromatin
SAN FRANCISCO, CALIFORNIA--A gene that helps worms and yeast persist might also make plants robust, according to work presented here 17 December 2002 at the American Society for Cell Biology meeting. Although preliminary, this line of study could reveal whether plants age in the same way that animals do.
The small weed Arabidopsis thaliana thrives for between 8 and 10 weeks, at which point it generates seeds and dies soon after it produces its last one. Its sudden demise does not resemble the slow degeneration of most animals, which gradually lose functions over time. Researchers have wondered whether plants age at all, and if so, how similar the process is to that in yeast, worms, and mammals (see "Perennially Young?"). In those organisms, alterations in chromosome structure appear to influence aging. For example, an extra dose of a protein called Sir2--which influences how tightly DNA winds around its associated proteins--extends the life of yeast and worms. Meghan Sharp and Daphne Preuss, plant biologists at the University of Chicago, investigated whether the plant version of SIR2 influences Arabidopsis life-span.
To address the question, the scientists bestowed an extra copy of the SIR2 gene on Arabidopsis. The researchers are still figuring out whether the additional gene hikes the amount of Sir2 protein or, because of the peculiarities of plant genetics, reduces it. Nevertheless, Sharp and Preuss noticed that the manipulation alters the organism's physiology. Plants with an extra SIR2 gene lived the same amount of time as normal plants did, but they bloomed earlier, grew taller, and produced more seeds early in life. The team has yet to determine whether the plants maintain these benefits until they die, or if they just mature unusually rapidly. So far, for example, the researchers have measured seed yield and plant size only at an early time point. "The normal plants might catch up," says Preuss. "We don't know yet." Although many details remain unknown, the researchers have established that the observations arise from the extra SIR2 gene and not because the genetic manipulation alters other genes' activities; SIR2 landed at different chromosomal sites in multiple plants--yet it reprogrammed their physiology in the same way.
Although the extra SIR2 gene doesn't extend the weed's life-span, the researchers are hunting for genes that, when mutated, would have that effect. So far, they have found long-lived plants that develop late or are sterile, but they're searching for a healthy, normally reproducing plant that persists extra-long. The team hopes that such plants will help them discern similarities in aging between plants and animals and also identify features unique to plants.
SIR2's effect on seed yield and plant size is "interesting and worthy of further investigation," says plant biologist Z. Jeffrey Chen of Texas A&M University in College Station. Genetic interventions that increase seed yield are "very rare," he says, and no one knows exactly how seed generation works: "If that's easy, we don't have to work so hard to improve crop yields." And with additional study, research into Sir2's effect on plants might also bear more fruit on the topic of aging.
M. M. Sharp and D. Preuss, Chromatin modulation and gene regulation during aging and development in Arabidopsis. American Society for Cell Biology, 42nd Annual Meeting, 14 to 18 December 2002, San Francisco, California. [Meeting Home Page]
January 8, 2003 Citation: M. Beckman, Seedy Weed. Science's SAGE KE (8 January 2003), http://sageke.sciencemag.org/cgi/content/full/sageke;2003/1/nw6
Science of Aging Knowledge Environment. ISSN 1539-6150