RNAi Explained
Rich Jorgensen Featured on Special NOVA Broadcast

Rich Jorgensen

Richard Jorgensen, associate professor of plant sciences at the University of Arizona and editor-in-chief of The Plant Cell, was featured in the NOVA-scienceNOW program “RNAi Explained,” which aired on PBS on July 26, 2005. The 15-minute program can be viewed online at http://www.pbs.org/wgbh/nova/sciencenow/3210/02.html.

NOVA-scienceNOW airs five times a year and covers “breaking science stories, science and politics, and science and culture,” according to host Robert Krulwich. In “RNAi Explained,” Krulwich tells the story of this powerful discovery that could lead to cures for a seemingly endless number of human diseases, including Alzheimer’s, arthritis, cancer, HIV, muscular dystrophy, and influenza, to name just a few. He describes how RNAi (RNA interference) was a puzzle that first appeared in petunia plants in experiments conducted by Jorgensen in 1986, when he was attempting to create an intensely purple petunia flower in his work for a biotech startup company. Jorgensen explains how he inserted extra copies of a gene for purple pigment (the gene encoding the enzyme chalcone synthase) into petunia plants, expecting to get deeper purple flowers, but to his surprise found that the plants produced white flowers completely lacking in pigmentation. Jorgensen, along with Eric Lander of the Broad Institute and Massachusetts Institute of Technology and Greg Hannon of Cold Spring Harbor Laboratory, describes how it took another decade to work out the mystery of the white petunias.

The secret of RNAi lies in the ability of living cells to recognize abnormal RNA and destroy it. It is believed to have evolved as an antiviral mechanism that allows cells to recognize viral RNA and degrade it, preventing the virus from becoming established inside the cell. Unbeknown to Jorgensen at the time, the gene that he inserted into his petunias produced RNA transcripts that folded into a structure recognized by the cell’s RNAi machinery as “virus,” and all copies of the gene transcript were destroyed, leaving the plants unable to make any purple pigment and resulting in white flowers.

Lander explained how scientists now can make use of RNAi to turn off any gene at will just based on knowing its DNA sequence. This ability has great potential for investigating gene function and curing disease. RNAi therapy has been used successfully in mice to treat Huntington’s disease, Lou Gehrig’s disease, hepatitis, and breast cancer. The program highlights a successful clinical trial involving RNAi in a woman with age-related macular degeneration. Lander concludes that “any sort of disease that you can imagine is fair game” as a candidate for RNAi therapy. And it all started with Rich Jorgensen’s white petunias.

Nan Eckardt
neckardt@aspb.org

Energizing Plant Biology
Chris Somerville Speaks on Future of Biofuels in U.S.

Miscanthus x giganteus (Elephantgrass) crop growing in southern Germany. From Scurlock, J.M.O. (1998). Miscanthus: a review of European experience with a novel energy crop. ORNL/TM-13732. Oak Ridge National Laboratory, Oak Ridge, Tennessee. http://bioenergy.ornl.gov/reports/miscanthus/toc.html.

ASPB member Chris Somerville delivered the keynote address at the 16th International Conference on Arabidopsis Research in Madison on June 15, 2005, during which he spoke on the importance of research and development in plant biology in the area of biomass energy.

Somerville, director of the Carnegie Institution of Washington, Department of Plant Biology at Stanford University, delivered an eloquent and inspiring message advocating a wider view of plant biology as an important source of energy, and not only agricultural commodities. The U.S. ethanol industry is one of the fastest growing energy industries in the world. Somerville cited a recent USDA–DOE study that estimated that planting biofuel crops on existing available (fallow) cropland could contribute more than 100 billion gallons of liquid fuels each year in the United States. However, he noted that grain crops such as maize are not the best suited for biomass production, owing to a substantial requirement for inputs from fossil fuels. Certain undomesticated perennial species, such as Miscanthus x giganteus (Elephantgrass) and Panicum virgatum (Switchgrass), have far greater potential as biomass energy crops. These species require minimal inputs and also have significantly higher net energy outputs than conventional grain ethanol crops.

Grain ethanol crops will continue to be the primary focus of the biomass energy industry over the next 20 years or so, but in the longer term we will see a shift to the development and use of more efficient perennial biomass crops. Because these species are undomesticated, there is great potential for their improvement as biofuel crops and a need for research in basic plant biology to improve our understanding of plant growth and development related to biomass production. Biomass crops have not yet been subjected to selection, and in addition, most breeding of crop plants has been focused on minimizing biomass and maximizing seed yield. Somerville argued that basic discoveries in plant biology will enable increased biomass production through rational improvement of many different aspects of plant growth and development, ranging from stress tolerance and disease resistance to fundamental changes in developmental processes.

“Plant biomass is basically polysaccharides and lignin,” said Somerville, indicating that basic research in these areas is of particular importance because many useful changes can be envisioned in the chemical composition of biomass. He stated that significant increases in biomass yield were possible because plants “have the capacity to increase photosynthesis if we unlock the key to growth.” Arabidopsis has become a powerful tool for basic research in plant biology, and it is increasingly clear that much of what is learned from studying this small weed is directly applicable to other species. A view of plant biology as having a significant impact on improving our ability to develop renewable sources of energy should pave the way for increased federal funding for plant biology research. “Legislators often view the big problem in agriculture as overproduction and do not see the point of further investments in basic research that might cause more overproduction,” Somer-ville lamented, concluding that “in the developed world, a more relevant social context for basic research in plant biology is energy.” He asserted that basic research on plants supports both the food and energy uses of plants. However, because the importance of plants as sources of energy is poorly understood by comparison with food uses, the community of plant biologists can play an important role in increasing public awareness of the opportunity to develop sustainable and renewable sources of energy from plants.

Nan Eckardt
neckardt@aspb.org