I. Symbiosis between nitrogen fixing bacteria and legumes
II. Function and regulation of Sinorhizobium nodulation genes
III. Plant genes and cell response in nitrogen-fixing symbiosis
Part I: Symbiosis between nitrogen fixing bacteria and legumes
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Legume plants form specialized root nodules to host "rhizobia", nitrogen-fixing bacterial symbionts. Rhizobia hosting legumes are able to grow without exogenous nitrogen fertilizer allowing them to be high in protein and to provide nutrition to surrounding plants. In part 1 of her talk, Long gives an overview rhizobium-legume symbiosis including infection and nodule formation and the chemical signals exchanged between the plant and the bacteria.
In Part 2. Long goes into more detail on how chemicals released from legumes increase transcription of specific bacterial genes required for plant infection, while in Part 3 she describes how bacterial factors induce production of specific proteins by the plant. By using a custom gene chip, Long can follow the regulation of both Sinorhizobium genes and alfalfa genes at the same time, during nodule formation. This has allowed her to show that this is an extremely complex process with the expression of hundreds of plant and bacterial genes changing during this process.
Sharon Long received her undergraduate degree from California Institute of Technology and her doctorate from Yale University. She has been a professor of Biological Sciences at Stanford University since 1982 and she was Dean of the School of Humanities and Sciences from 2001-2007.
In her research, Dr. Long employs a spectrum of approaches including microbial and plant biology, biochemistry and genetics to study the symbiosis of nitrogen-fixing Rhizobium bacteria and their plant hosts. Her work is directly relevant to both agricultural productivity and energy conservation.
Dr. Long has received numerous awards and honors during her career. She is a member of the National Academy of Sciences, the American Academy of Arts and Sciences, and the American Philosophical Society.
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- Gibson KE, Kobayashi H, Walker GC. 2008. Molecular determinants of a symbiotic chronic infection. Annu Rev Genet. 42:413-41.
- Giles E.D. Oldroyd and J. Allan Downie. 2008. Coordinating Nodule Morphogenesis with Rhizobial Infection in Legumes. Annual Review of Plant Biology 59: 519-546.
- Keith Roberts. 2007. Handbook of Plant Science, Volume 1.