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PLANTS INTERACTING WITH OTHER ORGANISMS

Physiological Roles of Glutathione S-Transferases in Soybean Root Nodules^{1,[C],[W],[OA]}

Biology Department, Reed College, Portland, Oregon 97202 (D.A.D., C.B., Z.T., A.L., H.J.K., L.J.); and Donald Danforth Plant Science Center, St. Louis, Missouri 63132 (M.G., R.E.F., C.G.T.)

Glutathione S-transferases (GSTs) are ubiquitous enzymes that catalyze the conjugation of toxic xenobiotics and oxidatively produced compounds to reduced glutathione, which facilitates their metabolism, sequestration, or removal. We report here that soybean (Glycine max) root nodules contain at least 14 forms of GST, with GST9 being most prevalent, as measured by both real-time reverse transcription-polymerase chain reaction and identification of peptides in glutathione-affinity purified extracts. GST8 was prevalent in stems and uninfected roots, whereas GST2/10 prevailed in leaves. Purified, recombinant GSTs were shown to have wide-ranging kinetic properties, suggesting that the suite of GSTs could provide physiological flexibility to deal with numerous stresses. Levels of GST9 increased with aging, suggesting a role related to senescence. RNA interference studies of nodules on composite plants showed that a down-regulation of GST9 led to a decrease in nitrogenase (acetylene reduction) activity and an increase in oxidatively damaged proteins. These findings indicate that GSTs are abundant in nodules and likely function to provide antioxidant defenses that are critical to support nitrogen fixation.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: David A. Dalton (david.dalton{at}reed.edu).

^[C] Some figures in this article are displayed in color online but in black and white in the print edition.

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www.plantphysiol.org/cgi/doi/10.1104/pp.109.136630

^* Corresponding author; e-mail david.dalton{at}reed.edu.

Received February 3, 2009; accepted March 8, 2009; published March 11, 2009.