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The Cysteine Protease–Cysteine Protease Inhibitor System Explored in Soybean Nodule Development
Department of Plant Production and Soil Science, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria 0002, South Africa
Department of Plant Science, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria 0002, South Africa
Biotechnology Unit School of Molecular and Life Sciences, University of Limpopo, Sovenga 0727, South Africa
Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
These authors contributed equally to this work.
* Author to whom correspondence should be addressed.
Received: 29 May 2013; in revised form: 12 July 2013 / Accepted: 22 July 2013 / Published: 20 August 2013
Abstract: Almost all protease families have been associated with plant development, particularly senescence, which is the final developmental stage of every organ before cell death. Proteolysis remobilizes and recycles nitrogen from senescent organs that is required, for example, seed development. Senescence-associated expression of proteases has recently been characterized using large-scale gene expression analysis seeking to identify and characterize senescence-related genes. Increasing activities of proteolytic enzymes, particularly cysteine proteases, are observed during the senescence of legume nodules, in which a symbiotic relationship between the host plant and bacteria (Rhizobia) facilitate the fixation of atmospheric nitrogen. It is generally considered that cysteine proteases are compartmentalized to prevent uncontrolled proteolysis in nitrogen-fixing nodules. In addition, the activities of cysteine proteases are regulated by endogenous cysteine protease inhibitors called cystatins. These small proteins form reversible complexes with cysteine proteases, leading to inactivation. However, very little is currently known about how the cysteine protease-cysteine protease inhibitor (cystatin) system is regulated during nodule development. Moreover, our current understanding of the expression and functions of proteases and protease inhibitors in nodules is fragmented. To address this issue, we have summarized the current knowledge and techniques used for studying proteases and their inhibitors including the application of “omics” tools, with a particular focus on changes in the cysteine protease-cystatin system during nodule development.
Keywords: soybean nodules; cysteine proteases; cystatins; nodule development; senescence; Glycine max
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Vorster, B.J.; Schlüter, U.; du Plessis, M.; van Wyk, S.; Makgopa, M.E.; Ncube, I.; Quain, M.D.; Kunert, K.; Foyer, C.H. The Cysteine Protease–Cysteine Protease Inhibitor System Explored in Soybean Nodule Development. Agronomy 2013, 3, 550-570.
Vorster BJ, Schlüter U, du Plessis M, van Wyk S, Makgopa ME, Ncube I, Quain MD, Kunert K, Foyer CH. The Cysteine Protease–Cysteine Protease Inhibitor System Explored in Soybean Nodule Development. Agronomy. 2013; 3(3):550-570.
Vorster, Barend J.; Schlüter, Urte; du Plessis, Magdeleen; van Wyk, Stefan; Makgopa, Matome E.; Ncube, Ignatious; Quain, Marian D.; Kunert, Karl; Foyer, Christine H. 2013. "The Cysteine Protease–Cysteine Protease Inhibitor System Explored in Soybean Nodule Development." Agronomy 3, no. 3: 550-570.