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Open AccessArticle

Characterization of a Functional Role of the Bradyrhizobium japonicum Isocitrate Lyase in Desiccation Tolerance

1
Department of Biology, University of Texas, Arlington, TX 76019, USA
2
Department of Soil, Water & Climate, and The BioTechnology Institute, University of Minnesota, St. Paul, MN 55108, USA
3
Division of Biotechnology, College of Environmental and Bioresource Sciences, Chonbuk National University, Iksan 570-752, Korea
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Author to whom correspondence should be addressed.
Academic Editor: Jan Schirawski
Int. J. Mol. Sci. 2015, 16(7), 16695-16709; https://doi.org/10.3390/ijms160716695
Received: 28 June 2015 / Revised: 14 July 2015 / Accepted: 20 July 2015 / Published: 22 July 2015
(This article belongs to the Section Biochemistry)
Bradyrhizobium japonicum is a nitrogen-fixing symbiont of soybean. In previous studies, transcriptomic profiling of B. japonicum USDA110, grown under various environmental conditions, revealed the highly induced gene aceA, encoding isocitrate lyase (ICL). The ICL catalyzes the conversion of isocitrate to succinate and glyoxylate in the glyoxylate bypass of the TCA cycle. Here, we evaluated the functional role of B. japonicum ICL under desiccation-induced stress conditions. We purified AceA (molecular mass = 65 kDa) from B. japonicum USDA110, using a His-tag and Ni-NTA column approach, and confirmed its ICL enzyme activity. The aceA mutant showed higher sensitivity to desiccation stress (27% relative humidity (RH)), compared to the wild type. ICL activity of the wild type strain increased approximately 2.5-fold upon exposure to 27% RH for 24 h. The aceA mutant also showed an increased susceptibility to salt stress. Gene expression analysis of aceA using qRT-PCR revealed a 148-fold induction by desiccation, while other genes involved in the glyoxylate pathway were not differentially expressed in this condition. Transcriptome analyses revealed that stress-related genes, such as chaperones, were upregulated in the wild-type under desiccating conditions, even though fold induction was not dramatic (ca. 1.5–2.5-fold). View Full-Text
Keywords: symbiotic nitrogen fixation; Bradyrhizobium japonicum; isocitrate lyase (ICL); aceA; desiccation stress symbiotic nitrogen fixation; Bradyrhizobium japonicum; isocitrate lyase (ICL); aceA; desiccation stress
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Jeon, J.-M.; Lee, H.-I.; Sadowsky, M.J.; Sugawara, M.; Chang, W.-S. Characterization of a Functional Role of the Bradyrhizobium japonicum Isocitrate Lyase in Desiccation Tolerance. Int. J. Mol. Sci. 2015, 16, 16695-16709.

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