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

International Journal of Molecular Sciences

Jeong-Min Jeon¹  Hae-In Lee¹  Michael J. Sadowsky²  Masayuki Sugawara²  Woo-Suk Chang¹ 

[1] Department of Biology, University of Texas, Arlington, TX 76019, USA; E-Mails:;Department of Soil, Water & Climate, and The BioTechnology Institute, University of Minnesota, St. Paul, MN 55108, USA; E-Mails:

关键词: symbiotic nitrogen fixation;    Bradyrhizobium japonicum;    isocitrate lyase (ICL);    aceA;    desiccation stress;   

DOI  :  10.3390/ijms160716695

来源: mdpi

【 摘 要 】

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. japonicumUSDA110, 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).

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.