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Applied and Environmental Microbiology, November 2009, p. 6777-6782, Vol. 75, No. 21
0099-2240/09/$08.00+0     doi:10.1128/AEM.00708-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Negative Roles of a Novel Nitrogen Metabolite Repression-Related Gene, TAR1, in Laccase Production and Nitrate Utilization by the Basidiomycete Cryptococcus neoformans{triangledown}

Nan Jiang,1 Dongguang Xiao,2 Defa Zhang,1 Naiyu Sun,1 Bing Yan,1 and Xudong Zhu1*

State Key Program of Microbiology and Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China,1 Tianjin Industry Microbiology Key Lab, College of Bioengineering, Tianjin University of Science and Technology, Tianjin 300457, China2

Received 26 March 2009/ Accepted 29 August 2009

The multicopper oxidase laccase is widespread in fungi and has great industrial importance. One puzzle regarding laccase production in the basidiomycetous yeast Cryptococcus neoformans is that it is inhibited by high temperature (e.g., 37°C). In this paper, we report identification of a nitrogen metabolite repression-related gene, TAR1, which is responsible for laccase repression. Disruption of TAR1 results in a significant increase in the level of LAC1 mRNA at 37°C. The putative protein Tar1 shares a moderate level of similarity with the nitrogen metabolite repressors Nmr1 and NmrA from Neurospora crassa and Aspergillus nidulans, respectively. Likewise, Tar1 has a negative role in the utilization of nitrate. Furthermore, the structure of Tar1 is unique. Tar1 lacks the long C-terminal region of Nmr1 and NmrA. It contains the canonical Rossmann fold motif, GlyXXGlyXXGly, whereas Nmr1 and NmrA have variable residues at the Gly positions. Interestingly, the promoter region of TAR1 contains three TTC/GAA repeats which are likely the heat shock factor (Hsf) binding sites, implying that Hsf has a role in laccase inhibition. TAR1 mediation of temperature-associated repression of LAC1 suggests a novel mechanism of laccase regulation and a new function for Nmr proteins. Our work may be helpful for industry in terms of promotion of laccase activity.

* Corresponding author. Mailing address: Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, People's Republic of China. Phone and fax: 86 (22) 23505723. E-mail: xudong82{at}nankai.edu.cn

{triangledown} Published ahead of print on 4 September 2009.

Applied and Environmental Microbiology, November 2009, p. 6777-6782, Vol. 75, No. 21
0099-2240/09/$08.00+0     doi:10.1128/AEM.00708-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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