Global transcriptional response of aspergillus niger to blocked active citrate export through deletion of the exporter gene

Thanaporn Laothanachareon*, Lyon Bruinsma, Bart Nijsse, Tom Schonewille, Maria Suarez-Diez, Juan Antonio Tamayo-Ramos, Vitor A.P. Martins Dos Santos, Peter J. Schaap

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Aspergillus niger is the major industrial citrate producer worldwide. Export as well as uptake of citric acid are believed to occur by active, proton-dependent, symport systems. Both are major bottlenecks for industrial citrate production. Therefore, we assessed the consequences of deleting the citT gene encoding the A. niger citrate exporter, effectively blocking active citrate export. We followed the consumption of glucose and citrate as carbon sources, monitored the secretion of organic acids and carried out a thorough transcriptome pathway enrichment analysis. Under controlled cultivation conditions that normally promote citrate secretion, the knock-out strain secreted negligible amounts of citrate. Blocking active citrate export in this way led to a reduced glucose uptake and a reduced expression of high-affinity glucose transporter genes, mstG and mstH. The glyoxylate shunt was strongly activated and an increased expression of the OAH gene was observed, resulting in a more than two-fold higher concentration of oxalate in the medium. Deletion of citT did not affect citrate uptake suggesting that citrate export and citrate uptake are uncoupled from the system.

Original languageEnglish
Article number409
JournalJournal of Fungi
Volume7
Issue number6
DOIs
Publication statusPublished - 23 May 2021

Keywords

  • CexA gene
  • Citrate exporter
  • Citric acid
  • CitT gene
  • Oxalic acid
  • Spergillus niger
  • Transcriptome

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