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Eukaryotic Cell, April 2004, p. 359-368, Vol. 3, No. 2
1535-9778/04/$08.00+0     DOI: 10.1128/EC.3.2.359-368.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Novel P-Type ATPases Mediate High-Affinity Potassium or Sodium Uptake in Fungi

Begoña Benito,1 Blanca Garciadeblás,1 Peter Schreier,2 and Alonso Rodríguez-Navarro1*

Departamento de Biotecnología, Universidad Politécnica de Madrid, 28040 Madrid, Spain,1 Bayer CropScience R-TRF, 40789 Monheim, Germany2

Received 11 November 2003/ Accepted 9 February 2004

Fungi have an absolute requirement for K+, but K+ may be partially replaced by Na+. Na+ uptake in Ustilago maydis and Pichia sorbitophila was found to exhibit a fast rate, low Km, and apparent independence of the membrane potential. Searches of sequences with similarity to P-type ATPases in databases allowed us to identify three genes in these species, Umacu1, Umacu2, and PsACU1, that could encode P-type ATPases of a novel type. Deletion of the acu1 and acu2 genes proved that they encoded the transporters that mediated the high-affinity Na+ uptake of U. maydis. Heterologous expressions of the Umacu2 gene in K+ transport mutants of Saccharomyces cerevisiae and transport studies in the single and double {Delta}acu1 and {Delta}acu2 mutants of U. maydis revealed that the acu1 and acu2 genes encode transporters that mediated high-affinity K+ uptake in addition to Na+ uptake. Other fungi also have genes or pseudogenes whose translated sequences show high similarity to the ACU proteins of U. maydis and P. sorbitophila. In the phylogenetic tree of P-type ATPases all the identified ACU ATPases define a new cluster, which shows the lowest divergence with type IIC, animal Na+,K+-ATPases. The fungal high-affinity Na+ uptake mediated by ACU ATPases is functionally identical to the uptake that is mediated by some plant HKT transporters.

* Corresponding author. Mailing address: Departamento de Biotecnología, Escuela Técnica Superior de Ingenieros Agrónomos, 28040 Madrid, Spain. Phone: (34) 913365751. Fax: (34) 913365757. E-mail: arodrignavar{at}bit.etsia.upm.es.

Eukaryotic Cell, April 2004, p. 359-368, Vol. 3, No. 2
1535-9778/04/$08.00+0     DOI: 10.1128/EC.3.2.359-368.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.



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