Regulation of ammonia homeostasis by the ammonium transporter AmtA in Dictyostelium discoideum

Ryuji Yoshino, Takahiro Morio, Yoko Yamada, Hidekazu Kuwayama, Masazumi Sameshima, Yoshimasa Tanaka, Hiromi Sesaki, Miho Iijima

Research output: Contribution to journalArticlepeer-review

Abstract

Ammonia has been shown to function as a morphogen at multiple steps during the development of the cellular slime mold Dictyostelium discoideum; however, it is largely unknown how intracellular ammonia levels are controlled. In the Dictyostelium genome, there are five genes that encode putative ammonium transporters: amtA, amtB, amtC, rhgA, and rhgB. Here, we show that AmtA regulates ammonia homeostasis during growth and development. We found that cells lacking amtA had increased levels of ammonia/ammonium, whereas their extracellular ammonia/ammonium levels were highly decreased. These results suggest that AmtA mediates the excretion of ammonium. In support of a role for AmtA in ammonia homeostasis, AmtA mRNA is expressed throughout the life cycle, and its expression level increases during development. Importantly, AmtA-mediated ammonia homeostasis is critical for many developmental processes. amtA- cells are more sensitive to NH4Cl than wild-type cells in inhibition of Chemotaxis toward cyclic AMP and of formation of multicellular aggregates. Furthermore, even in the absence of exogenously added ammonia, we found that amtA- cells produced many small fruiting bodies and that the viability and germination of amtA- spores were dramatically compromised. Taken together, our data clearly demonstrate that AmtA regulates ammonia homeostasis and plays important roles in multiple developmental processes in Dictyostelium.

Original languageEnglish (US)
Pages (from-to)2419-2428
Number of pages10
JournalEukaryotic Cell
Volume6
Issue number12
DOIs
StatePublished - Dec 2007

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology

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