Analysis of a novel calcium auxotrophy in Aspergillus nidulans.
In Aspergillus nidulans a combination of null mutations in halA, encoding a protein kinase, and sltA, encoding a zinc-finger transcription factor having no yeast homologues, results in an elevated calcium requirement ('calcium auxotrophy') without impairing net calcium uptake. sltA(-) (+/-halA(-)) mutations result in hypertrophy of the vacuolar system. In halA(-)sltA(-) (and sltA(-)) strains, transcript levels for pmcA and pmcB, encoding vacuolar Ca(2+)-ATPase homologues, are highly elevated, suggesting a regulatory relationship between vacuolar membrane area and certain vacuolar membrane ATPase levels. Deletion of both pmcA and pmcB strongly suppresses the 'calcium auxotrophy'. Therefore the 'calcium auxotrophy' possibly results from excessive vacuolar calcium sequestration, causing cytosolic calcium deprivation. Null mutations in nhaA, homologous to Saccharomyces cerevisiae NHA1, encoding a plasma membrane Na(+)/H(+) antiporter effluxing Na(+) and K(+), and a non-null mutation in trkB, homologous to S. cerevisiae TRK1, encoding a plasma membrane high affinity K(+) transporter, also suppress the calcium auxotrophy.
Findon
Helen
H
Department of Microbiology, Imperial College London, Flowers Building, Armstrong Road, London SW7 2AZ, United Kingdom.
Calcagno-Pizarelli
Ana-Maria
AM
Martínez
José L
JL
Spielvogel
Anja
A
Markina-Iñarrairaegui
Ane
A
Indrakumar
Tanya
T
Ramos
José
J
Peñalva
Miguel A
MA
Espeso
Eduardo A
EA
Arst
Herbert N
HN
D001233:Aspergillus nidulans / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000235:genetics; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism; D014617:Vacuoles / Q000235:genetics / Q000378:metabolism; D016335:Zinc Fingers / Q000235:genetics
D026901:Membrane Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D025262:Vacuolar Proton-Translocating ATPases; D002118:Calcium