The conserved and divergent roles of carbonic anhydrases in the filamentous fungi <i>Aspergillus fumigatus</i> and <i>Aspergillus nidulans</i>

다국어 초록 (Multilingual Abstract)

<P>Summary</P><P>Carbon dioxide (CO<SUB>2</SUB>) and its hydration product bicarbonate (HCO<SUB>3</SUB><SUP>-</SUP>) are essential molecules in various physiological processes of all living organisms. The reversible interconversion between CO<SUB>2</SUB> and HCO<SUB>3</SUB><SUP>-</SUP> is in equilibrium. This reaction is slow without catalyst, but can be rapidly facilitated by Zn<SUP>2+</SUP>-metalloenzymes named carbonic anhydrases (CAs). To gain an insight into the function of multiple clades of fungal CA, we chose to investigate the filamentous fungi <I>Aspergillus fumigatus</I> and <I>A. nidulans</I>. We identified four and two CAs in <I>A. fumigatus</I> and <I>A. nidulans</I>, respectively, named <I>cafA-D</I> and <I>canA-B</I>. The <I>cafA</I> and <I>cafB</I> genes are constitutively, strongly expressed whereas <I>cafC</I> and <I>cafD</I> genes are weakly expressed but CO<SUB>2</SUB>-inducible. Heterologous expression of the <I>A. fumigatus cafB</I>, and <I>A. nidulans canA</I> and <I>canB</I> genes completely rescued the high CO<SUB>2</SUB>-requiring phenotype of a <I>Saccharomyces cerevisiae</I>&Dgr;<I>nce103</I> mutant. Only the &Dgr;<I>cafA</I>&Dgr;<I>cafB</I> and &Dgr;<I>canB</I> deletion mutants were unable to grow at 0.033% CO<SUB>2</SUB>, of which growth defects can be restored by high CO<SUB>2</SUB>. Defects in the CAs can affect <I>Aspergilli</I> conidiation. Furthermore, <I>A. fumigatus</I>&Dgr;<I>cafA</I>, &Dgr;<I>cafB</I>, &Dgr;<I>cafC</I>, &Dgr;<I>cafD</I> and &Dgr;<I>cafA</I>&Dgr;<I>cafB</I> mutant strains are fully virulent in a low-dose murine infection.</P>