Mitogen-activated protein kinases MpkA and MpkB independently affect micafungin sensitivity in <i>Aspergillus nidulans</i>

<div><p>The transcriptional regulation of the MAPK <i>mpkA</i> and cell wall-related genes in <i>Aspergillus nidulans</i> differs from that of their counterparts in <i>Saccharomyces cerevisiae</i>. The <i>A. nidulans</i> MAPK MpkB is putatively orthologous to the yeast MAPKs Kss1p and Fus3p. To investigate MpkB and its contribution to cell wall integrity in <i>A. nidulans</i>, we constructed <i>mpkB</i>-disruptant (<i>mpkB∆</i>) strains. We previously showed that <i>mpkA</i>∆ strains exhibited reduced colony growth and increased sensitivity to the β-1,3-glucan synthase inhibitor micafungin. Like <i>mpkA</i>∆ strains, <i>mpkB∆</i> strains exhibited slight growth retardation and increased sensitivity to micafungin. Although MpkB-dependent signaling modulated the transcription of some cell wall-related genes, the sugar composition of cell wall fractions was similar among wild-type, <i>mpkA</i>∆, and <i>mpkB</i>∆ strains<i>.</i> To elucidate the relationship between MpkA and MpkB pathways, we compared conditional mutants of <i>mpkB</i> with those with <i>mpkA</i> deletion. Sensitivity testing suggested that MpkA and MpkB additively contribute to micafungin activity in <i>A. nidulans</i>.</p></div>