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Fungi use the SakA (HogA) pathway for phytochrome-dependent light signalling


Stress-sensing in fungi depends on a signalling cascade comprised of a two-component phosphorylation relay plus a subsequent MAP kinase cascade to trigger gene expression. Besides osmotic or oxidative stress, fungi sense many other environmental factors, one of which is light1,2. Light controls morphogenetic pathways but also the production of secondary metabolites such as penicillin. Here we show that phytochrome-dependent light signalling in Aspergillus nidulans involves the stress-sensing and osmosensing signalling pathway. In a screening for ‘blind’ mutants, the MAP kinase SakA (also known as HogA) was identified by whole-genome sequencing. The phytochrome FphA physically interacted with the histidine-containing phosphotransfer protein YpdA and caused light-dependent phosphorylation of the MAP kinase SakA and its shuttling into nuclei. In the absence of phytochrome, SakA still responded to osmotic stress but not to light. The SakA pathway thus integrates several stress factors and can be considered to be a hub for environmental signals.

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Figure 1: Isolation of an A. nidulans ‘blind’ mutant.
Figure 2: Impact of the SakA signalling pathway on light sensing.
Figure 3: Phytochrome interacts with the histidine-containing phophotransfer protein YpdA.
Figure 4: SakA shuttling and phosphorylation after light exposure.


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This work was supported by the German Science Foundation (DFG, FOR 1334). Z.Y. was supported by the China Scholarship Council (CSC). We thank E. Wohlmann and B. Schreckenberger for technical assistance and great help with immunostaining. We also would like to thank J. Hübner and C. Streng for some assistance. We are extremely grateful to J. Aguirre (UNAM, Mexico City) for sending us several A. nidulans strains.

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Z.Y. planned and performed the experiments and analysed the data. O.A. was responsible for whole-genome sequencing and analysed the sequencing data. R.F. planned the experiments, analysed the data and wrote the manuscript.

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Correspondence to Reinhard Fischer.

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The authors declare no competing financial interests.

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Yu, Z., Armant, O. & Fischer, R. Fungi use the SakA (HogA) pathway for phytochrome-dependent light signalling. Nat Microbiol 1, 16019 (2016).

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