Actin Precedes Myosin in Formation of Contractile Rings in Aspergillus nidulans

Ref ID: 18461

Author:

Terry Hill, Loretta Jackson-Hayes, Xiao Wang

Author address:

Rhodes College, USA  

Full conference title:

11 th European Conference on Fungal Genetics

Abstract:

Cytokinesis in filamentous fungi involves the progressive inward growth of the cell wall and plasma membrane,
resulting in a series of functionally connected multinucleate compartments delimited by crosswalls termed septa.  
By screening chemically mutagenized strains of the model fungus Aspergillus nidulans, we have identified several
septation8208;impaired isolates with mutations occurring in loci different from those of previously8208;identified
Aspergillus nidulans “œsep” mutations.  Here we report that the lesion in one of these strains (RCH2) occurs in a
gene that encodes a fungal homologue of mammalian myosin8208;II (MyoB; AN4706).  Sequencing of the MyoB allele
in the RCH2 strain identifies a point mutation predicted to result in a glycine8208;to8208;aspartate amino acid substitution
at residue 843 in the myosin8208;II converter domain.  This residue is conserved in all fungal, plant, and animal myosin8208;
II sequences that we have examined.   The mutation does not prevent localization of the MyoB protein to
contractile rings, but it does block ring constriction.  Wild type MyoB colocalizes with myosin light chain (MLC;
AN6732), tropomyosin (TpmA; AN5686), and  α 8208;actinin (AcnA; AN7707) in contractile rings.  Down8208;regulation of
wild8208;type MyoB expression under control of the A. nidulans AlcA promoter blocks septation and localization of
MLC to pre8208;septal rings, but not localization of actin or TpmA.  Similarly, ring targeting of AcnA is blocked by the
RCH2 mutation.   Conversely, ring targeting of MyoB, AcnA, MLC, and TpmA are all blocked by disruption of
filamentous actin using Latrunculin B.  We propose, therefore, an “œactin8208;first” model for the relationship between
actin and myosin8208;II in formation of contractile rings.

Abstract Number: PR1.44

Conference Year: 2012

Link to conference website: http://www.ecfg.info/images/Abstract_Book_Electronic.pdf

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