Abstract
Because of the industrial and medical importance of members of the fungal genus Aspergillus, there is considerable interest in the functions of cytoskeletal components in growth and secretion in these organisms. We have analyzed the genome of Aspergillus nidulans and found that there are two previously unstudied myosin genes, a myosin II homolog, myoB (product = MyoB) and a myosin V homolog, myoE (product = MyoE). Deletions of either cause significant growth defects. MyoB localizes in strings that coalesce into contractile rings at forming septa. It is critical for septation and normal deposition of chitin but not for hyphal extension. MyoE localizes to the Spitzenkörper and to moving puncta in the cytoplasm. Time-lapse imaging of SynA, a v-SNARE, reveals that in myoE deletion strains vesicles no longer localize to the Spitzenkörper. Tip morphology is slightly abnormal and branching occurs more frequently than in controls. Tip extension is slower than in controls, but because hyphal diameter is greater, growth (increase in volume/time) is only slightly reduced. Concentration of vesicles into the Spitzenkörper before incorporation into the plasma membrane is, thus, not required for hyphal growth but facilitates faster tip extension and a more normal hyphal shape.
Highlights
Filamentous fungi in general, and members of the genus Aspergillus in particular, are important industrially and medically
The actin cytoskeleton is essential for several critical functions in filamentous fungi including tip growth, septation, endocytosis and exocytosis [1,2,3,4,5,6,7,8,9,10]
The existence of myosin II and myosin V genes in A. nidulans has been noted previously [11,15], but no analysis of the genes nor their functions was reported and the genome database numbers for the genes were not given. To identify these genes and determine if there were additional unidentified myosin heavy chain genes, we carried out BLAST searches of the A. nidulans genome databases with multiple myosin sequences
Summary
Filamentous fungi in general, and members of the genus Aspergillus in particular, are important industrially and medically. They are important for the production of products as diverse as soy sauce, glucoamylase, a key enzyme in producing high fructose corn syrup, and anti-cholesterol drugs such as lovastatin. There are two genes in which chitin synthase sequences are fused to myosin motor domains, csmA and csmB [13,14]. The products of these genes belong to an unusual class of myosins, sometimes designated class 17 myosins [11] that is apparently restricted to fungi, Neither csmA nor csmB is essential, but null mutations of either gene cause morphological defects consistent with improper cell wall formation. Deletion of csmB and simultaneous downregulation of csmA is lethal [14]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
