Nuclear dynamics, mitosis, and the cytoskeleton during the early stages of colony initiation in Neurospora crassa.
Neurospora crassa macroconidia form germ tubes that are involved in colony establishment and conidial anastomosis tubes (CATs) that fuse to form interconnected networks of conidial germlings. Nuclear and cytoskeletal behaviors were analyzed in macroconidia, germ tubes, and CATs in strains that expressed fluorescently labeled proteins. Heterokaryons formed by CAT fusion provided a rapid method for the imaging of multiple labeled fusion proteins and minimized the potential risk of overexpression artifacts. Mitosis occurred more slowly in nongerminated macroconidia (1.0 to 1.5 h) than in germ tubes (16 to 20 min). The nucleoporin SON-1 was not released from the nuclear envelope during mitosis, which suggests that N. crassa exhibits a form of "closed mitosis." During CAT homing, nuclei did not enter CATs, and mitosis was arrested. Benomyl treatment showed that CAT induction, homing, fusion, as well as nuclear migration through fused CATs do not require microtubules or mitosis. Three ropy mutants (ro-1, ro-3, and ro-11) defective in the dynein/dynactin microtubule motor were impaired in nuclear positioning, but nuclei still migrated through fused CATs. Latrunculin B treatment, imaging of F-actin in living cells using Lifeact-red fluorescent protein (RFP), and analysis of mutants defective in the Arp2/3 complex demonstrated that actin plays important roles in CAT fusion.
Roca
M Gabriela
MG
Fungal Cell Biology Group, Institute of Cell Biology, University of Edinburgh, Rutherford Building, Mayfield Road, Edinburgh EH9 3JH, United Kingdom.
Kuo
Hsiao-Che
HC
Lichius
Alexander
A
Freitag
Michael
M
Read
Nick D
ND
D000199:Actins / Q000378:metabolism; D001542:Benomyl / Q000494:pharmacology; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D015169:Colony Count, Microbial; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism*; D000072159:Dynactin Complex; D004398:Dyneins / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D008938:Mitosis / Q000187:drug effects; D008954:Models, Biological; D009068:Movement / Q000187:drug effects; D009492:Neurospora crassa / Q000166:cytology* / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D013172:Spores, Fungal / Q000166:cytology / Q000187:drug effects; D053778:Thiazolidines / Q000494:pharmacology; D013997:Time Factors
D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D000072159:Dynactin Complex; D008869:Microtubule-Associated Proteins; D053778:Thiazolidines; D049452:Green Fluorescent Proteins; D004398:Dyneins; C037068:latrunculin B; D001542:Benomyl