A mutation in the Neurospora crassa actin gene results in multiple defects in tip growth and branching

Virag, Aleksandra; Griffiths, Anthony John

doi:10.1016/j.fgb.2003.10.010

Cited by 68 publications

(53 citation statements)

References 52 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The use of the actin-destabilizing drug CA caused a misdistribution of nuclei similar to what had been observed with actin (act-1) mutants of Neurospora (36). In the present study, treatment with subinhibitory concentrations of CA reduced elongation rate and nuclear displacement rate drastically but did not cause a major change in the relationship between nuclear displacement and hyphal elongation.…”

supporting

confidence: 85%

Cytoplasmic Bulk Flow Propels Nuclei in Mature Hyphae of Neurospora crassa

et al. 2009

View full text Add to dashboard Cite

We used confocal microscopy to evaluate nuclear dynamics in mature, growing hyphae of Neurospora crassa whose nuclei expressed histone H1-tagged green fluorescent protein (GFP). In addition to the H1-GFP wild-type (WT) strain, we examined nuclear displacement (passive transport) in four mutants deficient in microtubule-related motor proteins (ro-1, ro-3, kin-1, and a ro-1 kin-1 double mutant). We also treated the WT strain with benomyl and cytochalasin A to disrupt microtubules and actin microfilaments, respectively. We found that the degree of nuclear displacement in the subapical regions of all strains correlated with hyphal elongation rate. The WT strain and that the ro-1 kin-1 double mutant showed the highest correlation between nuclear movement and hyphal elongation. Although most nuclei seemed to move forward passively, presumably carried by the cytoplasmic bulk flow, a small proportion of the movement detected was either retrograde or accelerated anterograde. The absence of a specific microtubule motor in the mutants ro-1, ro-3, or kin-1 did not prevent the anterograde and retrograde migration of nuclei; however, in the ro-1 kin-1 double mutant retrograde migration was absent. In the WT strain, almost all nuclei were elongated, whereas in all other strains a majority of nuclei were nearly spherical. With only one exception, a sizable exclusion zone was maintained between the apex and the leading nucleus. The ro-1 mutant showed the largest nucleus exclusion zone; only the treatment with cytochalasin A abolished the exclusion zone. In conclusion, the movement and distribution of nuclei in mature hyphae appear to be determined by a combination of forces, with cytoplasmic bulk flow being a major determinant. Motor proteins probably play an active role in powering the retrograde or accelerated anterograde migrations of nuclei and may also contribute to passive anterograde displacement by binding nuclei to microtubules.Organelle movement and positioning are important aspects of cell growth and differentiation (19,20,27,35). Movement and positioning of nuclei are especially important because of their implications in mitotic divisions during hyphal growth and asexual sporulation (conidiation), as well as fertilization events leading to meiosis and ascospore formation during sexual development (1,3,33). In yeast, nuclei move comparatively short distances (20, 32), whereas in filamentous fungi nuclei are typically transported over long distances within hyphae (1,34,35).Movement of nuclei in fungal cells may be either an active or a passive process. Early studies of filamentous fungi showed nuclei uniformly distributed along the entire hypha; they appeared to move with the growing hyphal apex, keeping a more or less constant distance from the cell tip. Such evidence pointed to passive displacement of nuclei by cytoplasmic bulk flow (10-12, 24), a role confirmed in our recent study on the dynamics of the microtubular cytoskeleton (28) and supported by studies with injected lipid droplets (17). Upon the discovery of m...

show abstract

supporting

confidence: 85%

Cytoplasmic Bulk Flow Propels Nuclei in Mature Hyphae of Neurospora crassa

et al. 2009

View full text Add to dashboard Cite

show abstract

“…F-actin has been demonstrated to play important roles in cell polarity regulation, septation, exocytosis, endocytosis, and organelle movement in fungi (6,7,27,40,42,64,65,73). Three F-actin-containing structures are found in fungi: actin patches that are associated with endocytic vesicles (3,7,31,72); actin cables that are assembled at sites of growth, where they form tracks for secretion and organelle transport (7,8,18,19,31,47,60,61); and contractile actomyosin rings that are involved in septum formation (7,27,33,40).…”

Section: Discussionmentioning

confidence: 99%

Nuclear Dynamics, Mitosis, and the Cytoskeleton during the Early Stages of Colony Initiation in Neurospora crassa

et al. 2010

View full text Add to dashboard Cite

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.

show abstract

“…Similarly, viable mutations in the formin SepA in A. nidulans show tip splitting (Sharpless and Harris, 2002). In Neurospora crassa, several mutants are known that lead to hyphal tip splitting (Sone and Griffiths, 1999;Bok et al, 2001;Seiler and Plamann, 2003;Virag and Griffiths, 2004). It was suggested that a calcium gradient controls the transport of vesicles.…”

Section: Regulation Of Tip Splitting By Agbni1pmentioning

confidence: 99%

From Function to Shape: A Novel Role of a Formin in Morphogenesis of the FungusAshbya gossypii

Schmitz

Kaufmann

Köhli

et al. 2006

MBoC

View full text Add to dashboard Cite

Morphogenesis of filamentous ascomycetes includes continuously elongating hyphae, frequently emerging lateral branches, and, under certain circumstances, symmetrically dividing hyphal tips. We identified the formin AgBni1p of the model fungus Ashbya gossypii as an essential factor in these processes. AgBni1p is an essential protein apparently lacking functional overlaps with the two additional A. gossypii formins that are nonessential. Agbni1 null mutants fail to develop hyphae and instead expand to potato-shaped giant cells, which lack actin cables and thus tip-directed transport of secretory vesicles. Consistent with the essential role in hyphal development, AgBni1p locates to tips, but not to septa. The presence of a diaphanous autoregulatory domain (DAD) indicates that the activation of AgBni1p depends on Rho-type GTPases. Deletion of this domain, which should render AgBni1p constitutively active, completely changes the branching pattern of young hyphae. New axes of polarity are no longer established subapically (lateral branching) but by symmetric divisions of hyphal tips (tip splitting). In wild-type hyphae, tip splitting is induced much later and only at much higher elongation speed. When GTP-locked Rho-type GTPases were tested, only the young hyphae with mutated AgCdc42p split at their tips, similar to the DAD deletion mutant. Two-hybrid experiments confirmed that AgBni1p interacts with GTP-bound AgCdc42p. These data suggest a pathway for transforming one axis into two new axes of polar growth, in which an increased activation of AgBni1p by a pulse of activated AgCdc42p stimulates additional actin cable formation and tip-directed vesicle transport, thus enlarging and ultimately splitting the polarity site.

show abstract

A mutation in the Neurospora crassa actin gene results in multiple defects in tip growth and branching

Cited by 68 publications

References 52 publications

Cytoplasmic Bulk Flow Propels Nuclei in Mature Hyphae of Neurospora crassa

Cytoplasmic Bulk Flow Propels Nuclei in Mature Hyphae of Neurospora crassa

Nuclear Dynamics, Mitosis, and the Cytoskeleton during the Early Stages of Colony Initiation in Neurospora crassa

From Function to Shape: A Novel Role of a Formin in Morphogenesis of the FungusAshbya gossypii

Contact Info

Product

Resources

About