Ultrastructure of mitosis in the cowpea rust fungus Uromyces phaseoli var. Vignae.

Abstract

Aspects of the ultrastructure of mitotic nuclei of the fungus Uromyces phaseoli var. vignae are described from both intercellular hyphae in the cowpea host and infection structures induced to differentiate in vitro. The interphase nucleusassociated organelle (NAO) consists of two trilamellar acircular disks connected by an osmiophilic bar. The intranuclear spindle develops between these disks when they separate. The spindle contains pole to pole, interdigitating, chromosomal, and fragmentary microtubules arranged to form a central bundle along the surface of which lie the metaphase chromosomes. No metaphase plate is found. There are up to three microtubules per kinetochore and approximately 14 chromosomes on the haploid spindle. Telophase elongation appears to involve extension of pole to pole microtubules with no evidence for the remaining presence of interdigitating microtubules. Concomitantly, numerous cytoplasmic microtubules develop from each NAO disk where few or none are present in other phases. Reformation of the interphase NAO involves the formation of a sausage-shaped intermediate at late telophase. The nuclear envelope remains intact and the nucleolus persists throughout division. Various aspects of the spindle and NAOs appear to be evolutionary intermediates between Ascomycetes and higher Basidiomycetes, thus supporting the theory of Basidiomycete evolution from the former group and demonstrating an encouraging correlation between mitotic characteristics and other phylogenetic markers.

Validation of RT-qPCR reference genes for in planta expression studies in Hemileia vastatrix, the causal agent of coffee leaf rust

“…In vitro growth Fresh uredospores (30 mg) of the Hemileia vastatrix isolate CIFC 1065 (race II) were spread in sterile distilled water in Petri dishes to germinate (GU e germinated uredospores sample) or on artificial oil-collodion membranes (Heath & Heath 1976) placed in Petri dishes to differentiate appressoria (A) , and incubated under saturating humidity for 24 h under darkness at 24 C. Fungal material (aprox. 15 mg) was collected by filtration (for the GU sample) or the oil-collodion membranes were used directly for grinding (for the A sample).…”

Mechanics of chromosome separation during mitosis in Fusarium (Fungi imperfecti): new evidence from ultrastructural and laser microbeam experiments.

“…It would certainly seem to be a possibility for the numerous other situations where both astral microtubules and a distinct anaphase-telophase elongation of the central spindle occur . Included in this group are numerous fungi (10,16,17,(48)(49)(50)(51)(52)(53)(54)(55)(56)(57), several slime molds (58)(59)(60), some algae (61,62), certain protozoans (45,63), and higher animals (1, 2, 9, 11) . Girbardt's concept (10) of mitosis in the Basidiomycete, Trametes versicolor, is especially concordant .…”

“…The astral microtubules are inferred to play a role in the deployment of these putative polar forces because they are attached to the SPB and increase in number and length at an appropriate time (10,16,18) . In addition, they seem to play a role in migration of interphase nuclei, which apparently involves a force transmitted to the SPB (18,26,(29)(30)(31).…”

Mitosis and the phylogeny of Taphrina

“…The exceptional species are very similar to reported heterobasidiomycetous yeasts (as listed in Heath 1978Heath , 1980Taylor and Wells 1979). In general terms, the rust spindles (described in most detail by Heath and Heath 1976and Harder 1976a, 1976b are much larger than those of Taphrina; they have a much more pronounced and coherent central spindle, many more spindle microtubules, larger and more clearly condensed chromosomes, larger NAOs, and longer metaphase spindles. Rust NAOs duplicate at late telophase, via a morphologically distinct intermediate, and are therefore double throughout interphase.…”

“…Heath and Heath (1976) demonstrated the potential of mitotic analysis to help explain relationships among hypothetically primitive basidiomycetes by showing that the cowpea rust fungus has a mitotic apparatus which shares characteristics with those of some ascomvcetes. An obvious extension of this approach, also suggested by Kubai (1978), is to analyse the mitotic apparatus of members of the genus Taphrina, since Savile (1955) has already argued that they represent the extant group most likely to resemble a common ancestor of the ascomycetes and basidiomycetes.…”