Molecular identity and heterogeneity of Trichomonad parasites in a closed avian population.

Columbids (pigeons and doves) are the primary host of Trichomonas gallinae, the flagellate protozoon which causes avian trichomoniasis, a widespread, often lethal disease. Although predominantly apathogenic, the organism is paradigmatic for the study of strain-specific virulence, with some strains causing greater than 75% mortality and epizootic die-offs in wildlife populations. In recent years, research on this important emerging pathogen has been neglected and genetic variation within the parasite has not hitherto been investigated.

The pot1+ homologue in Aspergillus nidulans is required for ordering mitotic events.

Orderly progression through mitosis is essential to reduce segregation errors in the cell's genetic material. We have used a cytological screen to identify a mutant that progresses through mitosis aberrantly and have cloned the complementing gene, nimU, which encodes a protein related to Pot1 and other telomere end-binding proteins. We show that loss of nimU function leads to premature mitotic spindle elongation, premature mitotic exit, errors in chromosome segregation, and failure to delay mitotic exit under conditions that normally evoke the mitotic spindle checkpoint response.

Dynamic distribution of BIMG(PP1) in living hyphae of Aspergillus indicates a novel role in septum formation.

Mutation of bimG, the major protein phosphatase 1 gene in Aspergillus nidulans, causes multiple cell cycle and hyphal growth defects that are associated with overphosphorylation of subcellular components. We have used functional translational fusions with the green fluorescent protein (GFP) to show that BIMG has at least four discrete locations within growing hyphae. Three of these locations, the hyphal tip, the spindle pole body and the nucleus, correlate with previously known requirements for bimG(PP1) in mitosis and hyphal growth and are highly dynamic.

A type 2A protein phosphatase gene from Aspergillus nidulans is involved in hyphal morphogenesis.

A PCR-based approach, using degenerate oligonucleotide primers, was used to isolate fragments of two genes encoding type 2A protein phosphatases from the filamentous fungus, Aspergillus nidulans. The complete genomic sequence of one of these genes, pphA, was isolated and characterised. The pphA gene was predicted to encode a 329-residue protein which is about 85% identical to mammalian protein phosphatase 2A.

The expression of D-cyclin genes defines distinct developmental zones in snapdragon apical meristems and is locally regulated by the Cycloidea gene.

Three D-cyclin genes are expressed in the apical meristems of snapdragon (Antirrhinum majus). The cyclin D1 and D3b genes are expressed throughout meristems, whereas cyclin D3a is restricted to the peripheral region of the meristem, especially the organ primordia. During floral development, cyclin D3b expression is: (a) locally modulated in the cells immediately surrounding the base of organ primordia, defining a zone between lateral organs that may act as a developmental boundary; (b) locally modulated in the ventral petals during petal folding; and (c) is specifically repressed in the dorsal stamen by the cycloidea gene.

sodVIC is an alpha-COP-related gene which is essential for establishing and maintaining polarized growth in Aspergillus nidulans.

Strains of Aspergillus nidulans carrying the conditional-lethal mutation sodVIC1 (stabilization of disomy) are defective in nuclear division and hyphal extension. The mutation affects both the establishment and maintenance of polar growth, since mutant spores do not germinate at restrictive temperature and preexisting hyphae stop growing upon upshift. The defect is reversible within the first 3-4 h at restrictive temperature but longer periods of incubation are lethal due to cell lysis and morphological abnormalities.

A temperature-sensitive splicing mutation in the bimG gene of Aspergillus produces an N-terminal fragment which interferes with type 1 protein phosphatase function.

Progression through anaphase requires high levels of type 1 protein phosphatase (PP1) activity in a variety of eukaryotes, including Aspergillus nidulans. A conditional lethal, temperature-sensitive mutant in one of the Aspergillus PP1 genes, bimG, prevents the normal completion of anaphase when cells are grown at restrictive temperature and this has been shown to be due to a reduction in type 1 phosphatase activity. We show that the bimG11 allele is recessive to the wild-type allele in heterozygous diploids, implying that the mutation is due to loss of function at restrictive temperature, but molecular disruption of the wild-type bimG gene shows that the gene is not essential and has no discernable phenotype under laboratory conditions.

Distinct classes of cdc2-related genes are differentially expressed during the cell division cycle in plants.

cdc2 and several related genes encode the catalytic subunits of cyclin-dependent kinases, which have been implicated in a number of cellular processes, including control of cell division. As a first step in exploring their function in plants, we isolated four cdc2-related genes from Antirrhinum. Two genes, cdc2a and cdc2b, encode proteins that contain a perfectly conserved PSTAIRE motif characteristic of cdc2 homologs, whereas the products of the two remaining genes, cdc2c and cdc2d, appear to represent a new subclass of proteins that have so far only been identified in plants.

Fungal pathogens of oat roots and tomato leaves employ closely related enzymes to detoxify different host plant saponins.

Antifungal saponins are produced by many plants and have been implicated as preformed determinants of resistance to fungal attack. The importance of saponin detoxification in fungal pathogenesis has recently been demonstrated for the fungus Gaeumannomyces graminis var. avenae, which produces the enzyme avenacinase.

A novel Arabidopsis type 1 protein phosphatase is highly expressed in male and female tissues and functionally complements a conditional cell cycle mutant of Aspergillus.

Type 1 protein phosphatases are very highly conserved throughout eukaryotes where they regulate a number of key metabolic and morphogenetic processes. A cDNA, AtPP1bg, representing a new member of the type 1 protein phosphatase gene family in Arabidopsis has been isolated on the basis of hybridization with the Aspergillus bimG protein phosphatase gene. The AtPP1bg gene potentially encodes a 37 kDa protein very closely related to PP1 but with divergent N- and C-termini.

Host range of a plant pathogenic fungus determined by a saponin detoxifying enzyme.

Antifungal saponins occur in many plant species and may provide a preformed chemical barrier to attack by phytopathogenic fungi. Some fungal pathogens can enzymatically detoxify host plant saponins, which suggests that saponin detoxification may determine the host range of these fungi. A gene encoding a saponin detoxifying enzyme was cloned from the cereal-infecting fungus Gaeumannomyces graminis.

Analysis of the genetic variability of maize streak virus.

The nucleotide sequences of the small intergenic region (SIR) and the gene encoding the coat protein of 12 maize streak virus (MSV) isolates from different geographic locations have been determined. These have been used to assess the variability of the virus and to construct evolutionary dendrograms. For the viruses analyzed, the maximum levels of sequence divergence were found to be 10.

Rapid production of full-length, infectious geminivirus clones by abutting primer PCR (AbP-PCR).

The application of the polymerase chain reaction (PCR) method of DNA amplification for the isolation of full-length, infectious clones of geminiviruses is described. Non-overlapping, abutting 20-mer oligonucleotide primers were used to produce a linear product from the circular geminivirus genomic template. Clones of African cassava mosaic virus (ACMV) DNA A, obtained by this method, were infectious following mechanical inoculation (in the presence of ACMV DNA B) onto Nicotiana benthamiana.

The nucleotide sequence of an infectious insect-transmissible clone of the geminivirus Panicum streak virus.

The infectious genome of a Kenyan isolate of Panicum streak virus (PSV) has been cloned and sequenced. Infection of host plants was done using an Agrobacterium binary vector containing a partial repeat of the genome. Progeny virus from resultant infections proved to be transmissible by the leafhopper Cicadulina mbila (Naude).