Two mating groups of Polysphondylium pallidum, a dictyostelid cellular slime mold

 Seven strains representative of Polysphondylium pallidum were examined in terms of mating relationship and morphology. By mating tests, two heterothallic mating groups were detected. By morphological comparisons, they were clearly different in number of branches and in shape of bases and tip cells of sorophores. These results suggested that these two mating groups were distinct taxa. Received: January 23, 2002 / Accepted: August 30, 2002 Present address:Kanagawa Prefectural Museum of Natural History, Odawara, Kanagawa, Japan (visiting researcher) Acknowledgments I thank Dr. James C. Cavender, Department of Environmental and Plant Biology, Ohio University, Athens, OH, USA, for providing the cultures of three strains, V-1, WS320, and WS543. Correspondence to:H. Hagiwara     

Polysphondylium multicystogenum sp. nov., a new dictyostelid species from Sierra Leone, West Africa

Polysphondylium multicystogenum, a new heterothallic species of dictyostelids, is described based on three isolates collected from soils in Sierra Leone, West Africa. This species is characterized by sorophores with a combination of clavate base and ovoid to oblong tip cell, smaller spores and abundant microcyst production under the usual culture conditions for sorocarp formation at 20 C. This is the first report of Polysphondylium producing such abundant microcysts.     

A microcyst-overproducing mutant of Polysphondylium pallidum

A mutant, PN6017, of the cellular slime mold Polysphondylium pallidum was selected by cell-surface labeling with a monoclonal antibody, mAb 293, and fluorescence-activated cell sorting. The antibody was directed against an L-fucose-containing epitope on glycoproteins, designated ep 293, and the mutant showed reduced and delayed expression of this epitope. PN6017 was distinguished from other mutants of this kind by extensive microcyst formation on agar plates under conditions where the wild type formed only sparse microcysts. In suspension cultures transformation of cells into microcysts was negligible in the wild type, and close to 100% in the mutant. Under these conditions microcyst formation in the mutant began at 5-7 h of starvation. At the same time expression of ep 293 and also of a developmentally regulated cytoplasmic protein, pallidin, became detectable. This coincidence in time suggests that microcyst formation in PN6017 is coupled to the same control mechanism as the two other developmentally regulated processes.     

Macrocyst genetics in Polysphondylium pallidum, a cellular slime mould.

The discovery of two mating types in the cellular slime mould Polysphondylium pallidum is reported. Two developmental mutants produced in strains of opposite mating type but which do not proceed past the aggregation stage of development are capable of producing macrocysts. These macrosysts were viable and 5 to 10% germinated after 6 weeks of storage. When the macrocyst progeny were cloned, several classes of non-parental phenotypes were recovered.     

True divergent differentiation in a cellular slime mold, Polysphondylium pallidum.

Three abstract models of divergent cell differentiation to multiple cell types are presented. These differ primarily in the proportion of developmental events common to the pathways leading to each cell type. Two experimental approaches are outlined to determine which type best describes divergent differentiation occurring in a particular organism. The first technique is to describe and compare changes in labeling of specific polypeptides which characterize development to the several cell types. The second is to observe the ability of mutants which are blocked in one pathway to develop along alternate pathways. These approaches are applied to the case of Polysphondylium pallidum, where amebae develop into stalk cells, spores, or microcysts. It is concluded that cell differentiation in P. pallidum is of the truly divergent type in which developing cells show identical sequences of events until a branch point, and thereafter very different sequences of events.     

A mutant strain of Polysphondylium pallidum deficient in production of cyclic AMP.

A mutant strain (PN507) of the cellular slime mold Polysphondylium pallidum is described which: (a) is morphogenetically abnormal in stalk formation; (b) secretes unusually low quantities of cyclic AMP; (c) responds to exogenous cyclic AMP in the same manner as wild type, by differentiating stalk cells and synthesizing several specific proteins; (d) complements with other morphogenetic mutants secreting normal amounts of cyclic AMP to produce fruiting structures resembling wild type. The tentative conclusion is that the critical defect of PN507 is low production of cyclic AMP.     

A taxonomic revision of granite outcrop species of Minuartia (Arenaria)

Minuartia glabra (Michx.) Mattfeld andM. uniflora (Walt.) Mattfeld are proposed as the proper taxonomic treatments ofArenaria glabra Michx. [A. groenlandica var.glabra (Michx.) Fern.] andArenaria uniflora (Walt.) Muhl. respectively. A previously unreported species,Minuartia alabamensis is described as new.Minuartia alabamensis andM. uniflora axe more closely related to one another than either is toM. glabra. Minuartia glabra is postulated to be derived from the Arcto-Tertiary flora, which invaded the Piedmont from the Appalachian Highlands.Minuartia alabamensis andM. uniflora are thought to be relicts or species derived from the Madro-Tertiary flora, which invaded the Piedmont from the Southwestern United States and Mexican Highlands.     

Plantago ser. Sericeae, a taxonomic revision

Plantago ser. Sericeae Rahn belongs to subgen. Psyllium (Juss.) Harms sect. Gnaphaloides Barn. It is distributed in the mountains from Mexico along the Andes to Argentina. Seven species are recognized: P. nivea H. B. K., P. tolucensis Pilger, P. linearis H. B. K., P. lamprophylla Pilger, P. grandiflora Meyen, P. bismarckii Niederlein, and P. sericea H. B. K., the last with 7 subspecies and 3 varieties.     

Isolation,Purification, and Properties of Lytic Enzyme from Polysphondylium pallidum Myxamoebae

Two lytic enzymes (enzyme I and enzyme II) that lysed Micrococcus lysodeikticus were isolated from the crude extract of Polysphondylium pallidum myxamoebae grown in the presence of Klebsiella aerogenes by precipitation with protamine sulfate and by chromatography on DEAE-Sepharose CL-6B. Enzyme I was further purified by gel filtration on a Superose12 column, and enzyme II by chromatography on a MonoQ HR 5/5 column and gel filtration on a Superose12 column. Enzyme I was a basic protein, while enzyme II was acidic. The molecular weights of enzyme I and II were about 14,000 and 22,000, respectively by SDS-polyacrylamide gel electrophoresis. Optimum pHs for the activity were 5.0 for enzyme I and between 3.5 and 4.0 for enzyme II. The maximum activity of enzyme I and II was obtained at 65°C and 45°C to 55°C and at ionic strength of 0.0075 to 0.03 and 0.06, respectively. Both enzymes cleaved the glycosidic bond of β(1,4)-N-acetylmuramyl-acetylglucosamine of the cell wall peptidoglycan of Micrococcus lysodeikticus. These results indicate that the two lytic enzymes of Polysphondylium pallidum myxamoebae are N-acetylmuramidases.     

A taxonomic revision of Secale (Triticeae, Poaceae)

Several taxa have previously been recognized within Secale , but most of them are difficult or even impossible to distinguish morphologically. We recognize only three species: S. sylvestre, S. strictum , and S. cereale. Secale strictum has priority over S. montanum and has two subspecies, ssp. strictum and ssp. africanum , and two varieties within ssp. strictum , van strictum and var. ciliatoglume comb. nov. Secale cereale is also treated as having two subspecies. The cultivated taxa, marked by their tough rachises, are placed in ssp. cereale and the wild or weedy taxa that have more or less fragile rachis, in ssp. ancestrale. A complete synonymy is given for S. cereale , but typification has been omitted because, in many instances, type material does not exist or has been impossible to trace.     

A new species ofFontanesia (Oleaceae) from China and taxonomic revision of the genus

Fontanesia longicarpa K.-J. Kim is newly described from China. This distinctive species is known only from the Zhejiang province and differs from other species in the genus by the size and shape of its fruit. As currently circumscribed, the genus now consists of three taxa;F. longicarpa, F. philliraeoides Labill. var.philliraeoides andF. philliraeoides var.fortunei (Carr.) Koehne. A revisionary study of the genus is provided, including a key and pertinent synonymy.     

The Breeding System of Polysphondylium pallidum,a Cellular Slime Mold*

SYNOPSIS. A mating type analysis was performed on 231 isolates of the cellular slime mold, Polysphondylium pallidum found in 61 samples collected in eastern North America between northern Florida and southern Canada. Seventy-eight percent of the isolates belonged to one of 2 mating types; 18% were incapable of mating with any partner; 3% were homothallic; and 1%, consisting of 2 isolates from a Florida sample, belonged to a separate breeding group. It is suggested that the majority of isolates represent a species capable of local genetic adaptation to a niche, the parameters of which undergo considerable variation over space and time.