Microbody-like organelles as taxonomic markers among oomycetes

Powell, Martha J.; Lehnen, Larry P.; Bortnick, Richard N.

doi:10.1016/0303-2647(85)90032-2

Cited by 34 publications

(17 citation statements)

References 42 publications

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“…These forms are widely regarded as a polyphyletic assemblage of uncertain relationships to "higher" fungi (4). For example, the oomycetes have traditionally been grouped with the "true" fungi but comparisons of several biochemical and morphological characteristics suggest a close relationship to xanthophytes and chrysophytes (4)(5)(6)(7). Taxonomic placement of the oomycetes is still controversial; in some schemes they are grouped with the higher fungi (8), and in others they are grouped with the chrysophytes and their relatives (9,10).…”

mentioning

confidence: 99%

Phylogenetic relationships between chlorophytes, chrysophytes, and oomycetes.

Gunderson¹,

Elwood²,

Ingold³

et al. 1987

Proc. Natl. Acad. Sci. U.S.A.

352

129

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The phylogenetic relationships among the chlorophyte Chlamydomnonas reinhardtii, the chrysophyte Ochromonas danica, and the oomycete Achlya bisexualis were explored by comparing the sequences of their small-subunit ribosomal RNA coding regions. Comparisons of similarity values or inspection of phylogenetic trees constructed by distance matrix methods reveal a very close relationship between oomycetes and chrysophytes. The separation of chrysophytes from chlorophytes is comparable to that of plants from animals, and both separations are far antedated by the divergence of a number of other protist groups.Traditional analyses based on phenotypic criteria frequently depict chlorophytes (green algae) and chrysophytes (goldenbrown algae) as representatives of lineages that diverged soon after the appearance of the earliest protists (1, 2). Comparisons of numerous characteristics such as features of nuclear division, chloroplast structure and pigment types, kinetid ultrastructure, the nature of the cell wall, and mitochondrial crista structure suggest a long and separate evolutionary history for these algal lineages. The presence of tubular mitochondrial cristae in chrysophytes and lamellar mitochondria cristae in chlorophytes (3) may be particularly significant. Since no recognizably monophyletic protistan groups are split with respect to crista type, and related groups seem to be connected by this characteristic, fundamental differences in mitochondrial structure are thought to reflect ancient divergences and to be of significance at a high taxonomic level.Certain colorless protistan lineages may be more closely related to the chrysophytes than to the chlorophytes. Among these groups are the "lower" fungi. These forms are widely regarded as a polyphyletic assemblage of uncertain relationships to "higher" fungi (4). For example, the oomycetes have traditionally been grouped with the "true" fungi but comparisons of several biochemical and morphological characteristics suggest a close relationship to xanthophytes and chrysophytes (4-7). Taxonomic placement of the oomycetes is still controversial; in some schemes they are grouped with the higher fungi (8), and in others they are grouped with the chrysophytes and their relatives (9, 10).Since there is little agreement about which phenotypic characteristics are most reliable for inferring evolutionary relationships, a consensus phylogeny for protists has never emerged. A phylogenetic tree, which reflects true genotypic similarity, can be inferred from comparisons of macromolecular sequences. Ribosomal RNAs have been used extensively for measuring evolutionary distances (11, 12) and these can be converted into phylogenetic trees by parsimony or distance matrix analyses. Because of their large size (relative to that of 5S and 5.8S rRNAs) and the existence of highly conserved and partially conserved sequence elements, the 16S-like or small-subunit rRNAs have been particularly useful for measuring both close and distant phylogenetic relationships (13,14). As part of a...

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mentioning

confidence: 99%

Phylogenetic relationships between chlorophytes, chrysophytes, and oomycetes.

Gunderson¹,

Elwood²,

Ingold³

et al. 1987

Proc. Natl. Acad. Sci. U.S.A.

352

129

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“…To confuse matters, in L. radicicola the occasional zoospore (perhaps those just released) has flagella attached about 1 pm from the apical end. Also, the zoospore of Olpidiopsis saprolegniae has been described as a secondary type because of body shape and the arrangement and presence of organelles (Bortnick et al 1985); however, flagella are subapically attached.…”

Section: Discussionmentioning

confidence: 99%

“…the zoospore of Lagenidium callinectes Couch is generally similar to zoospores of the Peronosporales (Bland and Amerson 1973;Gotelli 1974), although detailed studies of the flagellar apparatus are lacking. Studies of Blastulidium poedophthorum (Manier 1976), Haliphthoros milfordensis (Overton et al 1983), Lagenisma coscinodisci (Schnepf et al 1978), Olpidiopsis saprolegniae (Bortnick et al 1985), and Petersenia palmariae (Pueschel and van der Meer 1985) indicate that there is cytological variation among zoospores of the Lagenidiales. However, evidence is confused because these studies, with the exception of 0. saprolegniae (Bortnick et al 1985), do not report on details of the flagellar apparatus.…”

Section: Introductionmentioning

confidence: 98%

“…Studies of Blastulidium poedophthorum (Manier 1976), Haliphthoros milfordensis (Overton et al 1983), Lagenisma coscinodisci (Schnepf et al 1978), Olpidiopsis saprolegniae (Bortnick et al 1985), and Petersenia palmariae (Pueschel and van der Meer 1985) indicate that there is cytological variation among zoospores of the Lagenidiales. However, evidence is confused because these studies, with the exception of 0. saprolegniae (Bortnick et al 1985), do not report on details of the flagellar apparatus. Nonetheless, there is some indication, based both on this limited ultrastructural evidence as well as on morphological variation and habitat differences among taxa, that the Lagenidiales may be an artificial taxon for unrelated, funguslike heterokont organisms.…”

Section: Introductionmentioning

confidence: 98%

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Ultrastructure of the Lagena radicicola zoospore, including a comparison with the primary and secondary Saprolegnia zoospores

Barr¹,

Désaulniers²

1987

Can. J. Bot.

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BARR, D. J. S . , and DESAULNIERS, N. L. 1987. Ultrastructure of the Lugena radicicola zoospore, including a comparison with the primary and secondary Saprolegnia zoospores. Can. J . Bot. 65: 2161 -2176. The zoospore fine structure of Lugena radicicola Vanterpool & Ledingham is compared with the primary and secondary zoospores of Saprolegnia diclina Humphrey. The L. radicicola zoospore is broadly pyrifonn, it has two subapically attached flagella, a pyrifonn nucleus that has a fine fibrillar attachment to the posterior kinetosome, and a Golgi body next to the nucleus. There are various vesicles including dense body vesicles and several small expulsion vacuoles but there are no U-or K-bodies. It has a well-organized rootlet system comprising anterior and posterior doublet microtubules, a ribbed triplet that probably provides a cytoskeletal frame for the plasmalemma, and a multistranded, band-shaped rootlet of 4 to 10 microtubules. Cytoplasmic microtubules are very sparse. Interpretation of the rootlet systems was aided by computer graphics; 3-D images of the rootlet system were produced as stereo pairs on a Kontron image analyzer. Based on cell shape, position of the flagella, and angle of kinetosomes classification of the L. radicicola zoospore as either a primary or secondary type is imprecise; however, the various kinds of rootlets are similar to those found in the secondary zoospore of S. diclina but differ in structural detail and orientation. The transition zone in the flagellum of L. radicicola is simple and lacks the typical concertina body found in most oomycete flagella. The relationship of L. radicicola to the Oomycetes and various heterokont algal groups, based on comparative zoospore ultrastructure, is discussed. BARR, D. J. S., et DESAULNIERS, N. L. 1987. Ultrastructure of the Lugena radicicola zoospore, including a comparison with the primary and secondary Saprolegnia zoospores. Can. J . Bot. 65 : 2161 -2176. Les auteurs comparent les structures fines de la zoospore du Lugena radicicola Vanterpool & Ledingham avec les zoospores primaires et secondaires du Saprolegnia diclina Humphrey. La zoospore du L. radicicola est B peu prks pynfonne, posskde deux flagelles en position subapicale, un noyau pyrifonne muni d'un attachement fibrillaire fin au cinCtosome postCrieur, et un corps de Golgi voisin du noyau. On y retrouve diverses vCsicules incluant des vCsicules B corps dense, plusieurs petites vacuoles d'expulsion mais il n'y a pas de corps U ou K. I1 posskde un systkme radiculaire bien organis6 comprenant des doublets de microtubules antCrieur et postCrieur, un triplet cGtelC qui foumit probablement un cadre cytosquelettique B la plasmalemrne, et une radicule de 4 B 10 microtubules B plusieurs faisceaux en fonne de bande. Les microtubulescytoplasmiques sont t 2 s peu nombreux. Les auteurs ont tent6 dinterpkter le systkme radiculaire B l'aide de graphiques sur ordinateur; des images B trois dimensions du systkrme radiculaire ont Ct C produites en paires stCkoscopiques sur un analyseur d'image Kontron. S...

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“…, 1992Burr and Beakes 1994), regulated in part by selective encystment, germination and/or appressorium formation by zoospores (Sing andBartnicki-Garcia 1975, Kerwin et al 1992). There have been many investigations of oomycete zoospore ultrastructure (Beakes 1983, Powell et al 1985, Cho and Fuller 1989, Sadowski and Powell 1990, Randolph and Powell 1992, including examination of the roles of specific vesicle types and other organelles in the encystment process (Grove and Bracker 1978;Hardham 1985Hardham , 1986Gubler and Hardham 1988;Kelleher et al 1990). The bases of host specificity by these protists, however, are not known.…”

Section: Introductionmentioning

confidence: 98%

Regulation of attachment, germination, and appressorium formation by zoospores ofLagenidium giganteum and related oomycetes by chitin, chitosan, and catecholamines

et al. 1997

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Summary. Lagenidium giganteum (Oomycetes: Lagenidiales), a facultative parasite of mosquito larvae, infects the larval stage of most species of mosquitoes and a very limited number of alternate hosts. Host infection by this and other members of Oomycetes is initiated by motile, laterally biflagellate zoospores. Chemical bases for the various degrees of host specificity exhibited by these parasites is not known, but presumably involves receptors on the zoospore surface recognizing compounds either secreted by or on the surface of their hosts. Surface topography had no detectable effect on L. giganteum encystment or appressorium formation. Scanning electron microscopy documented the detachment of flagella during zoospore encystment. Bulbous knobs at the basal end of the detached flagellum were interpreted as encysting zoospores dropping the axoneme and/or the basal body and associated structures to which flagella are attached. Multiple signals appear to be involved in the initial steps ofL. giganteum host invasion. Zoospores of this parasite did not encyst on powdered preparations of chitin or chitosan (deacetylated chitin). Upon dissolution of chitosan in dilute acid followed by drying these solutions to form thin, transparent films, zoospores readily encysted. The degree of reacetylation of these films and the spacing of acetylated and deacetylated residues had no significant effect on zoospore encystment. Zoospores of a strain of Lagenidiurn myophilurn isolated from marine shrimp, that also infects mosquito larvae, encysted on chitosan films. No encystment of spores of the plant parasite Phytophthora capsici was observed on chitin or chitosan films. Simulation of cuticle sclerotization by incubating chitosan films with different catecholamines and tyrosinase significantly reduced zoospore encystment. Zoospores that encysted on chitosan films did not germinate in distilled water. Germination could be induced by adding microgram quantities of bovine serum albumin or proteins secreted by motile zoospores into the water, and to a lesser degree by some amino acids, but not by various cations. Zoospores encysted and germinated on the pupal stage of some mos-*Correspondence and reprints: Botany Department, Box 351330, University of Washington, Seattle, WA 98195, U.S.A. quito species. Appressoria were occasionally fort-ned, but most subsequently sent out another mycelial branch, apparently without attempting to pierce the pupal cuticle. Methylation of pupal exuviae with ethereal diazomethane or methanol/HC1 significantly increased zoospore encystment. Modification of chitin by catecholamines, lipids and protein on the epicuticular larval surface all affected host invasion.

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Microbody-like organelles as taxonomic markers among oomycetes

Cited by 34 publications

References 42 publications

Phylogenetic relationships between chlorophytes, chrysophytes, and oomycetes.

Phylogenetic relationships between chlorophytes, chrysophytes, and oomycetes.

Ultrastructure of the Lagena radicicola zoospore, including a comparison with the primary and secondary Saprolegnia zoospores

Regulation of attachment, germination, and appressorium formation by zoospores ofLagenidium giganteum and related oomycetes by chitin, chitosan, and catecholamines

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