Structure and significance of cruciate flagellar root systems in green algae: Female gametes ofBryopsis lyngbyei (Bryopsidales)

Melkonian, Michael

doi:10.1007/bf02074128

Cited by 28 publications

(30 citation statements)

References 22 publications

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“…Par ailleurs, selon Melkonian (1981), les gamè-tes femelles de Bryopsis lyngbyei ne comportent pas de structure d'accouplement. Il apparaît donc qu'il existe des zones différenciées du plasmalemme qui sont variables dans leur localisation, leur structure et leur rôle.…”

Section: Lettres Bot Aniql'esunclassified

Aspects ultrastructuraux de la fécondation chez l'Acrosiphonia spinescens(Kütz.) Kjellm. (Acrosiphoniales, Chlorophyta)

Jónsson¹,

Chesnoy

1984

Bulletin de la Société Botanique de France. Lettres Botaniques

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Résumé.-Des planozygotes négativement phototactiques de l'Acrosiphonia spinescens, espèce monoïque, ont été fixés quelques minute~; après la libération des gamètes. Ils portent chacun quatre flagellei égaux, acronématés, rabattus en arrière et insérés dans une papille apicale. La fusion gamétique est latérale. Les sectiom; de la papille montrent quatre corpuscules basaux, de structure classique, à arrangement groüièrement cruciforme. Deux corpuscules basaux appartenant chacun à un gamète de sexe opposé sont pre11que en contact par leurs extrémités proximales, tandis que les deux autres sont rejetés latéralement en formant des angleii inégaux. Cette disposition suggère un mouvement de rotation et de glisiiement des corpuscules basaux au cours de la fécondation. Deux racines flagellaires superficielles sont associées à chacun des corpuscules basaux, l'une avec 2 microtubules, l'autre avec 3. Les deux types de racines sont réunis dans le plan de fusion des gamètes, dans la région apicale. Dans le plan opposé, les deux racines sont toujours séparéei. Ues microtubules cytosquelettiques sont également préients. Il n'a pas été observé de rhizoplastes ni de structures striées aSiociées aux microtubules racinaires. Microtubules racinaires et corpu$cules basaux jouent probablement un rôle morphogénétique lor~; du positionnement des gamètes. On note, de plus, un ligament strié connectant les deux corpuscules basaux d'un même gamète, l'exiitence de capsules terminales, d'une masse amorphe en forme de crochet, sous la région proximale des corpuscules basaux.Le planozygote réunit dans un cytoplasme chargé en ribosomes, deux noyaux, une grande mitochondrie riche en zor· ~s à ADN, remontant à proximité de l'appareil flagellaire, deii gouttelettes lipidiques, dei vésiculeii g.,lgiennes et des vacuoleii. Les deux chloroplastes comportent chacun un pyrénoïde et un stigma bJ~trate. Le plasmalemme, dépourvu d'écailles, est recouvert de granules osmiophiles qui ne se trouvent pas chez les gamètes non libérés. Summar) .-i\egativelely phototactic planozygotes of the bisexual alga Acrosiphonia spinescens were fixee! a few minutes after gamete release. They bear four blackwards directed isokont flagella with conspicuoUii acronema. Flagellar insertion is apical. Gametic fusion iii lateral. Sections through the apical papilla iihow four roughly cruciately arranged basal bodies. Two basal bodieii, each from opposite mating type, are almost in contact by their proximal ends, whereas two others are considerably diiiplaced. This configuration suggests a rotation and sliding movements of basal bodies ,during fertilization. Two flagellar rooùetli are linked to each basal body, one containing 2 microtubules, the other 3. The two sets of rootlets are associated in the plane of fusion, at !east distally. ln the oppoiiÏte plane, microtubular rootlets are alwayli separated. Cytoskeletal microtubules occur. Neither rhizoplasts or microtubular associated striated structures were observed. Microtuhular root-(*)Manuscrit reçu le 5 juin 1984 ; accepté le ...

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Section: Lettres Bot Aniql'esunclassified

Aspects ultrastructuraux de la fécondation chez l'Acrosiphonia spinescens(Kütz.) Kjellm. (Acrosiphoniales, Chlorophyta)

Jónsson¹,

Chesnoy

1984

Bulletin de la Société Botanique de France. Lettres Botaniques

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“…2 flagella in the numbering convention of Moestrup and Hori (1989). This numbering of flagella is based on the eyespot position, which is probably consistent in advanced chlorophytes (Melkonian and Robenek 1984, Holmes and Dutcher 1989, Melkonian 1989, Kreimer 2001). However, this numbering system is inapplicable to the male gametes because they have no eyespot.…”

Section: Resultsmentioning

confidence: 52%

“…This streak may correspond to the 2s root because the gamete of Caulerpa has four cruciately arranged microtubular root system. In addition, its eyespot is associated with the 2s and 2d root (Hori 1981), which extends down to the cell posterior from the basal body and is located directly beneath the cell membrane, as in other siphonous green algae (Melkonian andRobenek 1984, Kreimer 2001). Therefore, the left and right flagella in Fig.…”

Section: Resultsmentioning

confidence: 99%

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Behavior of Flagella and Eyespot during Fertilization of Anisogametes in Caulerpa racemosa (Forsskal) J. Agardh var. laetevirens (Montagne) (Ulvophyceae, Chlorophyta) Revealed by Field Emission Scanning Electron Microscopy

Miyamura

2005

CYTOLOGIA

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SummaryRespective fates of male and female flagella and the eyespot during fertilization of ulvophycean alga Caulerpa racemosa (Forsskål) J. Agardh var. laetevirens (Montagne) were studied using field emission scanning electron microscopy (FE-SEM). FE-SEM allowed visualization of the eyespot of the biflagellate gamete. The female gamete has one eyespot on a posterior position of the cell body; the male gamete does not. The female gamete eyespot was oriented to the direction of the plane of the flagellar beat. The female gamete is larger than the male one and has the only eyespot. For those reasons, the author followed the fate of the flagella and eyespot during fertilization. When both gametes were mixed, the initial cytoplasmic contact and cell fusion between them usually took place at the anterior end slightly below the flagellar base. In most mating pairs, the female gamete fuses at the left side of the eyespot and male gamete at a cell surface that is perpendicular to the plane of the flagellar beat. As fusion proceeds, the gamete pair is transformed into a quadriflagellate planozygote in which two flagella each from the male and female gametes point in nearly the same direction. In particular, the no. 2 flagellum of the female gamete and one male flagellum were directed to the eyespot. These observations indicated that cell fusion at the particular area of the gamete is important for proper arrangement of the flagella and eyespot in the planozygote.

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“…(a Based on Ettl, 1976;b on Ringo, 1967b on Ringo, ) et al, 1980Hoffmann, 1984;Melkonian, 1977Melkonian, , 1978Melkonian, , 1983Moestrup, 1978Moestrup, , 1982. Bakker & Lokhorst, 1985;Floyd et al, 1985;Gori, 1979;Hirayama & Hori, 1984;Hoops et al, 1982;Hold, 1977;Hori & Kobara, 1982;J6nsson & Chesnoy, 1984;Lokhorst, 1984;Melkonian, 1979Melkonian, , 1980Melkonian, , 1981bMiyaji & Hori, 1984;O'Kelly et al, 1984;Roberts et al, 1980Roberts et al, , 1981Sluiman, 1985b;Sluiman et al, 1980bSluiman et al, , 1982Stuessy et al, 1983). This flagellate cell type is characteristic of the class Ulvophyceae.…”

Section: Architecture Of the Flageflate Cellmentioning

confidence: 97%

The emergence of a new chlorophytan system, and Dr. Kornmann's contribution thereto

Hoek

Stam

Olsen

1988

Helgolander Meeresunters

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In traditional chlorophytan systems the organizational level was the primary character for the distinction of main groups (classes and orders). For instance, in Fott (1971), the flagellate level corresponds with the Volvocales, the coccoid level with the Chlorococcales, the filamentous level with the Ulotrichales, the siphonocladous level with the Siphonocladales, and the siphonous level with the Bryopsidales. The new system presented here is an elaboration and emendation of recently proposed taxonomies and their underlying phylogenetic hypotheses, and it is mainly based on ultrastructural features which have become available over the last 15 years. The following criteria are used for the distinction of classes and orders: (1) architecture of the flagellate cell (flagellate cells are considered as the depositories of primitive characters); (2) type of mitosis-cytokinesis; (3) place of meiosis in the life history and, consequently, the sexual hfe history type; (4) organizational level and thallus architecture; (5) habitat type (marine versus feshwater and terrestrial); (6) chloroplast type.

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Structure and significance of cruciate flagellar root systems in green algae: Female gametes ofBryopsis lyngbyei (Bryopsidales)

Cited by 28 publications

References 22 publications

Aspects ultrastructuraux de la fécondation chez l'Acrosiphonia spinescens(Kütz.) Kjellm. (Acrosiphoniales, Chlorophyta)

Aspects ultrastructuraux de la fécondation chez l'Acrosiphonia spinescens(Kütz.) Kjellm. (Acrosiphoniales, Chlorophyta)

Behavior of Flagella and Eyespot during Fertilization of Anisogametes in Caulerpa racemosa (Forsskal) J. Agardh var. laetevirens (Montagne) (Ulvophyceae, Chlorophyta) Revealed by Field Emission Scanning Electron Microscopy

The emergence of a new chlorophytan system, and Dr. Kornmann's contribution thereto

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