HOOPS HJ, LONG JJ, HILE ES
FLAGELLAR
APPARATUS STRUCTURE IS SIMILAR BUT NOT IDENTICAL IN VOLVULINA-STEINII,
EUDORINA-ELEGANS, AND PLEODORINA-ILLINOISENSIS (CHLOROPHYTA) - IMPLICATIONS FOR
THE VOLVOCINE EVOLUTIONARY LINEAGE
J PHYCOL 30 (4): 679-689 AUG 1994
Abstract:
The colonial and multicellular members of the Volvocales can be arranged in
order of increasing size and complexity as the ''volvocine series.'' This
series is often assumed to reflect an evolutionary progression. The flagellar
apparatuses of previously examined algae are not consistent with a simple
lineage. The flagellar apparatuses of Astrephomene gubernaculifera Pocock, Gonium
pectorale Muller, Platydorina caudata Kofoid, Volvox rousseletii G. S. West,
and V. carteri f. weismannia (Powers) Iyengar differ from one another, and
there is no apparent progression in flagellar apparatus features from the
simple to complex colonial forms. We examined the flagellar apparatuses of
Volvulina steinii Playfair, Eudorina elegans Ehr., and Pleodorina illinoisensis
Kofoid and found then to be similar to one another. The basal bodies ave
connected by a distal fiber that is offset to the anti side of the cell. Two
microtubular rootlets originate on the inside of the basal bodies and extend
toward the syn side. The other two rootlets are oriented perpendicular to the
first two and are anti-parallel to each other. A coarsely striated component
underlies the four-membered rootlets and extends to the basal bodies. A
proximal fiber complex connects the two basal bodies. This complex consists of
a branched striated component on the cis side of each basal body. One part
extends toward the anti side of the cell, while the other extends into a
fibrous component that runs between basal bodies. An additional structure
extends in the anti direction from the trans side of each basal body. A fibrous
component extends past one basal body in all four species. This component goes
past the trans basal body in Volvulina steinii and the cis basal body in E.
elegans and P. illinoisensis. The flagellar apparatuses of these organisms are
similar to those of G. pectorale and Volvox carteri but different from the
other colonial volvocalean algae examined. The algae examined in this study
plus G. pectorale and V. carteri probably share a common evolutionary history
that postdates the transition from the unicellular to colonial habit. Such a
shared evolutionary history is a requirement of the volvocine hypothesis.
However, we have not observed progressive changes in the flagellar apparatus
correlated with increasing cell number, differentiation, and sexual specialization.
Thus, it is possible, but not certain, that G. pectorale, Volvulina steinii, E.
elegans, P. illinoisensis, and Volvox carteri may form part of a volvocine
lineage.
NOZAKI H, KUROIWA H, KUROIWA T
LIGHT AND
ELECTRON-MICROSCOPIC CHARACTERIZATION OF 2 TYPES OF PYRENOIDS IN GONIUM (GONIACEAE, CHLOROPHYTA)
J PHYCOL 30 (2): 279-290 APR 1994
Abstract:
The single, basal pyrenoids of Gonium quadratum Pringsheim ex Nozaki and
G. pectorale Muller (Goniaceae, Chlorophyta) differed in appearance when
vegetative colonies were cultured photoheterotrophically in medium containing
sodium acetate. Chloroplasts of G. quadratum had distinct pyrenoids when grown
in medium without major carbon compounds. However, the pyrenoids degenerated
and were markedly reduced in size when such cells were inoculated into a medium
containing 400 mg.L-1 of sodium acetate. No pyrenoids were visible under the
light microscope; however, with electron microscopy small pyrenoids and
electron-dense bodies were visible within the degenerating chloroplasts, which
had only single layers of thylakoid lamellae at the periphery. The chloroplasts
subsequently developed distinct pyrenoids and several layers of thylakoid
lamellae as the culture aged. In contrast, vegetative cells of G. pectorale
always showed distinct pyrenoids when cells were inoculated into medium
containing sodium acetate, sodium pyruvic acid, sodium lactate, and/or yeast
extract. Therefore, we propose two terms, ''unstable pyrenoids'' and ''stable
pyrenoids, '' for pyrenoids of G. quadratum and G. pectorale, respectively.
Chloroplasts of the colonial green flagellates should thus be examined under
various culture conditions in order to determine whether their pyrenoids are
unstable or stable when pyrenoids are used as taxonomic indicators. Immunogold
electron microscopy showed that the ratios of gold particle density of
ribulose-1,5-biphosphate carboxylase/oxygenase (RuBisCO) between pyrenoid
matrix and chloroplast stroma in G. quadratum grown in medium with or without
sodium acetate were lower than those of G. pectorale. Heavy labeling by
anti-RuBisCO was observed in both the electron-dense bodies and pyrenoid matrix
of G. quadratum. This is the first electron microscopic demonstration of
degeneration and development of both pyrenoids and thylakoid lamallae in the
chloroplast as a function of culture condition in green algae.
NOZAKI H, ITOH M
PHYLOGENETIC-RELATIONSHIPS
WITHIN THE COLONIAL VOLVOCALES (CHLOROPHYTA) INFERRED FROM CLADISTIC-ANALYSIS
BASED ON MORPHOLOGICAL DATA
J PHYCOL 30 (2): 353-365 APR 1994
Abstract:
A cladistic analysis was used to deduce the phylogenetic relationships within
the colonial Volvocales. Forty-one pairs of characters related to gross
morphology and ultrastructure of vegetative colonies as well as asexual and
sexual reproduction were analyzed based on parsimony, using the PAUP 3.0
computer program, for 25 species belonging to nine volvocacean and goniacean
genera of the colonial Volvocales. Chlamydomonas reinhardtii Dangeard was the
outgroup. The strict consensus tree indicated the presence of two monophyletic
groups, one composed of all the volvocacean species analyzed in this study and
the other containing the goniacean species except for the four-celled species Gonium
sociale (Dujardin) Warming. In addition, these two groups constitute a large
monophyletic group, to which G. sociale is a sister group. A new combination
Tetrabaena socialis (Dujardin) Nozaki et Itoh and a new family Tetrabaenaceae
Nozaki et Itoh are thus proposed for G. sociale. In addition, the analysis
suggests that the volvocacean genera Eudorina and Pleodorina are paraphyletic
groups, respectively, and that the monotypic genus Yamagishiella has no
autapomorphic characters and represents primitive features of the anisogamous
and oogamous genera of the Volvocaceae. Phylogenetic relationships within the
Volvocaceae and the Goniaceae, as well as the various modes of sexual
reproduction exhibited by these organisms, are discussed on the basis of the
analysis.
COLEMAN AW, SUAREZ A, GOFF LJ
MOLECULAR
DELINEATION OF SPECIES AND SYNGENS IN VOLVOCACEAN GREEN-ALGAE (CHLOROPHYTA)
J PHYCOL 30 (1): 80-90 FEB 1994
Abstract:
Two species of the colonial flagellate family Volvocaceae are worldwide in
distribution yet exhibit contrasting species structure. Geographically
disparate isolates of Gonium pectorale Mueller can interbreed while
isolates of Pandorina morum Bory behave quite differently, More than 20
sexually isolated subpopulations occur within this species; these have been
termed ''syngens'' (sensu Sonneborn). Because prezygotic barriers to mating
cause intersyngen pairings to fail, breeding analyses cannot be used to estimate
genetic relatedness among the syngens of P. morum. DNA comparisons provide an
alternative method of assessing genetic relatedness. We compared the nucleotide
sequence of the internal transcribed spacer (ITS) region of the nuclear
ribosomal repeat among clones of P. morum and of G. pectorale. Members of
syngens of P. morum with distribution restricted to one small geographical area
show great similarity. Likewise, members of any syngen of worldwide
distribution show near uniformity, even those from different continents.
However, the ITS sequence of each syngen differs from that of other syngens. In
contrast, G. pectorale, which has an ITS region that is remarkably uniform
throughout the world, appears to consist of a single syngen within