2005
Yoshida H, Yokomori T,
Suyama A. A simple classification of the volvocine algae by formal languages.
BULLETIN OF MATHEMATICAL BIOLOGY 67 (6): 1339-1354 NOV 2005
Abstract: There are several explanations of why certain primitive
multicellular organisms aggregate in particular forms and why their constituent
cells cooperate with one another to a particular degree. Utilizing the
framework of formal language theory, we have derived one possible simple
classification of the volvocine algae-one of the primitive multicells-for some
forms of aggregation and some degrees of cooperation among cells. The volvocine
algae range from the unicellular Chlamydonionas to the multicellular Volvox
globator, which has thousands of cells. The classification we use in this paper
is based on the complexity of Parikh sets of families on Chomsky hierarchy in
formal language theory. We show that an alga with almost no space closed to the
environment, e.g., Gonium pectorale, can be characterized by PsFIN, one with a
closed space and no cooperation, e.g., Eudorina elegans, by PsCF, and one with
a closed space and cooperation, e.g., Volvox globator, by Ps lambda SC. This
classification should provide new insights into the necessity for specific
forms and degrees of cooperation in the volvocine algae. (c)
2005 Society for Mathematical Biology.
Cheng Q, Pappas V, Hallmann A, et al. Hsp70A
and GlsA interact as partner chaperones to regulate asymmetric division in Volvox.
DEVELOPMENTAL BIOLOGY 286 (2): 537-548
Abstract: GlsA, a J-protein chaperone, is required for the
asymmetric divisions that set aside germ and somatic cell precursors during
embryogenesis in Volox carteri, and previous evidence indicated that this
function requires an intact Hsp70-binding site. To determine if Hsp70A, the
only known cytoplasmic Hsp70 in V. carteri, is the chaperone partner of GlsA,
we investigated the localization of the two proteins during critical stages of
embryogenesis and tested their capacity to interact. We found that a
substantial fraction of Hsp70A co-localizes with GlsA, both in interphase and
mitotic blastomeres. In addition, Hsp70A coimmunoprecipitated with GlsA, and
co-expression of GlsA and Hsp70A variants partially rescued the Gls phenotype
of a glsA mutant, whereas neither variant by itself rescued the mutant
phenotype. Immunofluorescence analysis demonstrated that GlsA is about equally
abundant in all blastomeres at all cleavage stages examined but that Hsp70A is
more abundant in anterior (asymmetrically dividing) blastomeres than in
posterior (symmetrically dividing) blastomeres during the period of asymmetric
division. We conclude that Hsp70A and GlsA function as chaperone partners that
regulate asymmetric division and that the relative abundance of Hsp70A in
asymmetrically dividing embryos may determine which blastomeres divide
asymmetrically and which do not.
Aono N, Inoue T, Shiraishi H. Genes
specifically expressed in sexually differentiated female spheroids of Volvox
carteri.
JOURNAL OF BIOCHEMISTRY 138 (4): 375-382 OCT 2005
Abstract: Volvox carteri is a multicellular green
alga with only two cell types, somatic cells and reproductive cells.
Phylogenetic analysis suggests that this organism has evolved from a
Chlamydomonas-like unicellular ancestor along with multicellularity, cellular
differentiation, and a change in the mode of sexual reproduction from isogamy
to oogamy. To examine the mechanism of sexual differentiation and the evolution
of oogamy, we isolated 6 different cDNA sequences specifically expressed in
sexually differentiated female spheroids. The genes for the cDNAs were
designated SEF1 to SEF6. The time course of accumulation of each mRNA was shown
to be distinct. The expression of some of these genes was not significantly
affected when the sexual inducer was removed after the induction of sexual
development. Sequence analysis indicates that SEF5 and SEF6 encode
pherophorin-related proteins. Of these, SEF5 has the unique structural feature
of a polyproline stretch in the C-terminal domain in addition to the one found
in the central region.
Wadhwa V, Kumar S, Rai S, et al. A 'pseudo
outbreak' of the contamination of blood cultures with Volvox globator.
ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 99 (7): 719-720 OCT 2005