Schagerl M, Angeler DG
The
distribution of the xanthophyll loroxanthin
and its systematic significance in the colonial Volvocales
(Chlorophyta)
PHYCOLOGIA 37 (2): 79-83 MAR 1998
Abstract:
The distribution of the xanthophyll loroxanthin [(3R,3'R,6'R)-
beta,epsilon-carotene-3,19,3'-triol] within colonial volvocalean
families was analyzed by reversed-phase high pressure Liquid chromatography (rP-HPLC). The results demonstrate that loroxanthin
is a physiological marker delineating the families Tetrabaenaceae
Nozaki et Itoh and Goniaceae (Pascher) Pascher. Thus loroxanthin may be
considered to be of systematic significance within the Volvocales,
and its use as a marker supports recent ideas on phylogenetic
relationships. Within the Volvocaceae Ehrenberg, its infraspecific disjunct
distribution indicates that it is not useful systematically in this family and
that it varies even within a morphologically defined species. The pattern of loroxanthin distribution was compared with molecular data
and traditional characters.
Nozaki H, Ohta N, Yamada T, et al.
Characterization
of rbcL group IA introns
from two colonial volvocalean species (Chlorophyceae)
PLANT MOL BIOL 37 (1): 77-85 MAY 1998
Abstract:
Group I introns were reported for the first time in
the large subunit of Rubisco (rbcL)
genes, using two colonial green algae, Pleodorina
californica and Gonium multicoccum
(Volvocales). The rbcL gene
of P. californica contained an intron
(PlC intron) of 1320 bp harboring an open reading frame (ORF). The G. multicoccum rbcL gene had two
ORF-lacking introns of 549 (GM1 intron)
and 295 (GM2 intron) base pairs. Based on the
conserved nucleotide sequences of the secondary structure, the PlC and GM1 introns were assigned
to group IA2 whereas the GM2 intron belonged to group
IA1. Southern hybridization analyses of nuclear and chloroplast DNAs indicated that such intron-containing
rbcL genes are located in the chloroplast genome.
Sequencing RNAs from the two algae revealed that
these introns are spliced out during mRNA maturation.
In addition, the PlC and GM1 introns
were inserted in the same position of the rbcL exons, and phylogenetic analysis
of group IA introns indicated a close phylogenetic relationship between the PlC
and GM1 introns within the lineage of bacteriophage group IA2 introns.
However, P. californica and G. multicoccum
occupy distinct clades in the phylogenetic
trees of the colonial Volvocales, and the majority of
other colonial volvocalean species do not have such introns in the rbcL genes.
Therefore, these introns might have been recently
inserted in the rbcL genes independently by
horizontal transmission by viruses or bacteriophage.