Biology Reference
In-Depth Information
product in members of most orders of red seaweeds is clearly the heteroside
floridoside (
-
D
-galactopyranosyl-(1-2)-glycerol), while most members of the
Ceramiales (Florideophyceae) generally synthesize and accumulate instead of
floridoside,
a
the chemically related digeneaside (
a
-
D
-mannopyranosyl-(1-2)-
glycerate) (Kremer
1978
).
Already Lindberg (
1955
) provided evidence that, in addition to floridoside,
members of the Bangiales (Bangiophyceae) contain an isomeric form of
floridoside, isofloridoside (
-
D
-galactopyranosyl-(1-1)-glycerol). Wickberg (
1958
)
later reported isofloridoside in
Porphyra umbilicalis
as a uniform mixture of
D
- and
L
-forms. More recently, the chemical structures and configurations of all three
heterosides from
Porphyra perforata
were investigated, and the occurrence of
floridoside along with both
D
- and
L
-isofloridoside was verified (Meng et al.
1987
), while the strong involvement of all these compounds in the process of
osmotic acclimation was experimentally proven in
P. columbina
(Karsten et al.
1993a
). More interesting is the observation of different heteroside patterns in
Porphyra
species from different biogeographic regions in Europe, Africa, North
America, Asia, and Australia (Karsten
1999
). The composition of the three
compounds varied among the species studied. In
P. columbina
from Australia,
L
-isofloridoside was always quantitatively dominant, while floridoside was the
major component in
P. dioica
from the North Sea.
D
-Isofloridoside was usually
present in small concentrations, except in
P. perforata
from the Pacific coast of
the USA where it occurred in equal concentrations along with floridoside and
L
-isofloridoside (Karsten
1999
). These results point to species-specific different
enzymatic activities of the underlying anabolic pathways, which are, however, not
completely understood.
The consistent presence of digeneaside together with a new compound was
noted in some members of the genus
Hypoglossum
(Delesseriaceae, Ceramiales),
and a chemical survey in members of this taxon resulted in the identification of
digalactosylglycerol
a
!
6)-ß-
D
-
galactopyranoside), which was strongly involved in osmotic acclimation (Karsten
et al.
2005
). Surprisingly, digalactosylglycerol has never been reported for any
other seaweed species before, even though it most probably represents the main
photosynthetic product in
Hypoglossum barbatum
and
H. heterocystideum
(Karsten
et al.
2005
).
The disaccharide trehalose was detected in several members of the Ceramiales.
While some taxa of this order such as
Aglaothamnion
spp. exhibited only trehalose,
others such as
Delesseria sanguinea
showed trehalose together with digeneaside.
Although more recent data indicate that only a few Ceramialean taxa are capable of
synthesizing trehalose (Karsten et al.
2007
), the summarized results in the review of
Craigie (
1974
) point to other Florideophycean species also forming this disaccha-
ride. Therefore, this compound may be more widely distributed among the
Rhodophyta than currently thought.
Most interesting is the fact that in some Ceramiales such as in the mangrove-
associated genera
Bostrychia
and
Caloglossa
as well as in some early diverging red
algal lineages the polyols mannitol, sorbitol, and dulcitol can be found (Karsten and
(2,3-dihydroxypropyl
(
a
-
D
-galactopyranosyl)-(1
