ISSN 1021-4437, Russian Journal of Plant Physiology, 2007, Vol. 54, No. 2, pp. 171–183. © Pleiades Publishing, Ltd., 2007.
Published in Russian in Fiziologiya Rastenii, 2007, Vol. 54, No. 2, pp. 195–208.
The term “host factor” (HF) was ﬁrst used to
describe the property of
tissue homogenates to elicit the selec-
tive release of newly ﬁxed carbon by freshly-isolated
symbiotic dinoﬂagellates in vitro . There is now a
substantial body of literature describing host factor and
its properties in a diversity of anthozoan symbioses [2–6].
Many of HF properties vary depending on the host,
including the host chemical nature [5–10], the stability of
HF activity to heat [1–3, 5, 9–11], the HF impact on car-
bon ﬁxation [2, 3, 5, 7, 9, 12, 13], and its effect on cul-
tured and nonsymbiotic dinoﬂagellates [6, 8].
Although the behavior of the crude cnidarian’s host
factor (CHF) is highly variable, two consistent proper-
ties are well established: (1) the release of carbon by
dinoﬂagellates incubated in CHF is always signiﬁ-
cantly higher than by those incubated in seawater alone,
and (2) carbon is selectively released by the dinoﬂagel-
lates to the incubation medium primarily as glycerol,
with smaller amounts of glucose, organic acids, amino
acids, and lipids [1–3, 5, 7, 9, 11].
The way in which CHFs favor the selective release
of carbon from isolated dinoﬂagellates remains unclear,
although two mechanisms have been suggested. HFs
Effects of Free Amino Acids on the Photosynthetic Carbon
Metabolism of Symbiotic Dinoflagellates
K. Y. Biel
a, d, e
, R. D. Gates
, and L. Muscatine
Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow oblast, 142290 Russia
Department of Organismic Biology, Ecology and Evolution, University of California, Los Angeles, CA 90095, USA
Soda Canyon Wine Laboratory, Napa Valley, CA 94558, USA
Biosphere Systems International, 12138 N. Sterling Avenue, Tucson, Az 85755, USA;
fax: 1 (520) 908-0819; e-mail: firstname.lastname@example.org
Centro de Investigación en Alimentación y Desarrollo, Hermosillo, 83000 Sonora, México
Received December 1, 2004
—Synthetic host factor (SHF) was used in parallel with crude cnidarian’s host factor (CHF) to inves-
tigate their effects on both photosynthetic carbon metabolism and the ﬁrst step of lipid synthesis in the symbi-
of the sea anemone
Several species have been
studied, namely, sea anemone
, reef coral
, and green alga
Both short-term and long-term experiments with radioactive carbon have shown a higher rate of the
C photoaccumulation with host factor(s) than of dinoﬂagellates located in artiﬁcial sea water (ASW)
alone. In dinoﬂagellates incubated with both ASW and CHF,
C-labeled glycerol was detectable after 15 s of
alga illumination. In dinoﬂagellates isolated from
and incubated in CHF and SHF and in
dinoﬂagellates isolated from
and incubated in CHF, a higher percentage of
C was found in the
glycerol as compared to the ASW trial. At the same time, in ASW trial the radioactive label was primarily
located in ethanol-soluble lipid fraction. Similar results were observed when dinoﬂagellates isolated from
were incubated with aspartate or glutamate. But there was no effect with taurine, serine, valine,
glycine, or lysine.
, incubated in salt-free CHF, partitioned a greater percent of
C into the glycerol
and less into the ethanol-soluble lipids as compared to the corresponding control incubations. The amount of
C in neutral and polar lipids was identical in that in
dinoflagellates incubated in ASW or CHF.
The arrays of neutral
C-lipids produced under both ASW alone and ASW with CHF conditions, and over time
were not signiﬁcantly distinguishable. Host factors appeared to provide an optimum environment to sustain
maximum metabolic efﬁciency. A biochemical model, based on the quantitative and qualitative assessment of
carbon pathways in dinoﬂagellates incubated both in host factor and sea water alone, is presented.
Key words: Symbiodium purchrorum - Aiptasia pulchella - Pocillophora damicornis - Chlamydomonas rein-
hardii - cnidarians - host factor - symbiosis - photosynthesis - respiration
: ASW—Tropic Marin
artiﬁcial sea water; CHF—
crude cnidarian’s host factor; DHOAP—dihydroxyacetone phos-
phate; DNPH—2, 4-dinitrophenylhydrazine; FAA—free amino
acids; Fum—fumarate; Gly-3-P—glycerol-3-phosphate; HF—host
factor; HSM—high salt minimal medium; OAA—oxaloacetic
acid; 3-PGA—3-phosphoglyceric acid; PEP—phosphoenolpyru-
vate; SHF—synthetic host factor; SP—sugar phosphates; TAP—
Tris–acetate-phosphate buffer, Tau—taurine, Suc—succinate.
The text was submitted by the authors in English.