The dinoflagellate Prorocentrum minimum (Pavillard) Schiller is known to be a major bloom‐causing microalga in the southern ocean of the Korean peninsula. The acclimation of this alga to darkness for 10 days was investigated by analyzing the content of various lipids, such as phospholipid (PL), galactolipid (GL), and triacylglyceride (TAG). Actively growing cultures of the alga under normal growth conditions (14:10 h LD [light:dark] cycle) were transferred to a growth chamber under conditions of no light and no carbon sources in the medium, and the culture was continued for another 10 days. The results showed that the content of TAG and GL decreased gradually during dark incubation, whereas the total PL content changed little; PC, PE, and PG decreased; and PS, PA, and PI increased. An increase in the activity of β‐oxidation and isocitrate lyase (ICL, a glyoxylate cycle enzyme) paralleled the decrease of TAG and GL. These observations strongly suggested that TAG and GL were utilized as alternative carbon sources by the cells under the prolonged dark cultivation. Light treatment of the cells cultivated in the dark for 10 days allowed them to attain the lipid composition that was observed in cells grown in light. These results strongly suggested that the cells maintained their metabolic integrity without unrecoverable cellular damages or cell death during 10 days of dark cultivation.
We have found nuclear, recessive mutants in Zea mays L where assembly of the major chlorophyll (a/b) light-harvesting complex (LHC) was not delayed relative to most other thylakoid protein complexes during thylakoid biogenesis. This contrasts with the normal development of maize chloroplasts (NR Baker, R Leech 1977 Plant Physiol 60: 640-644). All four mutants examined were allelic and virescent, and displayed visibly higher yields of leaf Chl fluorescence during greening. Fully greened mutants had normal leaf Chl fluorescence yield and normal levels of LHC, and grew to maturity under field conditions. Therefore, delayed LHC assembly is not an oblipte feature of thylakoid differentiation.Assigning the molecular basis for the mutation should provide information concerning reguation of LHC assembly. Several possibilities are discussed. The pleiotropic mutant phenotype is not attributable to defects in thylakoid glycerolipid synthesis. Thylakoids isolated from greening mutant leaf sections had elevated glycerolipid/Chl ratios. In addition, both the molar distribution and acyl composition of four major glycerolipids were normal for developing mutant thylakoids.Biogenesis ofphotosynthetic membranes in eucaryotes follows a programmed differentiation that allows efficient conversion of absorbed light to biochemical energy. The observed sequence is similar for differentiating thylakoids ofgreen algae (1) and higher plant etioplasts (2) and for thylakoids of developing protochloroplasts of several monocots including maize (4). PSI activity and PSI-dependent phosphorylation of ADP can be detected before PSII reaction center activity which, in turn, is followed by appearance of the water splitting activity. Insertion of the LHC2 into thylakoids lags behind the electron transport chain and may continue for some time after the redox carriers have achieved final activities (4, 16).
It is unknown at what level(s)
The most essential but missing components to understand and use toxic substances from marine microalgae are developing the fast, easy and economical determining technology for detecting it. In this paper we produced the antibodies against saxitoxin (STX). Mariculture keyhole limpet hemocyanin (mcKLH) and ovalbumin (OVA) were used as carrier proteins. mcKLH-STX conjugates were injected into the peritonial cavity of BALB/c mouse for immunization. After bleeding from mouse, anti-STX antiserum was isolated. Indirect enzyme-linked immunosorbent assays (ELISA) was performed to determine antiserum titer using the microtiter plate coated with free STX and OVA-STX. A goat anti-mouse IgG-phosphatase conjugate was used as secondary antibody to enable chromogenic reaction. Reactions of anti-STX antiserum were very specific on the OVA-STX and free STX. Sensitivity of anti-STX antiserum on STX was very high and STX detection limit was to be 64.9 ng/kg for indirect ELISA.
Oligo-alginate derivatives were extracted from brown algae and its antimicroalgal effects and reaction mechanism were investigated. Oligo-alginate derivatives were produced from sequential hydrolysis of high molecular weight alginate by treatment of 2 N HCl and 1% H2O2. Antimicroalgal activity of extracts was proportional to reaction time and activity was highest at 4 hrs. When oligo-alginate derivatives were treated to Akashiwo sanguinea and Cochlodinium polykrikoides, mobilities of cells were ceased. A. sanguinea cells were crushed and plasmolysis was induced in C. polykrikoides cells. To investigate the action mechanism of oligo-alginate derivatives, changes of intracellular (pHi) and extracellular pH (pHe) were determined in the microalgal cells exposed to 0.05% of oligo-alginate derivatives. pHi was decreased about 0.3 unit and pHe was increased about 0.9 unit. These results suggested that change of membrane potential by oligo-alginate derivatives could led to microalgal cell death.
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