经济海藻红毛菜原位光合作用日变化

利用光合气体交换和叶绿素a荧光技术测定了原位沉水和干出条件下红毛菜光合作用的日变化,结果显示与沉水藻体相比,中午干出藻体光合速率、光系统II最大光化学效率(Fv/Fm)、实际光化学效率(ΦPSⅡ)、光化学淬灭系数(qP),光响应曲线初始斜率(ɑETR)和相对电子传递速率(rETR)值下降更明显。干出藻体重新入水后,其叶绿素a荧光参数在两个小时内可以完全恢复到沉水藻体的水平。红毛菜叶绿素a、类胡萝卜素、藻红蛋白的含量在一天中并没有出现明显变化。以上结果表明红毛菜日生长在中午要经历光抑制过程,干出状态下光抑制更严重;干出和沉水藻体光合速率都可以在傍晚得以恢复;红毛菜光系统II反应中心可以通过增加热耗散和降低光合电子传递速率等策略来应对光抑制。     

Stable chloroplast transformation of the unicellular red alga Porphyridium species

Red algae are extremely attractive for biotechnology because they synthesize accessory photosynthetic pigments (phycobilins and carotenoids), unsaturated fatty acids, and unique cell wall sulfated polysaccharides. We report a high-efficiency chloroplast transformation system for the unicellular red microalga Porphyridium sp. This is the first genetic transformation system for Rhodophytes and is based on use of a mutant form of the gene encoding acetohydroxyacid synthase [AHAS(W492S)] as a dominant selectable marker. AHAS is the target enzyme of the herbicide sulfometuron methyl, which effectively inhibits growth of bacteria, fungi, plants, and algae. Biolistic transformation of synchronized Porphyridium sp. cells with the mutant AHAS(W492S) gene that confers herbicide resistance gave a high frequency of sulfomethuron methyl-resistant colonies. The mutant AHAS gene integrated into the chloroplast genome by homologous recombination. This system paves the way for expression of foreign genes in red algae and has important biotechnological implications.     

Stabilization and modulation of the phycobilisome by calcium in the calciphilic freshwater red alga Bangia atropurpurea

The bangiophycean filamentous red alga Bangia atropurpurea is distributed in freshwater habitats such as littoral and splash zones of lakes or rapid currents distant from the sea. In these habitats, the distribution and growth of this alga appear to be related to hard water rich in calcium ions. To characterize the eco-physiological properties of this calciphilic red alga, we examined the effects of long-term and short-term Ca(2+) depletion on photosynthetic growth of the thallus and on the phycobilisome. Long-term culture experiments suggested that higher Ca(2+) concentrations (>50mgL(-1)) were required to sustain thallus growth and pigmentation of cells. In short-term Ca(2+)-depletion treatments, fluorescence derived from phycoerythrin (PE) fluctuated, although the absorption spectra of the thalli did not change. After 30 min of Ca(2+) depletion, the fluorescence lifetime of PE became markedly longer, indicating that the energy transfer from PE to phycocyanin (PC) was suppressed. The fluorescence lifetime of PE returned to its original value within a short time after 4h of Ca(2+) depletion, however, energy transfer from PE to PC was still suppressed. This suggested that the excitation energy absorbed by PE was quenched during prolonged Ca(2+) depletion. The efficient energy transfer from PC and allophycocyanin were unchanged during these treatments.     

The chloroplast genome of a chlorophylla+c-containing alga,Odontella sinensis

The chloroplast genome of a marine centric diatom,Odontella sinensis, was cloned and sequenced. The circular genome is 119,704 bp in length (AC=Z67753;). It contains an inverted repeat sequence of 7,725 bp separating two single-copy regions of 38,908 and 65,346 bp, respectively, and 174 genes and open reading frames, of which nine are duplicated within the inverted repeat segments.     

Dynamic changes of protoplasmic volume and of fine structure during osmotic adaptation in the intertidal red alga Porphyra umbilicalis

Abstract Cells of Porphyra umbilicalis show a biphasic osmotic regulatory response. After transfer from 1 × into 3.5 × artificial seawater medium (osmotic upshock) the protoplasts shrink rapidly, then recover their original size within 3 h and continue to increase over the next 14 d. After retransfer from 3.5 × into 1 × medium (osmotic downshock) the protoplasts swell immediately and then adjust to the normal size in 1 x medium. Parallel to the shrinkage of the protoplasts after osmotic upshocks the plasmalemma at first gets a wavy surface which becomes smooth again during the following adaptation process. Immediately after osmotic upshock the vacuolar volume increases and it decreases drastically after osmotic downshock. After osmotic upshocks only small vacuoles are present at first. In adapted plants, however, the vacuolar system is mainly composed of large vacuoles. The volume of the protoplasm without the vacuoles is regulated osmotically. Parallel to the increase in the vacuolar volume after osmotic upshocks there is an increase in the number of intramembraneous particles on the PF-face of the tonoplast. This high value is reduced rapidly to the original number after osmotic downshock. The findings are discussed in relation to the function of the vacuoles as compartments of inorganic ion accumulation during osmotic adaptation.     

The fine structure of gas-vacuoles released from cells of the blue-green alga Anabaena flos-aquae

Summary Cells of the blue-green alga Anabaena flos-aquae were ruptured and the gas-cylinders, which comprise the gas-vacuoles, were released. The gas-cylinders released retained their same shape and structure: 70 m or more wide, 0.2–0.9 long, with conical ends. Staining with phosphotungstic acid showed the membrane to be made up of particles arranged in rows, about 5 m apart, running round the cylinder at right angles to the long axis. Some of the cylinders became flattened during the preparation. Rounding-off of the gas-cylinders on isolation, described by others, was not encountered. However, some of the isolated gas-cylinders were considerably wider than 70 m and it is possible that they tend to shorten and widen on isolation from the cell.     

Phototropism in a red alga, Griffithsia pacifica

In the red alga, Griffithsia pacifica, shoot portions of a plantare positively phototropic and rhizoids are negatively phototropic.We have studied the phototropic response of rhizoids which elongateby tip growth. For 45 min after the beginning of unilateralillumination a rhizoid grows straight, then phototropic curvaturebegins and continues rapidly until the rhizoid is growing awayfrom the light. Curvature is 70–80% complete after 3 hr.If the unilateral stimulus is given for a short time (15 min),curvature again begins at 45 min. However, within an additional30–45 min the rhizoid stops growing away from the lightand wanders back towards its original direction of growth. Phototropismis elicited by light of wavelengths from 350 nm to 500 nm; inlight of wavelengths above 550 nm, little, if any, responseoccurs. ¹Present address: Division of Natural Sciences, University ofCalifornia, Santa Cruz, California 95064, U.S.A. (Received December 10, 1976; )     

Observations on the fine structure of Chlamydobotrys stellata,with particular reference to its unusual chloroplast structure

Summary Eight species of Olpidium are reported from freshwater algae and from soils in Iceland. Similarities between Olpidium endogenum and O. entophytum are discussed. On the basis of the specimens at hand and the substrates in which they occur, O. zygnemicola and O. spirogyrae are reduced to synonymy with O. entophytum and O. endogenum respectively. Olpidioid fungi in Oedogonium and sterilized pine pollen are tentatively assigned to the doubtfully distinct species O. saccatum and O. utriculiforme. Olpidium pendulum, O. luxurians, and O. longicollum occur in pine pollen bait in gross water cultures of soil. These three species are only doubtfully distinct entities. Olpidium rhizophlyctidis is reported for the first time from Iceland.     

Characterization, cloning, and evolutionary history of the chloroplast and cytosolic class I aldolases of the red alga Galdieria sulphuraria

Two fructose-1,6-bisphosphate aldolases from the acido- and thermophilic red alga Galdieria sulphuraria were purified to apparent homogeneity and N-terminally microsequenced. Both aldolases had similar biochemical properties such as Km (FBP) (5.6-5.8 microM) and molecular masses of the native enzymes (165kDa) as determined by size exclusion chromatography. The subunit size of the purified aldolases, as determined by SDS-PAGE, was 42kDa for both aldolases. The isoenzymes were not inhibited by EDTA or affected by cysteine or potassium ions, implying that they belong to the class I group of aldolases, while other red algae are known to have one class I and one class II aldolase inhibited by EDTA. cDNA clones of the cytosolic and plastidic aldolases were isolated and sequenced. The gene for the cytosolic isoenzyme contained a 303bp untranslated leader sequence, while the gene for the plastidic isoenzyme exhibited a transit sequence of 56 amino-acid residues. Both isoenzymes showed about 48% homology in the deduced amino-acid sequences. A gene tree relates both aldolases to the basis of early eukaryotic class I aldolases. The phylogenetic relationship to other aldolases, particularly to cyanobacterial class II aldolases, is discussed.     

Morphology,fine structure,life cycle and phylogenetic analysis of Phyllosiphon arisari,a siphonous parasitic green alga

Phyllosiphon arisari Kühn (Phyllosiphonaceae, Chlorophyta) commonly occurs in Arisarum leaves in coastal Mediterranean areas of the Iberian Peninsula and Balearic islands. The genus Phyllosiphon was first considered to be a member of the Xanthophyceae but was later transferred to the chlorophytes. However, there are few data about its morphology, ultrastructure, ecology or phylogenetic affinities. In this paper we describe the morphology of Phyllosiphon, as studied in field material and in culture; the fine structure, analysed by transmission electron microscopy; and phylogenetic relationships, inferred from DNA sequences. The siphonous filaments were seen to divide and penetrate leaf tissues. The cytoplasm divided into spherical or subspherical sporocysts producing autospores inside. Cytoplasmic remains could be observed between autospores or on their cell walls. Phylogenetic analysis of 18S rDNA and 16S rDNA sequences showed that the closest relatives of Phyllosiphon are subaerial strains of Heterochlorella, Heveochlorella and Kalinella, demonstrating that Phyllosiphon should be transferred to Trebouxiophyceae. An evolution from unicells to a siphonous thallus, and from aerophytic to endophytic and parasitic habits, is proposed for Trebouxiophyceae.     

Antibiotics resistance of a red alga,Griffithsia japonica

To identify antibiotics suitable for stable transformation, we tested the resistance of a red alga,Griffithsia japonica Okamura, to four commonly used antibiotics. Very young germlings, with 1;3 cells, that germinated from the tetraspores were cultured for 40 d in a half PES medium containing kanamycin, streptomycin, hygromycin B, or phleomycin.G. japonica was highly sensitive to 1 μg mL^-1of phleomycin and g mL^-1of hygromycin B. However, it was resistant to kanamycin and low levels of streptomycin and hygromycin B. These results suggest that resistance genes for phleomycin or hygromycin can be used as selectable markers for transformation of G.japonica.     

The timing and manner of disassembly of the apparatuses for chloroplast and mitochondrial division in the red alga Cyanidioschyzon merolae

The timing and manner of disassembly of the apparatuses for chloroplast division (the plastid-dividing ring; PD ring) and mitochondrial division (the mitochondrion-dividing ring; MD ring) were investigated in the red alga Cyanidioschyzon merolae De Luca, Taddei and Varano. To do this, we synchronized cells both at the final stage of and just after chloroplast and mitochondrial division, and observed the rings in three dimensions by transmission electron microscopy. The inner (beneath the stromal face of the inner envelope) and middle (in the inter-membrane space) PD rings disassembled completely, and disappeared just before completion of chloroplast division. In contrast, the outer PD and MD rings (on the cytoplasmic face of the outer envelope) remained in the cytosol between daughter organelles after chloroplast and mitochondrial division. The outer rings started to disassemble and disappear from their surface just after organelle division, initially clinging to the outer envelopes at both edges before detaching. The results suggest that the two rings inside the chloroplast disappear just before division, and that this does not interfere with completion of division, while the outer PD and MD rings function throughout and complete chloroplast and mitochondrial division. These results, together with previous studies of C. merolae, disclose the entire cycle of change of the PD and MD rings. Received: 19 May 2000 / Accepted: 3 August 2000