Daily production and photosynthetic characteristics of Nostoc flagelliforme grown under ambient and elevated CO2 conditions

Diurnal photosynthesis of Nostoc flagelliforme was investigated at varied levels of CO2 concentrations and desiccation in order to estimate the effects of enriched CO2 and watering on its daily production. Photosynthetic activity was closely correlated with the desiccated status of the algal mats, increased immediately after watering, reached a maximum at moderate water loss, and then declined with further desiccation. Increased CO2 concentration enhanced the diurnal photosynthesis and raised the daily production. Watering twice per day enhanced the daily production due to prolonged period of active photosynthesis. The values of daily net production were 1321280 mumol CO2 g (d. wt)(-1) d(-1), corresponding to about 0.6-6.1% daily increase in dry weight. High-CO2-grown mats required higher levels of photon flux density to saturate the alga's photosynthesis in air. Air-grown mats showed higher photosynthetic affinity for CO2 and higher levels of dark respiration compared with high-CO2-grown samples.

Photosynthetic bicarbonate utilization by a terrestrial cyanobacterium, Nostoc flagelliforme (Cyanophyceae)

The photosynthetic characteristics of the terrestrial cyanobacterium, Nostoc flagelliforme, after complete recovery by rewetting, was investigated to see whether it could use bicarbonate as the external inorganic carbon source when submerged. The photosynthesis-pH relationship and high pH compensation point suggested that the terrestrial alga could use bicarbonate to photosynthesize when submerged. The photosynthetic oxygen evolution rates were significantly inhibited in Na+-free and Na+ + Li+ media but were not affected by the absence of Cl-, implying that the bicarbonate uptake was associated with Na+/HCO3- symport rather than Cl-/HCO3- exchange system.

Influence of CO2, light and watering on growth of Nostoc flagelliforme mats

The terrestrial blue-green alga (cyanobacterium), Nostoc flagelliforme, was cultured in air at various levels of CO2, light and watering to see their effects on its growth. The alga showed the highest relative growth rate at the conditions of high CO2 (1500 ppm), high light regime (219-414 mu mol m(-2)s(-1)) and twice daily watering, but the lowest rate at the conditions of low light (58-114 mu mol m(-2)s(-1)) and daily twice watering. Increased watering had little effect on growth rate at 350 ppm CO2, but increased by about 70% at 1500ppm CO2 under high light conditions. It was concluded that enriched CO2 could enhance the growth of N. flagelliforme when sufficient light and water was supplied.

Light dependency of the photosynthetic recovery of Nostoc flagelliforme

PS II photochemical efficiency (F-v/F-m) of Nostoc flagelliforme was examined after rewetting in order to investigate the light-dependency of its photosynthetic recovery. F-v/F-m was not detected in the dark, but was immediately recognized in the light. Different levels of light irradiation (4, 40 and 400 mu mol photon m(2) s(-1)) displayed different effects on the recovery process of photosynthesis. The intermediate level led to the best recovery of photochemical efficiency; the low light required longer and the high light inhibited the extent of the recovered efficiency. It was concluded that the photosynthetic recovery of N. flagelliforme is both light-dependent and influenced by photon flux density.

Effect of wind speed on loss of water from Nostoc flagelliforme colonies

The effects of wind speed on loss of water from N. flagelliforme colonies were investigated indoors in an attempt to assess its ecological significance in field. Wind enhanced the process of waterless; the half-time of desiccation at wind speeds of 2.0 and 3.4 m s(-1) was, respectively, shortened to one-third and one-fifth at 20 degrees C and, to one-sixth and one-eighth at 27 degrees C that of still air. Photosynthetic efficiency was not affected before the wet alga lost about 50% water.

Cytoglobosins A-G, Cytochalasans from a Marine-Derived Endophytic Fungus, Chaetomium globosum QEN-14

Financial support from the Ministry of Science and Technology of China (2010CB833802 and 2007AA09Z446) and from the National Science Foundation of China (30910103914) is gratefully acknowledged.

The integrative expression of GUS gene driven by FCP promoter in the seaweed Laminaria japonica (Phaeophyta)

In this study, the background activity of beta-glucuronidase (GUS) was analyzed histochemically and fluorometrically in the negative control of Laminaria japonica (Phaeophyta) thalli, showing low level of activity. GUS gene transformation without selectable gene in L. japonica was performed using four different promoters, i.e., Cauliflower mosaic virus 35S promoter (CaMV35S) from cauliflower mosaic virus, ubiquitin promoter (UBI) from maize, adenine-methyl transfer enzyme gene promoter (AMT) from virus in green alga Chlorella, and fucoxanthin chlorophyll a/c-binding protein gene promoter (FCP) from diatom Phaeodactylum tricornutum. The GUS transient activity was determined fluorometrically after bombarding sliced parthenogenetic sporophytes explants, and it was found that the activity resulting from CaMV35S and FCP promoters (in 114.3 and 80.6 pmol MU min(-1) (mg protein)(-1), respectively) was higher than for the other two promoters. The female gametophytes were bombarded and regenerated parthenogenetic sporophytes. FCP was the only promoter that resulted in detectable GUS chimeric expression activity during histochemical staining and polymerase chain reaction. Results of Southern blot showed that GUS gene was integrated with the L. japonica genome.

Cloning and characterization of beta-carotene ketolase gene promoter in Haematococcus pluvialis

The unicellular green alga Haematococcus pluvialis accumulates a highly valuable ketocarotenoid, astaxanthin, under various environmental stresses. beta-carotene ketolase (BKT) plays a key role in astaxanthin biosynthesis in H. pluvialis. In this paper, an approximate 700 bp 5'-flanking region of the bkt gene containing a putative promoter was cloned through walking upstream. The results of the sequence analysis showed that this bkt 5'-flanking region might have cis-acting elements such as sterol regulatory element (SRE-1)-like motifs, the C-repeat/dehydration responsive element (DRE) and al-3 proximal element (APE)-like motifs, except for typical TATA and CCAAT boxes. The results of the P-galactosidase assay and the transient expression of lacZ driven by a series of sequential deletions revealed that a minimal promoter-like region might exist from -630 to -408 bp, and the highest promoter activity was observed to span the positions from -630 to -308 bp. The results of the site-directed mutagenesis of a C-repeat/DRE and two APE-like motifs in a promoter-like region (-630 to -308 bp) suggested that two APE-like motifs might be essential for transcriptional control of the bkt gene.

Establishment of a micro-particle bombardment transformation system for Dunaliella saliva

In this study, we chronicle the establishment of a novel transformation system for the unicellular marine green alga, Dunaliella salina. We introduced the CaMV35S promoter-GUS construct into D. saliva with a PDS1000/He micro-particle bombardment system. Forty eight h after transformation, via histochemical staining, we observed the transient expression of GUS in D. salina cells which had been bombarded under rupture-disc pressures of 450 psi and 900 psi. We observed no GUS activity in either the negative or the blank controls. Our findings indicated that the micro-particle bombardment method constituted a feasible approach to the genetic transformation of D. salina. We also conducted tests of the cells' sensitivity to seven antibiotics and one herbicide, and our results suggested that 20 mu g/ ml of Basta could inhibit cell growth completely. The bar gene, which encodes for phosphinothricin acetyltransferase and confers herbicide tolerance, was introduced into the cells via the above established method. The results of PCR and PCR-Southern blot analyses indicated that the gene was successfully integrated into the genome of the transformants.

Comparative studies on the efficiency of energy transfer of two R-phycoerythrin-C-phycocyanin conjugates constructed from sodium periodate and glutaraldehyde respectively

The C-phycocyanin and the R-phycoerythrin were purified from the blue-green alga Spirulina platensis and red alga Polysiphonia urceolata respectively. Both sodium periodate and glutaraldehyde are effective coupling agents being capable of constructing the R-phycoerythrin-C-phycocyanin conjugate, which was also called phycobiliproteins energy transfer model. The two artificial conjugates constructed with different methods were purified by Sephadex G-200 chromatography respectively. Spectra analysis indicated that energy transfer occurred in the two conjugates. The conjugate with sodium periodate had the higher efficiency of energy transfer than that with glutaraldehyde conjugate.

Three-stage transformation of chlorophyll transient fluorescence pattern under sustained dehydration and the discovery of critical water content in seaweeds

The chlorophyll fluorescence kinetics of marine red alga Grateloupia turutunt Yamada, green alga Ulva pertusa Kjellm and brown alga Laminaria japonica Aresch during natural sustained dehydration were monitored and investigated. The pulse amplified modulation (PAM) system was used to analyze the distinct fluorescence parameters during thallus dehydration. Results proved that the fluorescence kinetics of different seaweed all showed three patterns of transformation with sustained water loss. These were: 1) peak kinetic pattern (at the early stage of dehydration fluorescence enhanced and quenched subsequently, representing a normal physiological state). 2) plateau kinetic pattern (with sustained water loss fluorescence enhanced continuously but quenching became slower, finally reaching its maximum). 3) Platform kinetic pattern (fluorescence fell and the shape of kinetic curve was similar to plateau kinetic pattern). A critical water content (CWC) could be found and defined as the percentage of water content just prior to the fluorescence drop and to be a significant physiological index for evaluation of plant drought tolerance. Once thallus water content became lower than this value the normal peak pattern can not be recovered even through rehydration, indicating an irreversible damage to the thylakoid membrane. The CWC value corresponding to different marine species were varied and negatively correlated with their desiccation tolerance, for example. Laminaria japonica had the highest CWC value (around 90%) and the lowest dehydration tolerance of the three. In addition, a fluorescence "burst" was found only in red algae during rehydration. The different fluorescence parameters F-o, F-v and F-v, F-m were measured and compared during water loss. Both F-o and F-v increased in the first stage of dehydration but F-v/F-m. kept almost constant. So the immediate response of in vivo chlorophyll fluorescence to dehydration was an enhancement. Later with sustained dehydration F-o increased continuously while F-v decreased and tended to become smaller and smaller. The major changes in fluorescence (including fluorescence drop during dehydration and the burst during rehydration) were all attributed to the change in F-o instead of F-v This significance of F-o indicates that it is necessary to do more research on F-o as well as on its relationship with the state of thylakoid membrane.

A new model of phycobilisome in Spirulina platensis

Phycobilisomes (PBS) were isolated from blue-green alga Spirulina platensis. Scanning tunneling microscope was used to investigate the three-dimensional structure of PBS deposited on freshly cleaved highly oriented pyrolytic graphite (HOPG) in ambient condition at room temperature. The results showed that the rods of PBS radiated from the core to different directions in the space other than arrayed in one plane, which was different from the typical hemi-discoidal model structure. The diameter of PBS was up to 70 nm, and the rod was approximately 50 nm in length. Similar results were observed in Langmuir-Blodgett (LB) film of PBS. The dissociated PBS could reaggregate into rod-like structures and easily form two-dimensional membrane while being absorbed on HOPG, however, no intact PBS was observed. The filling-space model structure of PBS in Spirulina platensis with STM from three-dimensional real space at nanometer scale was found, which showed that this new structural model of PBS surely exists in blue-green algae and red algae. The function of this structural model of PBS was also discussed.

Study on the structure of C-phycocyanin in Spirulina platensis with scanning tunneling microscope

The C-phycocyanin (C-PC) trimmer was isolated from the blue-green alga Spirulina platensis, and scanning tunnelling microscope (STM) was used to investigate its structure, High resolution STM images of C-PC were obtained. From the STM images, it could be observed that the C-PC molecules were disk-like in shape and the subunits of C-PC arranged in ring-like pattern with a channel in the center. After filter treatment, the folding of the polypeptide chains could be. seen clearly. This is the first time to observe directly the topography of phycobiliprotein, and the results showed STM to be a powerful tool for the structural study of phycobiliproteins.

Influence of albumen on aggregation and O-2 evolution of protoplasm from Bryopsis hypnoides Lamourou

The extruded protoplasm from the coenocytic green alga, Bryopsis hypnoides Lamouroux, was able to reform a cell wall and develop further into a mature alga in seawater. In this paper, the influence of albumen on the ability of aggregation and on the photosynthesis of protoplasm was examined. Results show that the protoplasm of B. hypnoides could aggregate in either albumen or chicken egg, which is similar to that in seawater. However unlike in seawater, the aggregation from B. hypnoides in albumen and chicken egg failed to develop into a mature individual. Interestingly, the protoplasm of B. hypnoides could maintain its photosynthetic O-2 evolution in albumen and chicken egg, while the time in chicken egg was longer than that in albumen.

Molecular cloning, characterization and evolutionary analysis of phytoene desaturase (PDS) gene from Haematococcus pluvialis

Phytoene desaturase is one of the most important enzymes necessary for the biosynthesis of carotenoids in some cyanobacteria, green algae and plants. In this study, genomic DNA and cDNA of pds were cloned from unicellular green alga Haematococcus pluvialis strain323 using PCR and RT-PCR methods. The cDNA was cloned into plasmid pET-28a and efficiently expressed in Escherichia coli BL21. The complete genomic PDS gene of H. pluvialis, 3.3 kb in size, included eight exons and seven introns. To locate transcriptional regulation elements, an approximate 1 kb of 5'-flanking region was isolated by genome-walking method. Results of bioinformatic analysis showed several putative cis-elements e.g. the ABRE motif (abscisic acid responsive element), the C-repeat/DRE (dehydration responsive element) motif and the GCN4 motif were located in 5'-flanking region of pds. Results of phylogenetic analyses reveal that different sources of PDS genes form a separate clade, respectively, with 100% bootstrap support. Moreover, a maximum likelihood approach was employed to detect evidence of positive selection in the evolution of PDS genes. Results of branch-site model analysis suggest that 7.9% of sites along the green algal branch are under positive selection, and the PDS gene in green algae exhibits a different evolutionary pattern from its counterparts in cyanobacteria and plants.