Phycoerythrin evolution and diversification of spectral phenotype in marine Synechococcus and related picocyanobacteria

In marine Synechococcus there is evidence for the adaptive evolution of spectrally distinct forms of the major light harvesting pigment phycoerythrin (PE). Recent research has suggested that these spectral forms of PE have a different evolutionary history than the core genome. However, a lack of explicit statistical testing of alternative hypotheses or for selection on these genes has made it difficult to evaluate the evolutionary relationships between spectral forms of PE or the role horizontal gene transfer (HGT) may have had in the adaptive phenotypic evolution of the pigment system in marine Synechococcus. In this work, PE phylogenies of picocyanobacteria with known spectral phenotypes, including newly co-isolated strains of marine Synechococcus from the Gulf of Mexico, were constructed to explore the diversification of spectral phenotype and PE evolution in this group more completely. For the first time, statistical evaluation of competing evolutionary hypotheses and tests for positive selection on the PE locus in picocyanobacteria were performed. Genes for PEs associated with specific PE spectral phenotypes formed strongly supported monophyletic clades within the PE tree with positive directional selection driving evolution towards higher phycourobilin (PUB) content. The presence of the PUB-lacking phenotype in PE-containing marine picocyanobacteria from cyanobacterial lineages identified as Cyanobium is best explained by HGT into this group from marine Synechococcus. Taken together, these data provide strong examples of adaptive evolution of a single phenotypic trait in bacteria via mutation, positive directional selection and horizontal gene transfer.     

EFFECT OF SPECTRAL QUALITY ON GROWTH AND PIGMENTATION OF PICOCYANOBACTERIA1

The influence of spectral quality on growth and pigmentation was compared among five strains of marine and freshwater picocyanobacteria grown under the same photon flux density (28 μE · m^?2·s^?1). Growth and phycoerythrin (PE) concentration per unit carbon increased when marine Synechococcus WH7803 was grown under green light as compared to red light, but no change in phycocyanin concentration occurred. Marine Synechococcus strain 48B66 also showed greater levels of PE when grown under green light than under red light, but no concomitant growth increase occurred. Both strains thus exhibited Group II chromatic adaptation. Additionally, strain 48B66 increased the relative level of phycourobilin compared to phycoerythrobilin when grown under red light. In contrast, both marine and freshwater Synechococcus strains containing no PE showed decreased growth under green light. Chlorophyll a concentrations were greatest or among the greatest in all strains grown under green light. These results suggest that light quality, through its effects on growth rate, may be an important factor controlling the distribution and abundance of the various pigment types of Synechococcus.     

Chromatic adaptation in marine Synechococcus strains

Characterization of two genetically distinct groups of marine Synechococcus sp. strains shows that one, but not the other, increases its phycourobilin/phycoerythrobilin chromophore ratio when growing in blue light. This ability of at least some marine Synechococcus strains to chromatically adapt may help explain their greater abundance in particular ocean environments than cyanobacteria of the genus Prochlorococcus.     

Diversity and phylogeny of Baltic Sea picocyanobacteria inferred from their ITS and phycobiliprotein operons

Picocyanobacteria of the genus Synechococcus span a range of different colours, from red strains rich in phycoerythrin (PE) to green strains rich in phycocyanin (PC). Here, we show that coexistence of red and green picocyanobacteria in the Baltic Sea is widespread. The diversity and phylogeny of red and green picocyanobacteria was analysed using three different genes: 16S rRNA-ITS, the cpeBA operon of the red PE pigment and the cpcBA operon of the green PC pigment. Sequencing of 209 clones showed that Baltic Sea picocyanobacteria exhibit high levels of microdiversity. The partial nucleotide sequences of the cpcBA and cpeBA operons from the clone libraries of the Baltic Sea revealed two distinct phylogenetic clades: one clade containing mainly sequences from cultured PC-rich picocyanobacteria, while the other contains only sequences from cultivated PE-rich strains. A third clade of phycourobilin (PUB) containing strains of PE-rich Synechococcus spp. did not contain sequences from the Baltic Sea clone libraries. These findings differ from previously published phylogenies based on 16S rRNA gene analysis. Our data suggest that, in terms of their pigmentation, Synechococcus spp. represent three different lineages occupying different ecological niches in the underwater light spectrum. Strains from different lineages can coexist in light environments that overlap with their light absorption spectra.     

Clade-specific 16S ribosomal DNA oligonucleotides reveal the predominance of a single marine Synechococcus clade throughout a stratified water column in the Red Sea

Phylogenetic relationships among members of the marine Synechococcus genus were determined following sequencing of the 16S ribosomal DNA (rDNA) from 31 novel cultured isolates from the Red Sea and several other oceanic environments. This revealed a large genetic diversity within the marine Synechococcus cluster consistent with earlier work but also identified three novel clades not previously recognized. Phylogenetic analyses showed one clade, containing halotolerant isolates lacking phycoerythrin (PE) and including strains capable, or not, of utilizing nitrate as the sole N source, which clustered within the MC-A (Synechococcus subcluster 5.1) lineage. Two copies of the 16S rRNA gene are present in marine Synechococcus genomes, and cloning and sequencing of these copies from Synechococcus sp. strain WH 7803 and genomic information from Synechococcus sp. strain WH 8102 reveal these to be identical. Based on the 16S rDNA sequence information, clade-specific oligonucleotides for the marine Synechococcus genus were designed and their specificity was optimized. Using dot blot hybridization technology, these probes were used to determine the in situ community structure of marine Synechococcus populations in the Red Sea at the time of a Synechococcus maximum during April 1999. A predominance of genotypes representative of a single clade was found, and these genotypes were common among strains isolated into culture. Conversely, strains lacking PE, which were also relatively easily isolated into culture, represented only a minor component of the Synechococcus population. Genotypes corresponding to well-studied laboratory strains also appeared to be poorly represented in this stratified water column in the Red Sea.     

发光二极管光质对念珠藻葛仙米生长及生理生化特性的影响

利用发光二极管（LED）作为光源,以冷百荧光灯光作为对照,研究不同光质红光637 nm、绿光529 nm、蓝光453 nm、白光（400700） nm对念珠藻葛仙米生长和生理生化特性的影响。结果表明:在培养前期,红光促进藻蓝蛋白合成,而藻红蛋白合成受抑制;蓝光和绿光则促进藻蓝蛋白合成。在培养后期,红光处理有利于叶绿素a和类胡萝卜素积累,其含量分别达到干重的1.33%和0.24%;绿光、白光和冷白荧光培养物的相应色素的含量均约占1.0%和0.16%;蓝光培养物的相应色素含量分别仅为0.45%和0.11%。红光培养物的氨基酸含量达干重的23.1%,是对照的1.58倍。除蓝光外其他光质对还原糖的含量影响无显著差异。在培养过程中LED白光和冷白荧光培养物的平均相对生长速率分别约为其他色光培养物的1.3和1.5倍。       

Effect of Various Light Treatments on Chlorophyll Formation in Excised Potato Roots

Potato root tips were grown in cultures and the effect of blue, red, and white light on chlorophyll formation was studied. The roots grown in white light turned green in 4–6 weeks, whereas in blue or red light, green colour occasionally appeared at places. The chlorophyll contents, as determined by the spectrophotometeric method, were found to be maximum in unfiltered light followed by blue and red light. In white and blue light treatments chlorophyll a contents were higher than chlorophyll b, however in red light this was reversed. The results are compared with earlier experiments on chlorophyll formation in excised roots.     

THE EFFECT OF LIGHT QUALITY ON THE CARBON METABOLISM AND EXTRACELLULAR RELEASE OF CHLAMYDOMONAS REINHARDTII DANGEARD1

The influence of red, blue, green, and white light on growth and photosynthetic rates, carbon metabolism, and rates of release of extracellular compounds in the freshwater alga Chlamydomonas reinhardtii Dangeard was examined. Relative growth constants were 0.28, 0.32, 0.40, and 0.41 in green, white, blue, and red light, respectively. Photosynthetic rates were higher in white, blue, or red than in green light of the same intensity. More than 66% of the ¹⁴CO₂ assimilated by cells grown under blue or green light was incorporated into the ethanol-insoluble fraction, compared with about 50% in cells grown under white or red light. The percentage of sugars in this fraction was significantly higher in cells grown under green or red light than in cells cultured in white or blue light, while the percentage of proteins was highest in blue light. Light quality also influenced the composition of the ethanol-soluble fraction. The percentage of organic acids was highest in cells grown in green and white light, while amino acids were highest in blue and green cultures. The percentage of ethanol-soluble sugars was greatest in cultures grown in blue and red light. The percentage release of dissolved organic carbon into the medium was highest in white light and lowest in blue or red light. The nature of the extracellular products varied according to the quality of light under which the cells were cultured, but had no consistent relation to the nature or concentration or components in the ethanol-soluble fraction.     

光强与光质对银杏光合作用及黄酮苷与萜类内酯含量的影响

对2年生银杏（Ginkgo biloba L.)苗进行遮荫和光膜处理,测定光合速率及碳水化合物,银杏黄酮苷与萜类内酯的含量。光合速率在自然光下测定时从大到小依次为：黄膜＞蓝膜和红膜＞绿膜＞紫膜和白膜,在光膜下测定时为：黄膜＞红膜＞蓝膜、紫膜和白膜＞绿膜。光强和光质对碳水化合物含量有显著影响。光质对萜类内酯的生物合成和积累有影响,紫膜处理的银杏萜类内酯含量最高,为3.89mg/g,比白膜（对照） 高85．23％,其次是绿膜,为2．80mg/g。覆膜和蔗荫显著减少银杏黄酮苷含量,这可能与紫外辐射强度减弱有关。     

Effects of different LED sources on the growth and nitrogen metabolism of lettuce

Using a light-emitting diode (LED) as the light source, the effects of eight different light treatments [white light (control, W), purple light (P), blue light (B), red light (R), green light (G), yellow light (Y), red–blue light in a 9:1 ratio (9R/1B), and red–blue light in a 4:1 ratio (4R/1B)] on the growth, quality and nitrogen metabolism of lettuce were studied. The results showed that compared with the white light, the purple light, blue light, red light, and the red-blue light combination could all increase the biomass of the aboveground part of lettuce to various degrees, while green light and yellow light inhibited lettuce growth. Under blue light, the contents of soluble protein and flavonoid in lettuce were the highest; under red light, the soluble sugar content was the highest, while the contents of soluble protein, free amino acids, and vitamin C (VC) were relatively higher under the 4R/1B light condition. Compared with white light, the sources of purple, blue, and red lights as well as the red–blue light combination all significantly reduced nitrate accumulation in lettuce, and the activities of the nitrogen (N) metabolism-related enzymes such as nitrate reductase, nitrite reductase, glutamine synthetase, glutamate synthase, and glutamate dehydrogenase were increased to varying degrees. In contrast, the contents of nitrate and ammonium N were significantly accumulated in lettuce under green light, and the activities of relative enzymes were significantly reduced. Therefore, the purple light, blue light, and red–blue combination light sources could promote N assimilation and improve the aboveground biomass accumulation in lettuce by improving the activity of the N metabolism-related enzymes in lettuce. Particularly under the 4R/1B light source, the biomass, soluble protein, VC, and total amino acid content were rather high in lettuce, which indicated that the 4R/1B light source could better effectively improve the nutritional quality and promote the growth of lettuce, while yellow light and green light are not suitable to serve as direct sources in a plant factory. These results provide a certain theoretical basis for the regulation of the light environment in cultivation facilities.     

光质对中华盒形藻生长及生化组成的影响

中华盒形藻的增殖率在白光下最大,蓝光下次之,红光下最小。叶绿素、蛋白质的合成明显受蓝光促进,而红光下碳经合物含量增加。脂类含量在蓝光、红光下均有所下降。     

PHOTOREGULATION OF PHYCOBILISOME STRUCTURE DURING COMPLEMENTARY CHROMATIC ADAPTATION IN THE MARINE CYANOPHYTE PHORMIDIUM SP. C861

Changes in the molecular structure of phycobilisomes during complementary chromatic adaptation were studied in the marine cyanophyte Phormidium sp. C86. This strain forms phycoerythrin (PE)-less phycobilisomes under red light but synthesizes PE-rich phycobilisomes under green light. Analysis of phycobiliprotein composition and electron microscopic examination of phycobilisomes in ultra-thin sections of cells and of isolated phycobilisomes were performed for cells acclimated to red and green light, respectively. The structure of phycobilisomes formed under red light conditions was typically hemidiscoidal. Phycobilisomes in cells acclimated to green light were twice as large in size as those in cells acclimated to red light. This increase in phycobilisome size was a result of the increase in the molar ratio of antenna pigment (PE and phycocyanin) to allophycocyanin, from 3.5 to 11.3. Pigment composition and fine structure of phycobilisomes formed under green light were similar to those of “nonhemidiscoidal” phycobilisomes reported in Phormidium persicinum. These results suggest that changes occur not only in the molecular species of peripheral rods but also in the structure of rods and probably of cores in relation to their connection with rods during chromatic adaptation of Phormidium sp. C86.     

ACCLIMATION OF THE PHOTOSYNTHETIC APPARATUS OF PALMARIA PALMATA (RHODOPHYTA) TO LIGHT QUALITIES THAT PREFERENTIALLY EXCITE PHOTOSYSTEM I OR PHOTOSYSTEM II1

Acclimation of the photosynthetic apparatus to light absorbed primarily by phycobilisomes (which transfer energy predominantly to photosystem II) or absorbed by chlorophyll a (mainly present in the antenna of photosystem I) was studied in the macroalga Palmaria palmata L. In addition, the influence of blue and yellow light, exciting chlorophyll a and phycobilisomes, respectively, ivas investigated. All results were compared to a white light control. Complementary chromatic adaptation in terms of an enhanced ratio of phycoerythrin to phycocyanin under green light conditions was observed. Red light (mainly absorbed by chlorophyll a) and green light (mainly absorbed by phycobilisomes) caused an increase of the antenna system, which was not preferentially excited. Yellow and blue light led to intermediate states comparable to each other and white light. Growth was reduced under all light qualities in comparison to white light, especially under conditions preferably exciting phycobilisomes (green light-adapted algae had a 58% lower growth rate compared to white light-adapted algae). Red and blue light-adapted algae showed maximal photosynthetic capacity with white light excitation and significantly lower values with green light excitation. In contrast, green and yellow light-adapted algae exhibited comparable photosynthetic capacities at all excitation wavelengths. Low-temperature fluorescence emission analysis showed an increase of photosystem II emission in red light-adapted algae and a decrease in green light-adapted algae. A small increase of photosystem I emission teas also found in green light-adapted algae, but this was much less than the photosystem II emission increase observed in red light-adapted algae (both compared to phycobilisome emission). Efficiency of energy transfer from phycobilisomes to photosystem II was higher in red than in green light-adapted algae. The opposite was found for the energy transfer efficiency from phycobilisomes to photosystem I. Zeaxanthin content increased in green and blue light-adapted algae compared to red, white, and yellow light-adapted algae. Results are discussed in comparison to published data on unicellular red algae and cyanobacteria.     

Influence of IAA,TDZ, and light quality on asymbiotic germination,protocorm formation,and plantlet development of <Emphasis Type="Italic">Cyrtopodium glutiniferum</Emphasis> Raddi., a medicinal orchid

We investigated the influence of light quality on in vitro germination and protocorm formation, and the effect of indole-3-acetic acid (IAA) and thidiazuron (TDZ) on proliferation of protocorm-like bodies (PLBs) and development of plantlets of Cyrtopodium glutiniferum Raddi. Germination was faster under white and blue light, and highest under green light. The protocorm developed more rapidly under white, blue, and green light. Continuous darkness delayed seed germination and reduced protocorm formation. Among the plant growth regulators (PGRs) tested for multiplying PLBs, shoots, and roots from protocorms, IAA proved to be superior. TDZ was effective in inducing PLB fresh weight accumulation, but not morphogenesis, unlike IAA. This study indicated that C. glutiniferum seedlings can be produced in vitro using asymbiotic seed germination techniques. High germination rate and protocorm yield can be obtained by initially cultivating C. glutiniferum seeds on medium without growth regulators under white light, or under white light supplemented with green or blue light. This culture system complies with commercial and conservation requirements for rapid and low-cost propagation.     

光质对绿豆幼苗叶片超微弱发光及叶绿素含量的影响

以绿豆幼苗为试材,测定其叶片超弱发光(UBE)及叶绿素含量在不同光质条件下的变化,并探讨两者之间的关系.结果表明,生长在不同光质下绿豆幼苗叶片的UBE及延迟发光衰减参数1/P都随着其生长不断增强,且生长在白光下绿豆幼苗的UBE是生长在其他光质(红、黄、蓝、绿)下幼苗的2倍以上,而红光、黄光和绿光处理之间无显著差异;生长在白光下的绿豆幼苗叶片叶绿素含量显著高于红、黄、蓝、绿光处理幼苗,而红光和黄光处理又显著高于蓝光和绿光处理.研究发现,光质对绿豆幼苗叶片超弱发光和叶绿素含量影响相似,绿豆幼苗叶片超弱发光可能与叶绿体的发育和光合作用有关.     

Layer pullet preferences for light colors of light-emitting diodes

Light colors may affect poultry behaviors, well-being and performance. However, preferences of layer pullets for light colors are not fully understood. This study was conducted to investigate the pullet preferences for four light-emitting diode colors, including white, red, green and blue, in a lighting preference test system. The system contained four identical compartments each provided with a respective light color. The pullets were able to move freely between the adjacent compartments. A total of three groups of 20 Chinese domestic Jingfen layer pullets (54 to 82 days of age) were used for the test. Pullet behaviors were continuously recorded and summarized for each light color/compartment into daily time spent (DTS), daily percentage of time spent (DPTS), daily times of visit (DTV), duration per visit, daily feed intake (DFI), daily feeding time (DFT), feeding rate (FR), distribution of pullet occupancy and hourly time spent. The results showed that the DTS (h/pullet·per day) were 3.9±0.4 under white, 1.4±0.3 under red, 2.2±0.3 under green and 4.5±0.4 under blue light, respectively. The DTS corresponded to 11.7% to 37.6% DPTS in 12-h lighting periods. The DTV (times/pullet·per day) were 84±5 under white, 48±10 under red, 88±10 under green and 94±8 under blue light. Each visit lasted 1.5 to 3.2 min. The DFI (g/pullet·per day) were 27.6±1.7 under white, 7.1±1.6 under red, 15.1±1.1 under green and 23.1±2.0 under blue light. The DFT was 0.18 to 0.65 h/pullet·per day and the FR was 0.57 to 0.75 g/min. For most of the time during the lighting periods, six to 10 birds stayed under white, and one to five birds stayed under red, green and blue light. Pullets preferred to stay under blue light when the light was on and under white light 4 h before the light off. Overall, pullets preferred blue light the most and red light the least. These findings substantiate the preferences of layer pullets for light colors, providing insights for use in the management of light-emitting diode colors to meet pullet needs.     

The effect of different wavelengths of light during incubation on the development of rhythmic pineal melatonin biosynthesis in chick embryos

Rhythmic pineal melatonin biosynthesis develops in chick embryos incubated under a light (L)-dark (D) cycle of polychromatic white light. The spectral sensitivity of the embryonic pineal gland is not known and was investigated in this study. Broiler breeder eggs (Ross 308, n=450) were incubated under white, red, green or blue light under the 12L : 12D cycle. Melatonin was measured in extracts of pineal glands by radioimmunoassay. The daily rhythm of pineal melatonin levels in 20-day-old chick embryos was confirmed during the final stages of embryonic life under all four wavelengths of light with expected higher concentrations during dark- than light-times. The highest pineal melatonin levels were determined in chick embryos incubated under red and white light and lower levels under green light. The incubation under blue light resulted in the lowest melatonin biosynthesis. Pineal melatonin concentrations increased substantially on post-hatching day two compared with pre-hatching levels and we did not find differences between birds incubated and kept in either white or green light. Our results demonstrate a selective sensitivity of the chick embryo pineal gland to different wavelengths of light. Rhythmic melatonin production is suggested as a possible mechanism, which transfers information about the quality of ambient light to the developing avian embryo.     

光质对水稻幼苗蛋白质、氨基酸含量的影响

蓝光对水稻幼苗可溶性蛋白积累的促进效应,在幼苗生长的初期比较明显;第5天,幼苗的可溶性蛋白质、蛋白氮、非蛋白氮以及Asp、Asn、Glu、Gln等游离氨基酸含量都远远高于白光或红光的处理。随着苗龄的增加,蓝光的促进作用减弱,到第17天,各项指标都低于白光处理的幼苗。红光处理的幼苗可溶性蛋白始终低于白光或蓝光的处理,其 Asn、Gln 两种酰胺含量在第10天以后明显高于同期的白光或蓝光的处理。