DNA Fingerprinting of Pearls to Determine Their Origins

We report the first successful extraction of oyster DNA from a pearl and use it to identify the source oyster species for the three major pearl-producing oyster species Pinctada margaritifera, P. maxima and P. radiata. Both mitochondrial and nuclear gene fragments could be PCR-amplified and sequenced. A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay in the internal transcribed spacer (ITS) region was developed and used to identify 18 pearls of unknown origin. A micro-drilling technique was developed to obtain small amounts of DNA while maintaining the commercial value of the pearls. This DNA fingerprinting method could be used to document the source of historic pearls and will provide more transparency for traders and consumers within the pearl industry.     

Polysaccharides of Calcareous Algae and Their Effect on the Calcification Process

The composition and structure of polysaccharides from several groups of calcareous algae (including calcareous cyanobacteria), which differ in the calcification mode (extracellular, cell wall, or intracellular), are reviewed. Two families of marine algae, Corallinaceae (Rhodophyta) and Coccolithophoraceae (Prymnesiophyta = Haptophyta), are considered in detail; they exhibit the cell wall and intracellular calcification modes, respectively, and synthesize unusual polysaccharides that seem to directly participate in the calcification process.     

藻类对垃圾填埋场渗滤液的净化

采用PCR及序列测定的方法,对两个分别分离自广州市李坑垃圾填埋场的渗滤液收集塘以及广州市郊的一个普通池塘的藻类种群的rDNA ITS区进行了序列的测定和分析,结果证实两者均为蛋白核小球藻,分别记作Chlorella pyrenoidosa(LK)和Chlorella pyrenoidosa(P)。将上述两个藻类种群的纯培养液分别接种至一系列不同浓度的垃圾渗滤液中,以研究它们在渗滤液中的生长,对渗滤液的耐性以及对渗滤液中污染物的去除等差异。结果表明,藻类的生长在10％的渗滤液中都得到一定的促进,而在更高浓度的渗滤液中则受到抑制,但C.pryenoidosa(LK)在经过一段时间的适应后,对30％的渗滤液表现出较强的耐性。藻类的生长使垃圾渗滤液中的NH3－N,PO4－P和COD等污染物的含量显著下降,而NO3－N含量下降不明显。     

Plastids and protein targeting.

Plastids with two bounding membranes--as exemplified by red algae, green algae, plants, and glaucophytes--derive from primary endosymbiosis; a process involving engulfment and retention of a cyanobacterium by a phagotrophic eukaryote. Plastids with more than two bounding membranes (such as those of euglenoids, dinoflagellates, heterokonts, haptopytes, apicomplexa, cryptomonads, and chlorarachniophytes) probably arose by secondary endosymbiosis, in which a eukaryotic alga (itself the product of primary endosymbiosis) was engulfed and retained by a phagotroph. Secondary endosymbiosis transfers photosynthetic capacity into heterotrophic lineages, has apparently occurred numerous times, and has created several major eukaryotic lineages comprising upwards of 42,600 species. Plastids acquired by secondary endosymbiosis are sometimes referred to as "second-hand." Establishment of secondary endosymbioses has involved transfer of genes from the endosymbiont nucleus to the secondary host nucleus. Limited gene transfer could initially have served to stabilise the endosymbioses, but it is clear that the transfer process has been extensive, leading in many cases to the complete disappearance of the endosymbiont nucleus. One consequence of these gene transfers is that gene products required in the plastid must be targeted into the organelle across multiple membranes: at least three for stromal proteins in euglenoids and dinoflagellates, and across five membranes in the case of thylakoid lumen proteins in plastids with four bounding membranes. Evolution of such targeting mechanisms was obviously a key step in the successful establishment of each different secondary endosymbiosis. Analysis of targeted proteins in the various organisms now suggests that a similar system is used by each group. However, rather than interpreting this similarity as evidence of an homologous origin, I believe that targeting has evolved convergently by combining and recycling existing protein trafficking mechanisms already existing in the endosymbiont and host. Indeed, by analyzing the multiple motifs in targeting sequences of some genes it is possible to infer that they originated in the plastid genome, transferred from there into the primary host nucleus, and subsequently moved into the secondary host nucleus. Thus, each step of the targeting process in "second-hand" plastids recapitulates the gene's previous intracellular transfers.     

Changes of Plastids Mitochondria and Their DNA in the Egg Cell Before and After Fertilization in Pharbitis

The ultrastructure and cytoplasmic DNA in the egg cell and zygote of Pharbitis purpurea, (L.) Voyght and P. limbata Lindl. which were studied with electron microscopy and DNA epifiuorescence microscopy. The egg cell before fertilization was highly vacuolated with only a few cytoplasmic plastids and mitochondria. Plastids were spherical and/or rod- shaped containing 1 ～ 2 large starch grains. Most of the mitochondria were cup and/or circular. The cytoplasm in the zygote was much more abundant than that in the egg cell. The number of plastids and their electronic density were greatly increased, in most of which containing osmiophilic bodies. The mitochondria were rich and spherical-shaped in the zygote. Two types of cytoplasmic DNA nucleoids were detected in the egg cell, the more abundant one being big and circle-shaped and the other dot-shaped. Only dot-shaped nucleoids were present in the zygote. The content of nucleoids in the zygote was much less than that in the egg cell. Authors propose that some cytoplasmic DNA may degenerate after fertilization. The ultrastructural characteristics of the egg cell and the reduction of cytoplasmic DNA in the zygote may related to the mechanisms of plastid unipaternal inheritance in Pharbitis.     

Extracellular Alkaline Phosphatase in Multicellular Marine Algae and Their Utilization of Glycerophosphate

The production of extracellular alkaline phosphatase by multicellular marine algae in axenic culture has been investigated. The algae studied were five species of Rhodophyta: Asterocytis ramosa, Goniotrichum elegans, Nemalion helminthoides, Polysiphonia urceolata and Rhodosorus marinus; and one species of Phaeophyta: Ecrocarpus confervoides. The extent of enzyme activity varies from one species to another. It also varies with the phosphorus conditions under which the alga is grown. The pattern of glycerophosphate utilization suggests that this type of compound is not taken up directly by the alga but split by the external enzyme before uptake of the phosphate-ion only. The enzyme performs its action outside the organism and appears both associated with the cells and free in the surrounding water. Assays with culture filtrate of Asterocytis and Ectocarpus show that the enzyme is an unspecific phosphomonoesterase with optimum activity far to the alkaline side. It is activated by Zn²⁺.     

Macromolecular Physiology of Plastids

The composition and amount of carotenoid pigments were determined in etiolated seedling leaves of 6 barley (Hordeum vulgare L.) mutants, comprising 1 xantha and 5 tigrina mutants. All mutants had on a mole basis approximately the same content of carotenoids as the wild type. The mutants xan-u²¹, tig-n³², and tig-³³ contained significantly higher amounts of carotenes than the wild type, ranging from 32 to 68% of the total carotenoid content as compared to the 4–8% found in the wild type. In the mutants tig-b²³ and tig-o³⁴, only a slight increase in the amount of carotenes was notable. The carotene content and composition in tig-d¹² was indistinguishable from that of the wild type. The carotenes extracted from xan-u²¹, tig-b²³, tig-n³², tig-³³, and tig-o³⁴ were characterized by adsorption chromatography and spectrophotometry. Mutant xan-u²¹ is in the dark blocked in β-carotene synthesis, and accumulates the aliphatic polyenes: phytofluene, proneurosporene, poly-cis-lycopenes, neo-lycopene and lycopene. The other four mutants synthesize β-carotene, but accumulate in addition various higher saturated carotenes, the main components being ζ-carotene in tig-b²³, a lycopenic pigment in tig-n³² and tig-³³, and lycopene in tig-o³⁴. Accumulation of higher saturated carotenes appears correlated with specific aberrations of the membrane structure in plastids. The regulation of carotene and protochlorophyllide syntheses in etioplasts are closely linked as shown by the single gene mutants which affect both pathways. However, several mutants have been identified which cause defects in protochlorophyllide synthesis only.     

Plastids in parasites of humans

It has recently emerged that malarial, toxoplasmodial and related parasites contain a vestigial plastid (the organelle in which photosynthesis occurs in plants and algae). The function of the plastid in these obligate intracellular parasites has not been established. It seems likely that modern apicomplexans derive from photosynthetic predecessors, which perhaps formed associations with protists and invertebrates and abandoned autotrophy in favour of parasitism. Recognition of a third genetic compartment in these parasites proffers alternative strategies for combating a host of important human and animal diseases. It also poses some fascinating questions about the evolutionary biology of this important group of pathogens.     

Cytological Basis of Plastid Inheritance in Phaseolus vulgaris-Investigations of Plastids,Mitochondria and Their DNA Nucleoids During Pollen Development

Electron microscopic and DNA fluorescence microscopic observations of the plastids, mitochondria and their DNA in the developing pollen of Phaseolus vulgaris L. have demonstrated that the male plastids were excluded during microspore mitosis. The formed generative cell was free of plastids because of regional localization of plastids in early developing microspore and the extremely unequal distribution during division. The fluorescence observations of DNA showed that cytoplasmic (plastid and mitochondria) nucleoids degenerated and disappeared during the development of microspore/pollen, and were never presented in the generative cell at different development stages. These results provided precise cytological evidence of maternal plastid inheritance in Phaseolus vulgaris, which was not in accord with the biparental plastid inheritance identified from early genetic analysis. Based on authors' previous observations in a variety of common bean that the organelle DNA of male gamete was completely degenerated, the early genetic finding of the biparental plastid inheritance was unlikely to be effected by genotypic difference. Thus those biparental plastid inheritance might be caused by occational male plastid transmission, and plastid uniparental maternal inheritance was the species character of Phaseolus vulgaris.     

The Fine Structure of Avocado Plastids

Ultrastructural studies of both young and harvest-ripe avocadofruits have established that the skin and outer green layersof flesh contain chloroplasts with an extensive thylakoid system.Etioplasts occur in the yellow flesh adjacent to the stone.The pale-green flesh contains plastids, intermediate betweenchloroplasts and etioplasts, which have prominent prolamellarbodies from which radiate grana. When segments of both the yellow and pale-green flesh of maturefruit (7 cm diam.) are cultured in the light their prolamellarbodies do not disperse although there is a change in their crystallinity.The palegreen tissues of immature (4 mm and 2 cm diam.) fruitsalso contain etioplasts but on culturing these differentiateinto chloroplasts. Both chlorophyll content and the ratio ofchlorophyll a to b varied in the different tissues of youngand mature fruits.     

Parents' Cultural Belief Systems: Their Origins, Expressions, and Consequences

Parents' Cultural Belief Systems: Their Origins, Expressions, and Consequences. Sara Harkness and Charles M. Super, eds. New York: The Guilford Press, 1996. 558 pp.     

Origins of the Xylella fastidiosa Prophage-Like Regions and Their Impact in Genome Differentiation

Xylella fastidiosa is a Gram negative plant pathogen causing many economically important diseases, and analyses of completely sequenced X. fastidiosa genome strains allowed the identification of many prophage-like elements and possibly phage remnants, accounting for up to 15% of the genome composition. To better evaluate the recent evolution of the X. fastidiosa chromosome backbone among distinct pathovars, the number and location of prophage-like regions on two finished genomes (9a5c and Temecula1), and in two candidate molecules (Ann1 and Dixon) were assessed. Based on comparative best bidirectional hit analyses, the majority (51%) of the predicted genes in the X. fastidiosa prophage-like regions are related to structural phage genes belonging to the Siphoviridae family. Electron micrograph reveals the existence of putative viral particles with similar morphology to lambda phages in the bacterial cell in planta. Moreover, analysis of microarray data indicates that 9a5c strain cultivated under stress conditions presents enhanced expression of phage anti-repressor genes, suggesting switches from lysogenic to lytic cycle of phages under stress-induced situations. Furthermore, virulence-associated proteins and toxins are found within these prophage-like elements, thus suggesting an important role in host adaptation. Finally, clustering analyses of phage integrase genes based on multiple alignment patterns reveal they group in five lineages, all possessing a tyrosine recombinase catalytic domain, and phylogenetically close to other integrases found in phages that are genetic mosaics and able to perform generalized and specialized transduction. Integration sites and tRNA association is also evidenced. In summary, we present comparative and experimental evidence supporting the association and contribution of phage activity on the differentiation of Xylella genomes.     

Origin and Evolution of Plastids and Photosynthesis in Eukaryotes

Recent progress in understanding the origins of plastids from endosymbiotic cyanobacteria is reviewed. Establishing when during geological time the endosymbiosis occurred remains elusive, but progress has been made in defining the cyanobacterial lineage most closely related to plastids, and some mechanistic insight into the possible existence of cryptic endosymbioses perhaps involving Chlamydia-like infections of the host have also been presented. The phylogenetic affinities of the host remain obscure. The existence of a second lineage of primary plastids in euglyphid amoebae has now been confirmed, but the quasipermanent acquisition of plastids by animals has been shown to be more ephemeral than initially suspected. A new understanding of how plastids have been integrated into their hosts by transfer of photosynthate, by endosymbiotic gene transfer and repatriation of gene products back to the endosymbiont, and by regulation of endosymbiont division is presented in context.Photosynthesis is biology’s equivalent of alchemy converting a common substance (CO₂) into a precious one (reduced carbon compounds rich in chemical energy). Freely available light energy is initially converted to precious chemical energy in the form of ATP. This energy, and the reducing power generated by splitting water molecules to release electrons, is used to fix carbon from atmospheric CO₂ and generate reduced carbon compounds that underpin the biosphere. It is estimated that plants and algae convert 258 billion tons of carbon dioxide into biomass by photosynthesis annually (Geider et al. 2001). Microfossils in ancient stromatolites indicate that cyanobacterium-like organisms had invented this process—or an early, perhaps nonoxygenic, version of it—at least 3.5 byo (billions of years old) (Lowe 1980; Walter et al. 1980; Schopf 1993). These photosynthetic prokaryotes substantially predate eukaryotes, which emerged much later (Rasmussen et al. 2008; Koonin 2010). The common ancestor of all eukaryotes entered into an endosymbiotic partnership with an α-proteobacterium that evolved into the mitochondrion, now the site of aerobic respiration in most eukaryotes (Gray 2012); animals and fungi are heterotrophic descendants of this partnership. Another lineage, which eventually produced the plants, entered into a second endosymbiotic partnership, this time with a cyanobacterium, which transplanted photosynthetic alchemy into eukaryotes to create plastids (Gray and Archibald 2012). This review will highlight recent progress in our understanding of the origin and evolution of plastids.     

Plastids in sieve elements and their companion cells

Summary Plastids have been identified in the sieve elements and/or companion cells of 14 monocotyledon species. In contrast to earlier reports, plastids are present in the sieve elements of Smilax and the companion cells of Tradescantia. The development and fine structure of the sieve-element plastids in Smilax do not differ from the type found in all of the 230 angiosperm species we have studied so far contain prominent plastids. The companion cells are easily identified by their specialized plasmatic connections with the sieve elements. The leucoplasts in the companion cells of Tradescantia are identical with those reported for many angiosperms.     

Vesicles Are Persistent Features of Different Plastids

Peripheral vesicles in plastids have been observed repeatedly, primarily in proplastids and developing chloroplasts, in which they are suggested to function in thylakoid biogenesis. Previous observations of vesicles in mature chloroplasts have mainly concerned low temperature pretreated plants occasionally treated with inhibitors blocking vesicle fusion. Here, we show that such vesicle‐like structures occur not only in chloroplasts and proplastids, but also in etioplasts, etio‐chloroplasts, leucoplasts, chromoplasts and even transforming desiccoplasts without any specific pretreatment. Observations are made both in C3 and C4 species, in different cell types (meristematic, epidermis, mesophyll, bundle sheath and secretory cells) and different organs (roots, stems, leaves, floral parts and fruits). Until recently not much focus has been given to the idea that vesicle transport in chloroplasts could be mediated by proteins, but recent data suggest that the vesicle system of chloroplasts has similarities with the cytosolic coat protein complex II system. All current data taken together support the idea of an ongoing, active and protein‐mediated vesicle transport not only in chloroplasts but also in other plastids, obviously occurring regardless of chemical modifications, temperature and plastid developmental stage.      

Complemental Effect of Osmotic Stabilizers and Their Roles in Degradation Cell Walls of Blue-Green Algae

The compound osmotic stabilizers consisted of several salt solutions exerted a greater effect on the isolation of blue-green algae spheroplasts than a single salt solution. However, the effect of compound osmotic stabilizers on the spheroplast stability could be multiphasic. Some osmotic stabilizers, such as the solution of (NH4) 2C4H406, (NH4) 2SO4 and MgSO4, exerted degradation on cell walls of the blue-green alga; among which the (NH4) 2C4H406 solution (0.15 mol/L) had the greatest degradation resulting in formation of spheroplasts. The spheroplasts were sensitive to hypotonic condition but were less transparent.