Chimeric plastid proteome in the Florida "red tide" dinoflagellate Karenia brevis

Current understanding of the plastid proteome comes almost exclusively from studies of plants and red algae. The proteome in these taxa has a relatively simple origin via integration of proteins from a single cyanobacterial primary endosymbiont and the host. However, the most successful algae in marine environments are the chlorophyll c-containing chromalveolates such as diatoms and dinoflagellates that contain a plastid of red algal origin derived via secondary or tertiary endosymbiosis. Virtually nothing is known about the plastid proteome in these taxa. We analyzed expressed sequence tag data from the toxic "Florida red tide" dinoflagellate Karenia brevis that has undergone a tertiary plastid endosymbiosis. Comparative analyses identified 30 nuclear-encoded plastid-targeted proteins in this chromalveolate that originated via endosymbiotic or horizontal gene transfer (HGT) from multiple different sources. We identify a fundamental divide between plant/red algal and chromalveolate plastid proteomes that reflects a history of mixotrophy in the latter group resulting in a highly chimeric proteome. Loss of phagocytosis in the "red" and "green" clades effectively froze their proteomes, whereas chromalveolate lineages retain the ability to engulf prey allowing them to continually recruit new, potentially adaptive genes through subsequent endosymbioses and HGT. One of these genes is an electron transfer protein (plastocyanin) of green algal origin in K. brevis that likely allows this species to thrive under conditions of iron depletion.     

Diversity and geographic distribution of secondary endosymbiotic bacteria in natural populations of the pea aphid,Acyrthosiphon pisum

In addition to the essential intracellular symbiotic bacterium Buchnera, several facultative endosymbiotic bacteria called collectively secondary symbionts (S-symbionts) have been identified from the pea aphid Acyrthosiphon pisum. We conducted an extensive and systematic survey of S-symbionts in Japanese local populations of A. pisum using a specific PCR detection technique. Five S-symbionts of A. pisum, PASS, PAUS, PABS, Rickettsia and Spiroplasma, and two facultative endosymbionts universally found in various insects, Wolbachia and Arsenophonus, were targeted. Of 119 isofemale strains originating from 81 localities, 66.4% of the strains possessed either of four S-symbionts: PASS (38.7%); PAUS (16.0%); Rickettsia (8.4%); and Spiroplasma (3.4%), while 33.6% of the strains contained only Buchnera. PABS, Wolbachia and Arsenophonus were not detected from the Japanese strains of A. pisum. In order to understand intra- and interpopulational diversity of S-symbiont microbiota in detail, 858 insects collected from 43 localities were examined for infection with the four S-symbionts. It was demonstrated that different S-symbionts coexist commonly in the same local populations, but double infections with two S-symbionts were rarely detected. Notably, the S-symbionts exhibited characteristic geographical distribution patterns: PASS at high frequencies all over Japan; PAUS at high frequencies mainly in the northeastern part of Japan; and Rickettsia and Spiroplasma at low frequencies sporadically in the southwestern part of Japan. These results indicate that the geographical distribution and infection frequency of the S-symbionts, in particular PAUS, might be affected by environmental and/or historical factors. Statistical analyses suggested that the distribution of PAUS infection might be related to host plant species, temperature and precipitation.     

COMPARATIVE ELECTROPHORETIC ANALYSIS OF TWO BINLJCLEATE DINOFLAGELLATES1

Although two clonal isolates of two different binucleate dinoflagellates Peridinium balticum (Levander) Letnmermann and Glcnodinium foliaceum Stein share a number of unique biochemical and ultrastructural attributes, comparative analysis for sixteen isozyme systems shows that these isolates are quite distinct from each other. Of the 129 different isozyme bands observed, only 28 were common to both organisms. These results support the contention based on plate tabulations that these two isolates should be placed in different genera and suggest that despite certain general biochemical and ultrastructural similarities that the isolates differ significantly at the biochemical and genetic levels and perhaps exhibit different adaptations between host and endosymbiont.     

Genome-Wide Survey and Evolutionary Analysis of Trypsin Proteases in Apicomplexan Parasites

Apicomplexa are an extremely diverse group of unicellular organisms that infect humans and other animals.Despite the great advances in combating infectious diseases over the past century,these parasites still have a tremendous social and economic burden on human societies,particularly in tropical and subtropical regions of the world.Proteases from apicomplexa have been characterized at the molecular and cellular levels,and central roles have been proposed for proteases in diverse processes.In this work,16 new genes encoding for trypsin proteases are identified in 8 apicomplexan genomes by a genome-wide survey.Phylogenetic analysis suggests that these genes were gained through both intracellular gene transfer and vertical gene transfer.Identification,characterization and understanding of the evolutionary origin of protease-mediated processes are crucial to increase the knowledge and improve the strategies for the development of novel chemotherapeutic agents and vaccines.     

茶小绿叶蝉成虫唾液细菌蛋白的鉴定

[目的]通过鉴定茶小绿叶蝉Empoasca flavescens成虫水状唾液蛋白中的细菌蛋白,解析叶蝉唾液的细菌种类.[方法]利用自制的收集装置和Parafilm膜夹营养液法对叶蝉成虫唾液进行收集,经超滤浓缩和电泳分离后,使用膜辅助样品制备技术法(filter-aided sample preparation,FASP...     

Role of soil microorganisms in improving P nutrition of plants

Phosphorus (P) is one of the major plant growth-limiting nutrients although it is abundant in soils in both inorganic and organic forms. Phosphate solubilizing micro-organisms (PSMs) are ubiquitous in soils and could play an important role in supplying P to plants in a more environmentally friendly and sustainable manner. Although solubilization of P compounds by microbes is very common under laboratory conditions, results in the field have been highly variable. This variability has hampered the large-scale use of PSMs in agriculture. Many reasons have been suggested for this variability, but none of them have been extensively investigated. In spite of the importance of PSMs in agriculture, the detailed biochemical and molecular mechanisms of P solubilization are not known. Recent work in our laboratory has shown that the conditions employed to isolate PSMs do not reflect soil conditions and that PSMs capable of effectively releasing P from soil are not so highly abundant as was suggested in earlier studies. These studies have also indicated that the mineral phosphate solubilizing (mps) ability of microbes could be linked to specific genes, and that these genes are present even in non P solubilizing bacteria. Understanding the genetic basis of P solubilization could help in transforming more rhizosphere-competent bacteria into PSMs. Further research should also focus on the microbial solubilization of iron (Fe) and aluminum (Al) phosphates, as well as mobilization of the organic phosphate reserves present in the soils.     

Non-linear bioconvection in a deep suspension of gyrotactic swimming micro-organisms

 The non-linear structure of deep, stochastic, gyrotactic bioconvection is explored. A linear analysis is reviewed and a weakly non-linear analysis justifies its application by revealing the supercritical nature of the bifurcation. An asymptotic expansion is used to derive systems of partial differential equations for long plume structures which vary slowly with depth. Steady state and travelling wave solutions are found for the first order system of partial differential equations and the second order system is manipulated to calculate the speed of vertically travelling pulses. Implications of the results and possibilities of experimental validation are discussed. Received: 26 May 1997 / Revised version: 10 May 1998     

The major carotenoid pigments of the grain aphid, Sitobion avenae (F.) (Hemiptera: Aphididae)

The economically important grain aphid, Sitobion avenae (F.) shows colour polymorphism, with brown and green forms predominating. Colour is determined both genetically and in response to environmental factors, including nutrition. The biological significance of the colour polymorphism is unknown, although seasonal changes occur in the frequency of colour morphs in the field, whilst the brown morph may have adaptive significance in terms of hymenopterous endoparasitism. The ground colour of aphids is produced by haemolymph pigments, aphins (glucosides) and carotenoids. The latter may be under the synthetic control of intracellular endosymbiotic bacteria. In this study, the major carotenoid pigments of a brown and a green clone of S. avenae were examined using thin layer chromatography (TLC) and high-performance liquid chromatography (HPLC), and their absorbance spectra recorded. Using TLC, the brown clone produced five bands of different R_f, ranging from yellow, to orange-pink to pink in colour. In contrast, the green clone gave only a single yellow band of higher R_f than any of the bands of brown aphids. Following separation of carotenoids by HPLC, brown aphids gave seven peaks and green aphids five. Comparison of absorbance maxima with known published values for carotenoids provides strong evidence for the identification of four of the carotenoid pigments from brown aphids (RB-4, 3,4-didehydrolycopene; RB-5, torulene; RB-6; lycopene; RB-7, γ-carotene) and one from green aphids (RG-2, α-carotene). The other carotenoids remain unidentified. The biosynthesis and possible biological relevance of the various pigments of S. avenae are briefly discussed.     

The V-type ATPase enhances photosynthesis in marine phytoplankton and further links phagocytosis to symbiogenesis

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