基于matK基因和ITS序列探讨大叶藻科的系统发育关系

比较分析了15种大叶藻的matK基因和ITS片段的核苷酸序列, 结果发现胞嘧啶(C)在两个目的片段上含量均较低。ITS基因片段检测到228处核苷酸替换, 表现出丰富的遗传多态性; matK基因片段上有249处核苷酸替换, 且大部分替换来自于第三密码子的同义替换, 种间在氨基酸水平上产生了一定的分化。基于matK基因和ITS片段, 利用邻接法、最大简约法、最大似然法和贝叶斯法构建的系统发育树结果基本一致, 明显分为4大支, 大叶藻亚属、异叶藻属、拟大叶藻亚属和虾形藻属分别构成一支。大叶藻亚属和拟大叶藻亚属的核苷酸差异值在29.09%-35.51%, 超过了屈良鹄等提出的大部分被子植物ITS属间核苷酸差异值(9.60%-28.80%), 在分子数据上两亚属都达到了属的水平。研究结果支持Tomlinson和Posluszny对大叶藻科的划分结果, 建议将大叶藻科分为4个属。       

Chromosome numbers of the Australian Zosteraceae

 Somatic chromosome numbers of 2n = 24 are reported for all three species of Australian Zostera: Z. capricorni Aschers., Z. muelleri Irmisch ex Aschers. and Z. mucronata den Hartog and 2n = 36 for Heterozostera tasmanica (Martens ex Aschers.) den Hartog. All Australian zosteroidean species apparently have similar chromosome morphology: dot-like or rod shaped. It is suggested that the chromosome number and its morphology can be used to distinguish genera and subgenera in the Zosteraceae but not for species identification, and that speciation is not accompanied by changes of chromosome numbers. Received December 1, 1999 Accepted September 6, 2000     

Phylogenetic relationships in the genera<Emphasis Type="Italic"> Zostera</Emphasis> and<Emphasis Type="Italic"> Heterozostera</Emphasis> (Zosteraceae) based on<Emphasis Type="Italic"> matK</Emphasis> sequence data

Phylogenetic analysis of the plastid (chloroplast) DNA matK gene of Zosteraceae species was undertaken. A molecular phylogenetic tree based on matK sequence data showed the monophyly of Heterozostera tasmanica and subgenus Zosterella and did not support the separation of Heterozostera from the genus Zostera. The tree based on matK supported the monophyly of the subgenus Zostera, and showed that Zosteraceae consist of three main groups: Phyllospadix, which is clearly defined by being dioecious; the subgenus Zosterella and Heterozostera; and the subgenus Zostera. Character-state reconstruction of chromosome number and geographic distribution for our molecular phylogenetic tree showed that 2n=12 is a plesiomorphic character for Zostera and Heterozostera, that the chromosome number was doubled or tripled in two lineages, and that the initial speciation of Zostera and Heterozostera occurred in the Northern Hemisphere. The matK tree showed the close affinity of Z. noltii and Z. japonica, which have disjunct distributions. Zostera marina, which is the only widely distributed species in the subgenus Zostera, also occurring in the northern Atlantic, was shown to be embedded within other subgenus Zostera species.     

Evidence in favor of the symbiotic origin of chloroplasts: primary structure and evolution of tobacco glyceraldehyde-3-phosphate dehydrogenases

We report nucleotide sequences of cDNAs for the nuclear genes encoding chloroplast (GapA and GapB) and cytosolic (GapC) glyceraldehyde-3-phosphate dehydrogenases (GAPDH) from N. tabacum. Comparison of nucleotide sequences indicates that the GapA and GapB genes evolved following duplication of an ancestral gene about 450 million years ago. However, the divergence of GapA/B and GapC occurred much earlier in evolution than the divergence of GapC and GAPDH genes of animals and fungi, suggesting that chloroplast and cytosolic GAPDHs evolved from different lineages. Comparison of amino acid sequences shows that the chloroplast GAPDHs are related to GAPDHs found in thermophilic bacteria, while the cytosolic GAPDH is related to the GAPDH found in mesophilic prokaryotes. These results strongly support the symbiotic origin of chloroplasts.     

Molecular evolution of chloroplast DNA sequences

Comparative data on the evolution of chloroplast genes are reviewed. The chloroplast genome has maintained a similar structural organization over most plant taxa so far examined. Comparisons of nucleotide sequence divergence among chloroplast genes reveals marked similarity across the plant kingdom and beyond to the cyanobacteria (blue-green algae). Estimates of rates of nucleotide substitution indicate a synonymous rate of 1.1 x 10(-9) substitutions per site per year. Noncoding regions also appear to be constrained in their evolution, although addition/deletion events are common. There have also been evolutionary changes in the distribution of introns in chloroplast encoded genes. Relative to mammalian mitochondrial DNA, the chloroplast genome evolves at a conservative rate.      

大叶藻居群微卫星遗传多样性研究

采用4对微卫星引物对大叶藻的7个地理居群进行了遗传多样性与遗传结构分析。扩增148株大叶藻得到57个等位基因, 每个位点平均等位基因数为6, 大叶藻居群的平均期望杂合度(He)为0.687, 平均观测杂合度(Ho)为0.417。青岛湾居群的遗传多样性最高(A=7.750, AR=7.043), 俚岛居群最低(A=4.750, AR=4.543)。从F_st值来看, 7个大叶藻居群间属于中度分化。UPGMA系统发育树显示, 中国4个大叶藻居群聚类到一起, 其遗传分化可能是由于历史大海草场的遗留小片段居群产生, 而中国、韩国、日本和爱尔兰居群间的遗传分化则主要是由于地理隔离造成的。自由交配估计结果支持海草的东亚起源说。青岛湾居群遗传多样性较高, 可优先作为大叶藻移植修复的材料和基因库, 并进行重点保护。     

A comparison of rice chloroplast genomes

Using high quality sequence reads extracted from our whole genome shotgun repository, we assembled two chloroplast genome sequences from two rice (Oryza sativa) varieties, one from 93-11 (a typical indica variety) and the other from PA64S (an indica-like variety with maternal origin of japonica), which are both parental varieties of the super-hybrid rice, LYP9. Based on the patterns of high sequence coverage, we partitioned chloroplast sequence variations into two classes, intravarietal and intersubspecific polymorphisms. Intravarietal polymorphisms refer to variations within 93-11 or PA64S. Intersubspecific polymorphisms were identified by comparing the major genotypes of the two subspecies represented by 93-11 and PA64S, respectively. Some of the minor genotypes occurring as intravarietal polymorphisms in one variety existed as major genotypes in the other subspecific variety, thus giving rise to intersubspecific polymorphisms. In our study, we found that the intersubspecific variations of 93-11 (indica) and PA64S (japonica) chloroplast genomes consisted of 72 single nucleotide polymorphisms and 27 insertions or deletions. The intersubspecific polymorphism rates between 93-11 and PA64S were 0.05% for single nucleotide polymorphisms and 0.02% for insertions or deletions, nearly 8 and 10 times lower than their respective nuclear genomes. Based on the total number of nucleotide substitutions between the two chloroplast genomes, we dated the divergence of indica and japonica chloroplast genomes as occurring approximately 86,000 to 200,000 years ago.     

Straight-nosed pipefish Nerophis ophidion and broad-nosed pipefish Syngnathus typhle avoid eelgrass overgrown with filamentous algae

In a habitat choice experiment straight-nosed pipefish Nerophis ophidion and broad-nosed pipefish Syngnathus typhle avoided eelgrass Zostera marina covered with filamentous algae. Both juveniles as well as brooding adult males of the two species clearly preferred to position themselves in Z. marina without growth of filamentous algae.     

Eelgrass meadows in the California Channel Islands and adjacent coast reveal a mosaic of two species, evidence for introgression and variable clonality

BACKGROUND AND AIMS: Seagrasses are important facilitator species in shallow, soft-bottom marine environments worldwide and, in many places, are threatened by coastal development and eutrophication. One narrow-leaved species (Zostera marina) and one wide-leaved species, variously designated as Z. marina, Z. pacifica or Z. asiatica, are found off the California Channel Islands and adjacent California-Mexico coast. The aim of the present study was to confirm species identification genetically and to link patterns of genetic diversity, connectivity and hybridization among and within the populations with historical sea levels (Ice Age) or the contemporary environment. METHODS: Samples (n = 11-100) were collected from 28 sites off five California Channel Islands and six sites off the adjacent coast of southern California and Baja California, Mexico. DNA polymorphisms of the rDNA-ITS (internal transcribed spacer) cistron (nuclear), the matK intron (chloroplast) and nine microsatellite loci (nuclear) were examined in a population genetic and phylogeographic context. KEY RESULTS: All wide-leaved individuals were Z. pacifica, whereas narrow-leaved forms were Z. marina. Microsatellite genotypes were consistent with hybridization between the two species in three populations. The present distribution of Z. pacifica follows a glacial age land mass rather than present oceanographic regimes, but no link was observed between the present distribution of Z. marina and past or present environments. Island populations of Z. marina often were clonal and characterized by low genotypic diversity compared with populations along the Baja California coast. The high level of clonal connectivity around Santa Catalina Island indicated the importance of dispersal and subsequent re-establishment of vegetative fragments. CONCLUSIONS: The pristine environmental conditions of offshore islands do not guarantee maximum genetic diversity. Future restoration and transplantation efforts of seagrasses must recognize cryptic species and consider the degree of both genetic and genotypic variation in candidate donor populations.     

Phylogenetic analysis of North American Elymus and the monogenomic Triticeae (Poaceae) using three chloroplast DNA data sets.

Although the monogenomic genera of the Triticeae have been analyzed in numerous biosystematic studies, the allopolyploid genera have not been as extensively studied within a phylogenetic framework. We focus on North American species of Elymus, which, under the current genomic system of classification, are almost all allotetraploid, combining the St genome of Pseudoroegneria with the H genome of Hordeum. We analyze new and previously published chloroplast DNA data from Elymus and from most of the monogenomic genera of the Triticeae in an attempt to identify the maternal genome donor of Elymus. We also present a cpDNA phylogeny for the monogenomic genera that includes more data than, and thus builds on, those previously published. The chloroplast DNA data indicate that Pseudoroegneria is the maternal genome donor to all but one of the Elymus individuals. There is little divergence among the Elymus and Pseudoroegneria chloroplast genomes, and as a group, they show little divergence from the rest of the Triticeae. Within the monogenomic Triticeae, the problematic group Thinopyrum is resolved as monophyletic on the chloroplast DNA tree. At the intergeneric level, the data reveal several deeper-level relationships that were not resolved by previous cpDNA trees.     

Mechanism of Change in the Cation-Induced Excitation Energy Distribution Between PSⅡ and PS Ⅰ in the Chloroplast Membrane from Zostera marina

The interrelations between thylakoid polypeptide components and Mg2+-induced Chl a fluorescence and thylakoid surface charge changes were investigated in Zostera marina chloroplasts treated with Ca2+ and trypsin. It was observed that: 1. The increase of Mg2+- induced PS Ⅱ fluorescence intensity was closely related to the decrease of Mg2+-induced surface charge density of the thylakoid membrane in the normal chloroplast; 2. Removal of the 32～34 kD polypeptides of the thylakoid surface by Ca2+ extraction of the chloroplast did not affect the Mg2+-induced phenomena; 3. If the Ca2+-treated chloroplast was further digested by trypsin to remove the 26 kD polypeptide of the membrane surface, the Mg2+-induced phenomena disappeared completely. These results clearly indicated that the 26 kD polypeptide of thylakoid surface is the specific acting site of the cation that induced these two correlated phenomena in the chloroplast from Zostera marina. The mechanism on the regulating effect of the cation on excitation energy distribution between PS Ⅱ and PS Ⅰ was discussed.     

Seawater-resistant, non-spherical protoplasts from seagrass leaves

Two distinct types occurred among enzymatically isolated protoplasts from leaves of eelgrasses ( Zostera marina L., Z. japonica Ascherson and Phyllospadix iwatensis Makino). Spherical protoplasts with a smooth cell membrane were obtained only from young leaf tissues at the basal portions of blades protected from seawater by tightly enclosing sheaths. Non-spherical protoplasts had a highly invaginated cell membrane and were obtained from mature leaf blades, where the cells also in situ have this type of membrane. The protoplasts from mature leaves were rather rigid in shape and resistant to wide ranges of osmotic potential and salinity without change in their non-spherical shape, while the spherical protoplasts were rapidly destroyed in seawater. Detergents lysed the spherical protoplasts but not the non-spherical ones, suggesting that the highly invaginated enclosing structures of the non-spherical protoplasts contained detergent-resistant materials. Thus, the seagrass leaf cells develop seawater resistance, and this change alters the nature of the enclosing structures during the growth of the leaf blades. The non-membranous enclosing structures and their characteristic materials in the mature leaf cells remain to be defined.     

Molecular evolution and phylogeny of the atpB-rbcL spacer of chloroplast DNA in the true mosses.

The nucleotide variation of a noncoding region between the atpB and rbcL genes of the chloroplast genome was used to estimate the phylogeny of 11 species of true mosses (subclass Bryidae). The A+T rich (82.6%) spacer sequence is conserved with 48% of bases showing no variation between the ingroup and outgroup. Rooted at liverworts, Marchantia and Bazzania, the monophyly of true mosses was supported cladistically and statistically. A nonparametric Wilcoxon Signed-Ranks test Ts statistic for testing the taxonomic congruence showed no significant differences between gene trees and organism trees as well as between parsimony trees and neighbor-joining trees. The reconstructed phylogeny based on the atpB-rbcL spacer sequences indicated the validity of the division of acrocarpous and pleurocarpous mosses. The size of the chloroplast spacer in mosses fits into an evolutionary trend of increasing spacer length from liverworts through ferns to seed plants. According to the relative rate tests, the hypothesis of a molecular clock was supported in all species except for Thuidium, which evolved relatively fast. The evolutionary rate of the chloroplast DNA spacer in mosses was estimated to be (1.12 +/- 0.019) x 10(-10) nucleotides per site per year, which is close to the nonsynonymous substitution rates of the rbcL gene in the vascular plants. The constrained molecular evolution (total nucleotide substitutions, K approximately 0.0248) of the chloroplast DNA spacer is consistent with the slow evolution in morphological traits of mosses. Based on the calibrated evolutionary rate, the time of the divergence of true mosses was estimated to have been as early as 220 million years ago.     

Recent oceanic long-distance dispersal and divergence in the amphi-Atlantic rain forest genus Renealmia L.f. (Zingiberaceae)

Renealmia L.f. (Zingiberaceae) is one of the few tropical plant genera with numerous species in both Africa and South America but not in Asia. Based on phylogenetic analysis of nuclear ribosomal internal transcribed spacer (ITS) and chloroplast trnL-F DNA, Renealmia is shown to be monophyletic with high branch support. Low sequence divergence found in the two genome regions (ITS: 0-2.4%; trnL-F: 0-1.9%) suggests recent diversification within the genus. Molecular divergence age estimates give further support to the recent origin of the genus and show that Renealmia has attained its amphi-Atlantic distribution by an oceanic long-distance dispersal event from Africa to South America during the Miocene or Pliocene (15.8-2.7 My ago). Some support is found for the hypothesis that speciation in neotropical Renealmia was influenced by the Andean orogeny. Speciation has been approximately simultaneous on both sides of the Atlantic, but increased taxon sampling is required to compare the speciation rates between the New World and Old World tropics.     

Diffusivity in a marine macrophyte canopy: implications for submarine pollination and dispersal

The dispersion and capture of differently shaped particles within a Zostera marina L. (eelgrass; Zosteraceae) bed were examined to understand submarine pollination and other dispersals. During periods of moderate flow in the canopy, the capture rate of "spherical" (the shape of ancestral pollen) and "filamentous" (the shape of eelgrass pollen) particles was greater for particles released at the top of the canopy (3.07 and 4.53% × 10(-5) cm(-2) of collector; i.e., percentage of particles captured normalized to collector area) and greater for filamentous than for spherical particles (4.51% × 10(-5) cm(-2) vs. 2.01% × 10(-5) cm(-2)). Estimates of the horizontal P (Joseph-Sendner diffusion velocity) and the vertical diffusivity (Gaussian K) of filamentous particles were small (P ≈ 4 × 10(-4) m/s; K ≈ 10(-4) m(2)/s) compared to theoretical values that do not consider plant canopies. These findings support the concept that eelgrass canopies modify the fluid dynamics (i.e., reduced turbulent mixing) within their canopies. These results indicate that 1000-10?000 Z. marina pollen are required to pollinate a single flower. Similarly, it was estimated that under some conditions, the probability of particle impaction on eelgrass vegetation approaches certainty. These results provide insight into the evolution of filamentous pollen and submarine pollination, as well as dispersal and other mass transport phenomena within macrophyte canopies.     

Molecular evidence for a Mediterranean origin of the Macaronesian endemic genus Argyranthemum (Asteraceae)

The internal transcribed spacers (ITS) of nuclear ribosomal DNA were sequenced for 52 species from 32 genera and eight subtribes of Anthemideae. Phylogenetic analyses of ITS data generated trees that are largely incongruent with the recent classification of Anthemideae; most of the subtribes examined are not resolved as monophyletic. However, ITS trees are congruent with morphological, isozyme, phytochemical, and chloroplast DNA (cpDNA) restriction site data in supporting a Mediterranean origin for Argyranthemum, the largest endemic genus of the Atlantic oceanic islands. A combined analysis of ITS sequences and cpDNA restriction sites indicates that Argyranthemum is sister to the other three genera of Chrysantheminae (i.e., Chrysanthemum, Heteranthemis, and Ismelia). Times of divergence of Argyranthemum inferred from the ITS sequences ranged between 0.26 and 2.1 million years ago (mya) and are lower than values previously reported from isozyme and cpDNA data (1.5-3.0 mya). It is likely that rate heterogeneity of the ITS sequences in the Anthemideae accounts for the low divergence-time estimates. Comparison of data for 20 species in Argyranthemum and Chrysantheminae indicates that the cpDNA restriction site approach provided much more phylogenetic information than ITS sequences. Thus, restriction site analyses of the entire chloroplast genome remain a valuable approach for studying recently derived island plants.     

中国海草场的分布、生产力及其结构与功能的初步探讨

海草场是一类具有高度生产力的浅海生态系统(菊池泰山,1973)其主要的结构成分是海草。海草是只适应于海洋环境生活的维管束植物,属于沼生目(Helobiae),目前共发现有12属,其中9属是眼子菜科(Potamogetonaceac),3属归水鳖科(Hydrochartaceae)。分布在我国的有大叶藻(Zostera),虾形藻(Phyllospadix),二药藻(Halodule),海神草(Cymo-     

Salt-tolerant ATPase activity in the plasma membrane of the marine angiosperm Zostera marina L

Plasma membrane (PM) H(+)-ATPase and H(+) transport activity were detected in PM fractions prepared from Zostera marina (a seagrass), Vallisneria gigantea (a freshwater grass) and Oryza sativa (rice, a terrestrial plant). The properties of Z. marina PM H(+)-ATPase, specifically, the optimal pH for ATPase activity and the result of trypsin treatment, were similar to those of authentic PM H(+)-ATPases in higher plants. In V. gigantea and O. sativa PM fractions, vanadate-sensitive (P-type) ATPase activities were inhibited by the addition of NaCl. In contrast, activity in the Z. marina PM fraction was not inhibited. The nitrate-sensitive (V-type) and azide-sensitive (F-type) ATPase activities in the Z. marina crude microsomal fraction and the cytoplasmic phosphoenolpyruvate carboxylase activity, however, were inhibited by NaCl, indicating that not all enzyme activities in Z. marina are insensitive to salt. Although the ratio of Na(+) to K(+) (Na(+)/K(+)) in seawater is about 30, Na(+)/K(+) in the Z. marina cells was about 1.0. The salt-tolerant ATPase activity in the plasma membrane must play an important role in maintaining a low Na(+) concentration in the seagrass cells.     

Surface and submarine pollination in the seagrass Zoster a marina L

COX, P. A., LAUSHMAN, R. H. & RUCKLESHAUS, M. H., 1992. Surface and submarine pollination in the seagrass Zostera marina L. Hydrophilous plants can be divided into three ecological categories depending upon whether their pollen is transported above, on, or under the water surface. A mixed mode of submarine and surface hydrophilous pollination occurs in the seagrass Zostera marina L. In the surface mode of pollination, pollen rafts or 'search vehicles' which superficially resemble snowflakes, form at low tide and are transported on the surface of the sea by winds and water currents. Some of the search vehicles collide with the floating female stigmas, effecting pollination. In the submarine mode of pollination, small pollen masses resembling whisk brooms travel beneath the surface of the water. Although we failed to observe a submarine pollination event, SEM analysis of stigmas from subtidal populations confirms that submarine pollination does occur in Z. marina . However, observations of stigmas positioned at and below the surface of the water show surface pollination to be highly efficient. Electrophoretic evaluation of both subtidal and intertidal populations indicates significant genetic variation between populations. Given the high flux rates of surface-borne pollen and pollen viability in excess of 5 h, it is likely that surface-borne pollen is a major source of gene flow in Zostera marina populations.