Mode of pollen-tube growth in Pistils of Myrica rubra (Myricaceae): a comparison with related families

BACKGROUND AND AIMS: It is generally known that fertilization is delayed for more than a few weeks after pollination in Fagales. Recent studies showed that, during that period, pollen tubes grew in pistils in close association with the development of the ovule in a five-step process in Casuarina (Casuarinaceae) and a four-step process in Alnus (Betulaceae). The number of pollen tubes was reduced from many to one, a fact suggesting that delayed fertilization plays a role for gametophyte selection. Myrica (Myricaceae) also shows delayed fertilization for >2 weeks after pollination, but nothing is known of how pollen tubes grow in the pistil during that period. METHODS: Pollen-tube growth and the development of the ovule in pistils was investigated by fluorescent and scanning electron microscopy and analysis of microtome sections of the pistils. KEY RESULTS: Developmental study of the pollen-tube growth in the pistil of M. rubra showed that the tip of the pollen tube was branched or lay in a zigzag pattern in the upper space of the ovarian locule or near the tip of the integument, and subsequently was swollen on the nucellar surface. Such morphological changes indicate that the pollen-tube growth was temporarily arrested before fertilization. The pollen-tube growth in M. rubra can therefore be summarized as occurring in three steps: (1) from the stigma to the ovarian locule; (2) from the ovarian locule to the nucellar surface; and (3) from the nucellar surface to the embryo sac. CONCLUSION: Myrica differs from other families in that the pollen tubes arrest their growth on the nucellar surface, probably digesting nutrient from nucellar cells. There is little information on five other families of Fagales. An extensive study is needed to better understand the diversity and function of the mode of pollen-tube growth within the order.     

Changes in the chorion and sperm entry into the micropyle during fertilization in the teleostean fish, Oryzias latipes

Specific antibodies against the major chorionic glycoproteins (ZI1 -2 and ZI3) of unfertilized eggs were used to analyze the differences in the chorion and its surrounding constituents before and after fertilization. The glycoproteins in the inner layers of the chorion and its surrounding material were specifically stained by both of the antibodies. Thirty and 60 min after activation, the thickness of the chorion's inner layers was already reduced and the micropylar canal was closed. At the same time, the broadly diluted mucous area (DMA) of glycoproteins on the outermost layer of the chorion in unfertilized eggs was modified to a thin, compact layer. When unfertilized eggs were treated with trypsin, the inner third portion of the micropylar canal closed and the glycoproteins in the DMA were digested. The incidence of sperm entry into the micropyle of these eggs was extremely reduced. These results suggest that in medaka eggs, the chorionic glycoproteins in the DMA on the chorion surface, which have an affinity for spermatozo, play an important role in sperm guidance into the micropyle.     

Pollen-tube growth and fertilization mode in<Emphasis Type="Italic"> Gymnostoma</Emphasis> (Casuarinaceae): their characteristics and evolution

A unique mode of fertilization called chalazogamy, whereby the pollen tube passes through the chalaza instead of the micropyle, is known in several species of derived genera in Casuarinaceae. In this paper we report the occurrence of chalazogamy in Gymnostoma (G. poissonianum), the most primitive genus in the family. We also show that the pollen tube grows discontinuously from the stigma to ovules in about 3 months. At the time of pollination, the ovules have not yet formed in the ovary, and require a long time to develop. The pollen tube(s) lie in a zigzag line and are branched in the upper region of the style, and their growth is arrested there until the ovary develops further. Studies of the relevant literature further revealed discontinuous pollen-tube growth in relation to a prolonged period between pollination and fertilization, as well as chalazogamy, in Betulaceae, Juglandaceae and/or Fagaceae that are closely related to Casuarinaceae. This feature may have derived early in the evolution of Fagales.     

Chemical composition and anticancer activity of leaf essential oil of Myrica gale L.

Myrica gale L. (Myricaceae), a native plant from Canada used in traditional medicine, was extracted by hydrodistillation and the oil was collected after 30 and 60 min. The chemical composition of these two extracts was determined using GC-MS analysis. We identified 53 components and myrcene (23.18-12.14%), limonene (11.20-6.75%), alpha-phellandrene (9.90-6.49%) and beta-caryophyllene (9.31-10.97%) were the major components in the 30- and 60-min fractions, respectively, whereas higher caryophyllene oxide content was detected in the 60-min fraction (9.94%) than in the 30-min fraction (3.47%). The anticancer activities of these extracts were assessed against human lung carcinoma cell line A-549 and human colon adenocarcinoma cell line, DLD-1. The 60-min fraction showed higher anticancer activity against both tumor cell lines with an IC50 value of 88 +/- 1 microg/ml. The 30-min fraction had an IC50 value of 184 +/- 4 microg/ml for A-549 and 160 +/- 3 microg/ml for DLD-1. The higher cell growth inhibition induced by the 60-min fraction, as compared to the 30-min fraction, could be due to sesquiterpene enrichment.     

Winter nitrogen fertilization of loblolly pine seedlings

Loblolly pine (Pinus taeda L.) seedlings were nitrogen fertilized during winter in a bare root forest tree nursery located in the coastal plain of the southeastern United States. Total application rates were 0, 50, 100, and 200 kg/N/ha applied in split applications 4 weeks apart in January and February. Seedlings were lifted and outplanted in March, 4 weeks after the second fertilization and measured at 3 and 6 months after outplanting. No seedling morphological differences were encountered at the time of lifting and outplanting although seedling shoot nitrogen content was 28% greater in the highest fertilization treatment compared to the check. Shoot nitrogen concentrations fell after outplanting regardless of treatment, decreasing from an average of 1.51% across all treatments at the time of planting to 0.64% at 6 months after planting. When measured at 6 months after outplanting, seedling dry weight and height growth after planting was shown to increase by 12% and 24%, respectively, for the high nitrogen treatment. This and other studies across a variety of sites have found positive post-outplanting seedling growth response after nutrient loading in the nursery.     

The evolution of the Hox cluster: insights from outgroups

Two burgeoning research trends are helping to reconstruct the evolution of the Hox cluster with greater detail and clarity. First, Hox genes are being studied in a broader phylogenetic sampling of taxa: the past year has witnessed important new data from teleost fishes, onychophorans, myriapods, polychaetes, glossiphoniid leeches, ribbon worms, and sea anemones. Second, commonly accepted notions of animal relationships are being challenged by alternative phylogenetic hypotheses that are causing us to rethink the evolutionary relationships of important metazoan lineages, especially arthropods, annelids, nematodes, and platyhelminthes.     

Phylogeny of cardinalfishes (Teleostei: Gobiiformes: Apogonidae) and the evolution of visceral bioluminescence

The cardinalfishes (Apogonidae) are a diverse clade of small, mostly reef-dwelling fishes, for which a variety of morphological data have not yielded a consistent phylogeny. We use DNA sequence to hypothesize phylogenetic relationships within Apogonidae and among apogonids and other acanthomorph families, to examine patterns of evolution including the distribution of a visceral bioluminescence system. In conformance with previous studies, Apogonidae is placed in a clade with Pempheridae, Kurtidae, Leiognathidae, and Gobioidei. The apogonid genus Pseudamia is recovered outside the remainder of the family, not as sister to the superficially similar genus Gymnapogon. Species sampled from the Caribbean and Western Atlantic (Phaeoptyx, Astrapogon, and some Apogon species) form a clade, as do the larger-bodied Glossamia and Cheilodipterus. Incidence of visceral bioluminescence is found scattered throughout the phylogeny, independently for each group in which it is present. Examination of the fine structure of the visceral bioluminescence system through histology shows that light organs exhibit a range of morphologies, with some composed of complex masses of tubules (Siphamia, Pempheris, Parapriacanthus) and others lacking tubules but containing chambers formed by folds of the visceral epithelium (Acropoma, Archamia, Jaydia, and Rhabdamia). Light organs in Siphamia, Acropoma, Pempheris and Parapriacanthus are distinct from but connected to the gut; those in Archamia, Jaydia, and Rhabdamia are simply portions of the intestinal tract, and are little differentiated from the surrounding tissues. The presence or absence of symbiotic luminescent bacteria does not correlate with light organ structure; the tubular light organs of Siphamia and chambered tubes of Acropoma house bacteria, those in Pempheridae and the other Apogonidae do not.     

Competition between two grass species with and without grazing over a productivity gradient

Soil nutrient-level and herbivory are predicted to have opposing effects on the allocation pattern of the competitive dominant plant species. Lower stem and higher leaf allocation are favoured when plants are grazed, whereas a higher stem allocation is favoured at high nutrient levels. Grazing by hares and geese can prevent invasion of the tall Elymus athericus, into short vegetation of Festuca rubra, at unproductive stages of salt-marsh succession but not at more productive stages. We hypothesise that the negative effect of herbivory on Elymus decreases due to increasing soil nitrogen levels and shifts the competitive balance towards this species. We tested how simulated grazing and nitrogen availability affected the competitive balance between adult plants of both grass species in a greenhouse experiment. Elymus had a higher above-ground biomass production, invested relatively more in stem and root tissue and had a larger shoot length than Festuca. The above-ground relative yield of Elymus in mixtures of both species increased with increasing nitrogen levels. This indicates that Elymus was the superior competitor at high soil fertility. Although clipping removed relatively more biomass from Elymus than from Festuca and exceeded the observed biomass removal in field conditions, it did not change the competitive balance between both species. Decreasing effects of herbivory due to increasing nitrogen levels are not a likely explanation for the invasion of Elymus in productive marshes. The results suggest that once Elymus has established it can easily invade vegetation dominated by Festuca irrespective of grazing by herbivores such as hares and geese. Herbivory by small herbivores may mainly retard the invasion of this plant by influencing establishment itself.     

柠檬醛对杨梅采后保鲜的作用研究

杨梅(Myrica rubra Sieb.Zucc.)是一种富含抗氧化物的健康水果,但极易腐烂变质,应用生物保鲜剂对杨梅保鲜具有无毒、经济和易推广等优点。本研究从自然腐烂的杨梅中分离纯化出7种腐烂病原菌菌株,其中Penicillium georgiense首次在杨梅采后病腐中被报道;在此基础上研究了柠檬醛对杨梅采后保鲜效果和对4种主要杨梅腐烂病原菌的抑菌机理。结果表明:用1.00%(体积分数)柠檬醛对杨梅进行熏蒸处理,可显著提高冷贮条件下杨梅的好果率;柠檬醛抑菌动力学研究表明0.10%(体积分数)柠檬醛可有效抑制4种病原菌孢子形成,从而抑制病原菌生长繁殖,以降低杨梅腐烂率。柠檬醛是一种有效的杨梅抑菌保鲜剂,它的应用将有利于杨梅采后保鲜,并可促进这一果树资源的开发利用。     

Every sperm is sacred: fertilization in Caenorhabditis elegans

The nematode Caenorhabditis elegans is an attractive model system for the study of fertilization. C. elegans exists as a self-fertilizing hermaphrodite or as a male. This unusual situation provides an excellent opportunity to identify and maintain sterile mutants that affect sperm and no other cells. Analysis of these mutants can identify genes that encode proteins required for gamete recognition, adhesion, signaling, fusion, and/or activation at fertilization. These genes can also provide a starting point for the identification of additional molecules required for fertility. This review describes progress in the genetic and molecular dissection of fertilization in C. elegans and related studies on sperm competition.     

Mitochondrial phylogeny reveals differential modes of chromosomal evolution in the genus Tatera (Rodentia: Gerbillinae) in Africa

The African gerbils of the genus Tatera are widespread and abundant throughout sub-Saharan Africa. There is still today a certain controversy concerning the taxonomy of these rodents and very few attempts have been made to assess their systematic relationships. The present paper introduces findings based on the partial sequences of cytochrome b (495 bp) and the 16S rRNA (469 bp) mitochondrial genes of six (T. robusta, T. nigricauda, T. vicina, T. leucogaster, T. valida, and T. kempi) species together with two additional taxa. We also report the karyotypes of T. vicina and T. leucogaster. We propose that T. vicina should be considered as a valid species and show the monophyly of the robusta species group, with the exclusion of T. leucogaster. Our results show there is a different chromosomal evolutionary pattern within the two major lineages, which is recognizable through molecular phylogenetics. One is characterized by karyotype stability and the other by a considerable number of chromosomal rearrangements. The lineage divergence coincides with the formation of the East African Rift. The processes that led to the origin of the East African species seem to be related to the subsequent climatic changes, which caused cyclic contraction and expansion of the savannah biomes. Furthermore, geological activities that characterized East Africa during Plio-Pleistocene may also have contributed to lineage divergence.     

Microsatellite analysis of the maternal origin of <Emphasis Type="Italic">Myrica rubra</Emphasis> seeds in the feces of Japanese macaques

Identifying the maternal origin of dispersed seeds is a challenging task because it is impossible to directly track seed movement once an animal has ingested them. However, recent development of molecular techniques allows us to identify the maternal origin of dispersed seeds in natural plant populations. Here we analyzed the maternal origin of Myrica rubra seeds found in the feces of Yakushima macaques. We detected a high level of diversity among the dispersed seeds, with an average of 3.0 maternal origins (range 1–9) in each feces. The average dispersal distance was 270.0 m (range 20.4–634.0 m) and the average of distance between maternal trees of dispersed seeds in the same feces was 161.5 m (range 0–573.9 m). These results suggest that seed dispersal by macaques plays an important role in maintaining the genetic diversity of Myrica rubra populations.     

Double fertilization inEphedra trifurca,a non-flowering seed plant: The relationship between fertilization events and the cell cycle

Summary Fertilization inEphedra trifurca was examined with a combination of light and fluorescence microscopy. Developmental analysis clearly indicates that double fertilization events, similar to those described inE. nevadensis, regularly occur during the process of sexual reproduction inE. trifurca. In addition to the typical fusion of a sperm nucleus and egg nucleus, a second fertilization event occurs between the second sperm nucleus from an individual pollen tube and the ventral canal nucleus. Both of the fertilization events take place within the confines of an individual egg cell of the female gametophyte. Microspectrofluorometric data demonstrate that each nucleus involved in a sexual fusion event proceeds through the synthesis phase of the cell cycle and increases its DNA content from 1C to 2C before the process of nuclear fusion is completed. Photometric data also confirm that the product of the second fertilization event is equal in DNA content (4C) to the zygotic nucleus derived from the first fertilization event, and is prepared to enter into mitosis as a fully functional diploid nucleus.Abbreviations DAPI 4;,6-diamidino-2-phenylindole - RFU relative fluorescence units     

Reconstructing the evolution of agarics from nuclear gene sequences and basidiospore ultrastructure

Traditional classifications of agaric fungi involve gross morphology of their fruit bodies and meiospore print-colour. However, the phylogeny of these fungi and the evolution of their morphological and ecological traits are poorly understood. Phylogenetic analyses have already demonstrated that characters used in traditional classifications of basidiomycetes may be heavily affected by homoplasy, and that non-gilled taxa evolved within the agarics several times. By integrating molecular phylogenetic analyses including domains D1–D3 and D7–D8 of nucLSU rDNA and domains A–C of the RPB1 gene with morphological and chemical data from representative species of 88 genera, we were able to resolve higher groups of agarics. We found that the species with thick-walled and pigmented basidiospores constitute a derived group, and hypothesize that this specific combination of characters represents an evolutionary advantage by increasing the tolerance of the basidiospores to dehydration and solar radiation and so opened up new ecological niches, e.g. the colonization of dung substrates by enabling basidiospores to survive gut passages through herbivores. Our results confirm the validity of basidiospore morphology as a phylogenetic marker in the agarics.     

Phylogeny of the avian genus Pitohui and the evolution of toxicity in birds

Bird species in the avian genus Pitohui contain potent neurotoxic alkaloids that may be used for defense. The genus comprises multiple species that are endemic to New Guinea and were presumed to belong to the family Pachycephalidae or Colluricinclidae, within the core corvoidea, an ancient Australasian radiation of crow-like birds. In order to understand the evolution of toxicity within the genus Pitohui, we sequenced three mitochondrial and two nuclear gene segments and reconstructed a phylogeny of the genus Pitohui and its putative relatives. We show that the genus Pitohui is polyphyletic, and consists of five different lineages. Using Bayesian ancestral state reconstruction, we estimate that toxicity likely evolved multiple times within this group. Furthermore, because the morphological and behavioral similarity among these poisonous birds appears to have evolved convergently, we hypothesize that this may be a possible example of Müllerian mimicry in birds. The Morningbird of Palau, Micronesia, that has often been included in the genus Pitohui, actually belongs in the genus Pachycephala and offers an intriguing case of pronounced evolution on a remote oceanic island.     

走出青藏高原：拉格啤酒酵母的起源与演化

采用低温底层发酵的拉格(lager)啤酒15世纪开始在德国巴伐利亚地区出现,19世纪初流行至全世界,目前已成为全球产量最高的酒精饮料。目前已阐明,拉格啤酒发酵酵母为巴斯德酿酒酵母(Saccharomyces pastorianus),该种是一个杂交种,由艾尔(ale)啤酒酵母(Saccharomyces cerevisiae)与野生真贝氏酿酒酵母(Saccharomyces eubayanus)杂交而成,后者赋予了拉格啤酒酵母的耐低温能力。近年的群体遗传学和群体基因组学研究表明,拉格啤酒酵母的野生亲本S.eubayanus起源于青藏高原,可能通过丝绸之路传播到了欧洲。比较基因组学研究表明,拉格啤酒酵母包含2个株系,即Ⅰ系/Saaz系和Ⅱ系/Frohberg系,早期分别流行于中欧和西欧地区。前者为近似异源3倍体,后者为近似异源4倍体。2个株系在耐低温、麦芽三糖利用和风味物质产生能力等方面具有明显差异。在中国普通微生物菌种保藏管理中心(China General Microbiological Culture Collection Center,CGMCC)保藏的S.pastorianus...     

Mode of pollen tube growth in pistils of Ticodendron incognitum (Ticodendraceae,Fagales) and the evolution of chalazogamy

Ticodendron incognitum is the sole species of the Ticodendraceae, which was established as a new family in the Fagales less than 20 years ago. Considering the diverse modes of pollen tube growth observed in other Fagales, we investigated the growth of pollen tubes in the pistil of Ticodendron. At the time of pollination, T. incognitum had four immature ovules in a bilocular ovary, thus exhibiting delayed fertilization, as in other Fagales. During the period when fertilization was delayed, pollen tube growth in the pistil was intermittent, consisting of five steps associated with development of the ovules and embryo sacs. Four cessation sites occurred: in the style, in the tissue of the upper part of the ovary, inside and outside of the funicle and at the chalaza. A single pollen tube eventually reaches a mature embryo sac through the chalaza in one of the four ovules. While both delayed fertilization and intermittent pollen tube growth play a role in male and female gametophyte selection, as in other Fagales, the five‐step process of pollen tube growth through the chalaza (i.e. chalazogamy) is characteristic of lineages of the Casuarinaceae, Ticodendraceae and Betulaceae (the latter with the loss of one step). © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 157 , 621–631.     

Fourfold polyphyly of the genus formerly known as Upucerthia, with notes on the systematics and evolution of the avian subfamily Furnariinae

The traditional avian subfamily Furnariinae, a group of terrestrial ovenbirds typical of the Andean and Patagonian arid zones, consists of the genera Furnarius, Cinclodes, Geositta, Upucerthia, Chilia, and Eremobius. We investigated phylogenetic relationships within the Furnariinae, with particular attention to the nine species of the genus Upucerthia, using nuclear and mitochondrial DNA sequences from all genera in the subfamily. Upucerthia was found to be highly polyphyletic, its constituent species forming four non-sister clades: (1) a basal lineage consisting of two Upucerthia species, U. ruficaudus and U. andaecola, as well as the monotypic genera Eremobius and Chilia; (2) a lineage consisting of U. harterti and U. certhioides, two species behaviorally divergent from other Upucerthia species; (3) a lineage consisting of U. serrana, which is not closely related to any other Upucerthia species; and (4) a lineage, sister to Cinclodes, consisting of the four Upucerthia species U. dumetaria, U. albigula, U. validirostris, and U. jelskii. The larger Furnariinae was also found to be highly polyphyletic; the terrestrial open country ecotype characteristic of this subfamily occurs in four unrelated clades in the family Furnariidae, including a basal lineage as well as derived lineages. Although the large degree of divergence among Upucerthia clades was not previously recognized, owing to ecological, behavioral, and morphological similarities, the groupings correspond closely to relationships suggested by plumage. This is in contrast to studies of other avian genera in which plumage patterns have been shown to be extensively convergent. The generic names Upucerthia and Ochetorhynchus are available for two of the former Upucerthia clades; new generic names may be warranted for the other two.