DNA barcoding the native flowering plants and conifers of Wales

We present the first national DNA barcode resource that covers the native flowering plants and conifers for the nation of Wales (1143 species). Using the plant DNA barcode markers rbcL and matK, we have assembled 97.7% coverage for rbcL, 90.2% for matK, and a dual-locus barcode for 89.7% of the native Welsh flora. We have sampled multiple individuals for each species, resulting in 3304 rbcL and 2419 matK sequences. The majority of our samples (85%) are from DNA extracted from herbarium specimens. Recoverability of DNA barcodes is lower using herbarium specimens, compared to freshly collected material, mostly due to lower amplification success, but this is balanced by the increased efficiency of sampling species that have already been collected, identified, and verified by taxonomic experts. The effectiveness of the DNA barcodes for identification (level of discrimination) is assessed using four approaches: the presence of a barcode gap (using pairwise and multiple alignments), formation of monophyletic groups using Neighbour-Joining trees, and sequence similarity in BLASTn searches. These approaches yield similar results, providing relative discrimination levels of 69.4 to 74.9% of all species and 98.6 to 99.8% of genera using both markers. Species discrimination can be further improved using spatially explicit sampling. Mean species discrimination using barcode gap analysis (with a multiple alignment) is 81.6% within 10×10 km squares and 93.3% for 2×2 km squares. Our database of DNA barcodes for Welsh native flowering plants and conifers represents the most complete coverage of any national flora, and offers a valuable platform for a wide range of applications that require accurate species identification.     

Genomics of Actinobacteria: tracing the evolutionary history of an ancient phylum.

Actinobacteria constitute one of the largest phyla among bacteria and represent gram-positive bacteria with a high G+C content in their DNA. This bacterial group includes microorganisms exhibiting a wide spectrum of morphologies, from coccoid to fragmenting hyphal forms, as well as possessing highly variable physiological and metabolic properties. Furthermore, Actinobacteria members have adopted different lifestyles, and can be pathogens (e.g., Corynebacterium, Mycobacterium, Nocardia, Tropheryma, and Propionibacterium), soil inhabitants (Streptomyces), plant commensals (Leifsonia), or gastrointestinal commensals (Bifidobacterium). The divergence of Actinobacteria from other bacteria is ancient, making it impossible to identify the phylogenetically closest bacterial group to Actinobacteria. Genome sequence analysis has revolutionized every aspect of bacterial biology by enhancing the understanding of the genetics, physiology, and evolutionary development of bacteria. Various actinobacterial genomes have been sequenced, revealing a wide genomic heterogeneity probably as a reflection of their biodiversity. This review provides an account of the recent explosion of actinobacterial genomics data and an attempt to place this in a biological and evolutionary context.     

Brassinosteroid action in flowering plants: a Darwinian perspective

The year 2012 marks the 150th anniversary of the publication of Charles Darwin's first botanical book, on the fertilization of orchids (1862), wherein he described pollen grains and outlined his evolutionary principles with respect to plant research. Five decades later, the growth-promoting effect of extracts of Orchid pollen on coleoptile elongation was documented. These studies led to the discovery of a new class of phytohormones, the brassinosteroids (BRs) that were isolated from rapeseed (Brassica napus) pollen. These growth-promoting steroids, which regulate height, fertility, and seed-filling in crop plants such as rice (Oryza sativa), also induce stress- and disease resistance in green algae and angiosperms. The origin and current status of BR-research is described here, with reference to BR-action and -signal transduction, and it is shown that modern high-yield rice varieties with erect leaves are deficient in endogenous BRs. Since brassinosteroids induce pathogen resistance in rice plants and hence can suppress rice blast- and bacterial blight-diseases, genetic manipulation of BR-biosynthesis or -perception may be a means to increase crop production. Basic research on BR activity in plants, such as Arabidopsis and rice, has the potential to increase crop yields further as part of a 21th century 'green biotech-revolution' that can be traced back to Darwin's classical breeding experiments. It is concluded that 'Nothing in brassinosteroid research makes sense except in the light of Darwinian evolution' and the value of basic science is highlighted, with reference to the genetic engineering of better food crops that may become resistant to a variety of plant diseases.     

Industrial production and utilization of enzymes from flowering plants

The papaya tree and barley are the only flowering plants now being utilized to any extent for commercial production of enzymes. The papaya fruit yields papain, a protein-digesting enzyme which can be used to eliminate or modify protein in several industries. Barley is germinated to malt, which contains amylase, necessary for the conversion of starchy materials to fermentable sugars. Malt is used to a great extent in the brewing and distilling industries. Other plants, for example, alfalfa, oranges and beans, are used to a minor extent in the preparation of enzymes for specific industrial purposes.     

Floral induction of vegetative plants supplied a purified fraction of deoxyribonucleic Acid from stems of flowering plants

It has been found that floral induced stems of flowering tobacco (Nicotiana tabacum cv. Wis. 38) plants contain large amounts of rapidly renaturing DNA, whereas noninduced stems of vegetative plants contain only small amounts. In addition, it has been shown that the striking qualitative difference in DNA between stems of flowering and vegetative plants mimics the over-all quantitative difference in DNA content (on a fresh weight basis). Therefore, the extra DNA in stems of flowering plants seems, at least in part, to represent preferential synthesis of rapidly renaturing DNA.     

Apomixis in flowering plants: an overview

Apomixis is a common feature of perennial plants, which occurs in ca. 60% of the British flora, but has been largely ignored by reproductive theoreticians. Successful individuals may cover huge areas, and live to great ages, favoured by 'symmetrical' selection. Apomixis is favoured by colonizing modes, for instance post-glacially. Despite its theoretical advantages, apomixis usually coexists with sexuality, suggesting 'hidden' disadvantages. Agamospermy (apomixis by seed) is relatively uncommon, but gains from the attributes of the seed. It pays agamospermy genes, which discourage recombination, to form co-adapted linkage groups, so that they become targets for disadvantageous recessive mutant accumulation. Consequently, agamospermy genes cannot succeed in diploids and agamosperms are hybrid and highly heterotic. Agamospermous endosperm may suffer from genomic imbalance, so that nutritious ovules, which can support embryos without endosperm, may be preadapted for agamospermy. When primary endosperm nucleus fertilization ('pseudogamy') continues as a requirement for many aposporous agamosperms, selfing sex becomes preadaptive and archesporial sex remains an option. Apomictic populations can be quite variable although apomictic families are much less variable than sexuals. Only in some diplosporous species does sex disappear completely, and in those species some release of variability may persist through somatic recombination. The search for an agamospermy gene suitable for genetic modification should target fertile sexuals with a single localized agamospermy (A) gene, which therefore lack a genetic load. The A gene should coexist alongside sexuality, so that it would be easy to select seedlings of sexual and asexual origins. Plants with sporophytic agamospermy provide all these attributes.     

Chromosome numbers of flowering plants from northern Norway and Svalbard

Chromosome numbers of 25 taxa of flowering plants from northern Norway and Svalbard are reported. Four species and one subspecies, Carex halophila F. Nyl. (2n = ca. 78), C. stenolepis Less. (2n = ca. 80), Salicorniapojarkovae N. Sem. (2n = 36), Alnus incano (L.) Moench ssp. kolaensis (Orlova) Love (2n = 28), and Saxifraga svalbardensis D. O. Øvstedal (2n = ca. 64), have not been studied karyologically before. Chromosome numbers of four additional species are reported for the first time from Norway; those of another six species for the first time from northern Norway. The hybrid Salix herbacea L. (2x) x 5. polaris Wahlenb. (6x) is proved tetraploid and may be fertile. A possible hybrid between Saxifraga hyperborea R. Br. and S. rivularis L. was revealed.     

Regeneration of flowering plants from difficile lily protoplasts by means of a nurse culture

The regeneration of difficile lily protoplasts isolated from suspension cells of the Oriental hybrid lily ( Lilium L.) cultivars Casablanca, Siberia and Acapulco was achieved by using the nurse-culture method. The divided protoplasts grew into colonies with nurse cells that have no regeneration ability, and developed to visible calli on a medium containing picloram. Many plantlets were formed on the calli after transfer of the proliferated calli to hormone-free medium. We were able to transplant the plantlets to soil in pots without acclimatization, and the plantlets grew in a greenhouse until flowering 2 years later.     

Haploids in flowering plants: origins and exploitation

The first haploid angiosperm, a dwarf form of cotton with half the normal chromosome complement, was discovered in 1920, and in the ninety years since then such plants have been identified in many other species. They can occur either spontaneously or can be induced by modified pollination methods in vivo, or by in vitro culture of immature male or female gametophytes. Haploids represent an immediate, one‐stage route to homozygous diploids and thence to F₁ hybrid production. The commercial exploitation of heterosis in such F₁ hybrids leads to the development of hybrid seed companies and subsequently to the GM revolution in agriculture. This review describes the range of techniques available for the isolation or induction of haploids and discusses their value in a range of areas, from fundamental research on mutant isolation and transformation, through to applied aspects of quantitative genetics and plant breeding. It will also focus on how molecular methods have been used recently to explore some of the underlying aspects of this fascinating developmental phenomenon.     

The alien flowering plants of Mexico

A list of 618 species of alien flowering plants recorded for Mexico is presented; they are distributed in 355 genera and 87 families. The families with the largest number of species are Poaceae (171), Fabaceae sensu lato (57), Asteraceae (56), and Brassicaceae (45). The representation of most families with alien species in Mexico agrees with the average distribution frequencies estimated by Pysek (1998 ) for 26 floras throughout the World. Exceptions are an under‐representation of Asteraceae and an over‐representation of Poaceae. Most alien species (78.9%) in Mexico have their origin in the Old World; South America ranks second with 9.6%. As defined by Richardson et al. (2000 ), 19.8% of the alien species could be considered casual aliens and 80.2% of them naturalized. The proportion of alien species relative to the 22,968 native flowering plant species recorded for Mexico is 2.7%.     

植物开花调控途径

开花是植物从营养生长转换为生殖生长的生理发育过程,受光周期、温度、激素、年龄等多个因素诱导,在植物生长和物种进化中处于核心地位。综合不断更新的开花分子遗传结果,将植物响应各种内源和外源信号启动开花的途径归纳为:经典的光周期途径、春化途径、自主途径、赤霉素途径和较新的年龄途径共5条。旨在描绘出这些不同途径间既独立又相互影响的复杂网络关系,为进一步探索和阐述更多植物的开花分子机理提供借鉴与参考。     

逆境诱导植物开花的研究进展

植物在长期的进化过程中形成了对环境改变的适应机制。在逆境条件下,例如干旱、高盐、低温、强光、弱光、紫外线等,植物会提前开花结实以尽早完成其生命周期,这种生物学现象被称为"逆境诱导的开花"。植物的这种避逆应激反应不但在进化上具有非常重要的生物学意义,而且对农业生产也具有重要的指导意义。逆境诱导植物开花与光周期、春化、环境温度、自主途径、赤霉素和年龄等开花途径的分子调控机制不同,有其自身的特点。文中对逆境诱导植物开花的研究历史、代谢调控以及分子机制等进行了阐述,并展望了未来的研究方向。     

Evolution of gametophytic apomixis in flowering plants: an alternative model from Maloid Rosaceae

Gametophytic apomixis, asexual reproduction involving megagametophytes, occurs in many flowering-plant families and as several variant mechanisms. Developmental destabilization of sexual reproduction as a result of hybridization and/or polyploidy appears to be a general trigger for its evolution, but the evidence is complicated by ploidy-level changes and hybridization occurring with facultative apomixis. The repeated origins of polyploid apomictic complexes in the palaeopolyploid Maloid Rosaceae suggest a new model of evolutionary transitions that may have wider applicability. Two conjectures are fundamental to this model: (1) that as previously suggested by Rutishauser, like many sexual flowering plants the polyploid apomicts require maternal–paternal balance in the second fertilization event that gives rise to the endosperm, and (2) that the observed variation in endosperm ploidy levels relates less to flexibility late in development than to the known variation in developmental origin of the megagametophyte between mechanisms loosely categorized as diplospory and apospory. The model suggests explanations for the relative frequencies of apospory and diplospory, and for the wide but incomplete associations of apospory with a pollination requirement (pseudogamy) and of diplospory with autonomous development of the endosperm. It is suggested that pollination from other taxa may provide some adaptive advantage to pseudogamous apospory. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.