The Immense Diversity of Floral Monosymmetry and Asymmetry Across Angiosperms

Floral monosymmetry and asymmetry are traced through the angiosperm orders and families. Both are diverse and widespread in angiosperms. The systematic distribution of the different forms of monosymmetry and asymmetry indicates that both evolved numerous times. Elaborate forms occur in highly synorganized flowers. Less elaborate forms occur by curvature of organs and by simplicity with minimal organ numbers. Elaborate forms of asymmetry evolved from elaborate monosymmetry. Less elaborate form come about by curvature or torsion of organs, by imbricate aestivation of perianth organs, or also by simplicity. Floral monosymmetry appears to be a key innovation in some groups (e.g., Orchidaceae, Fabaceae, Lamiales), but not in others. Floral asymmetry appears as a key innovation in Phaseoleae (Fabaceae). Simple patterns of monosymmetry appear easily “reverted” to polysymmetry, whereas elaborate monosymmetry is difficult to lose without disruption of floral function (e.g., Orchidaceae). Monosymmetry and asymmetry can be expressed at different stages of floral (and fruit) development and may be transient in some taxa. The two symmetries are most common in bee-pollinated flowers, and appear to be especially prone to develop in some specialized biological situations: monosymmetry, e.g., with buzz-pollinated flowers or with oil flowers, and asymmetry also with buzz-pollinated flowers, both based on the particular collection mechanisms by the pollinating bees. Floral monosymmetry has developed into a model trait in evo-devo studies, whereas floral asymmetry to date has not been tackled in molecular genetic studies.     

Sensing trehalose biosynthesis in plants

A most unexpected finding in research on plant carbohydrate metabolism is the recent discovery that angiosperms encode genes whose products are involved in trehalose metabolism. The presence and functionality of such genes has been elegantly shown by expressing Arabidopsis-derived trehalose phosphate synthase and trehalose phosphate phosphatase genes in yeast mutants lacking these enzymatic activities. Homologue sequences have now been cloned from a number of different plant species suggesting that the capacity to synthesise trehalose is ubiquitous in angiosperms. Except for Myrothamnus flabellifolius, trehalose biosynthesis has never been observed in tissues of higher plants, probably due to the presence of high levels of trehalase activity. The function of trehalose metabolism in plants is still a mystery. One of the postulated functions of trehalose metabolism in yeast is in the control of glucose repression and a similar function in sugar sensing can be proposed for plants as well.     

An integrative insight on dormancy alleviation in diaspores of Urochloa humidicola (Rendle) Morrone & Zuloaga,a tropical grass with great economic and ecological impact

• Even though exhaustively studied, dormancy alleviation in diaspores of Urochloa humidicola (Rendle) Morrone & Zuloaga remains a mystery. To clarify this, we asked the following question: could dormancy alleviation in diaspores of this species be associated with ageing, GA/ABA balance and remaining structures of the panicoid spikelet?
• We answer this question using diaspores of U. humidicola cv. BRS Tupi as a biological model, a cultivar with a wide edaphoclimatic range in Neotropical areas and whose diaspores possess ‘deep dormancy’ when dispersed. We analysed both germination and early plant development using a split‐plot model.
• Our findings demonstrate that dormancy alleviation in diaspores of U. humidicola is a synergic phenomenon driven by crosstalk between age, GA/ABA balance and remaining structures of the panicoid spikelet covering caryopses, since this interaction acts on the dynamics of germination and early plant development.
• We demonstrate that: (i) spreading germination time is a maternal survival mechanism of this species, which has repercussions for occupational aggressiveness of the species; (ii) remaining structures of the panicoid spikelet covering caryopses are the main modulator of embryo development. These structures control the after‐ripening process, which is modulated by some molecular factor. We also highlight that it is necessary to review concepts about dormancy of dispersal units in this grass species.

     

An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG IV

Advances in recent years have revolutionized our understanding of both the context and occurrence of polyploidy in plants. Molecular phylogenetics has vastly improved our understanding of plant relationships, enabling us to better understand trait and character evolution, including chromosome number changes. This, in turn, has allowed us to appreciate better the frequent occurrence and extent of polyploidy throughout the history of angiosperms, despite the occurrence of low chromosome numbers in some groups, such as in Arabidopsis (A. thaliana was the first plant genome to be sequenced and assembled). In tandem with an enhanced appreciation of phylogenetic relationships, the accumulation of genomic data has led to the conclusion that all angiosperms are palaeopolyploids, together with better estimates of the frequency and type of polyploidy in different angiosperm lineages. The focus therefore becomes when a lineage last underwent polyploidization, rather than simply whether a plant is ‘diploid’ or ‘polyploid’. This legacy of past polyploidization in plants is masked by large‐scale genome reorganization involving repetitive DNA loss, chromosome rearrangements (including fusions and fissions) and complex patterns of gene loss, a set of processes that are collectively termed ‘diploidization’. We argue here that it is the diploidization process that is responsible for the ‘lag phase’ between polyploidization events and lineage diversification. If so, diploidization is important in determining chromosome structure and gene content, and has therefore made a significant contribution to the evolutionary success of flowering plants. © 2015 The Authors. Botanical Journal of the Linnean Society published by John Wiley & Sons Ltd on behalf of Linnean Society of London, 2016, 180 , 1–5.     

Evolutionary conservation of angiosperm flower development at the molecular and genetic levels

Flowers consist primarily of four basic organ types whose relative positions are universally conserved within the angiosperms. A model has been proposed to explain how a small number of regulatory genes, acting alone and in combination, specify floral organ identity. This model, known widely as the ABC model of flower development, is based on molecular generic experiments in two model organisms,Arabidopsis thaliana and Antirrhinum majus.Both of these species are considered to be eudicots, a clade within the angiosperms with a relatively conserved floral architecture. In this review, the application of the ABC model derived from studies of these typical eudicot species is considered with respect to angiosperms whose floral structure deviates from that of the eudicots. It is concluded that the model is universally applicable to the angiosperms as a whole, and the enormous diversity seen among angiosperms flowers is due to genetic pathways that are downstream, or independent, of the genetic programme that specifies floral organ identity.     

The genetic basis of a mutation that alters the floral symmetry in sunflower

The indeterminate inflorescence of sunflower (Helianthus annuus) is heterogamous with zygomorphic ray flowers in the outer whorl of the head and actinomorphic disc flowers arrayed in arcs radiating from the centre of the head. The Chrysanthemoides (Chry) mutant is characterised by a change of the radially symmetric corolla of tubular disc flowers into a monosymmetric ligulate‐like corolla. Zygomorphy is pronounced in the disc flowers placed on the peripheral whorls of inflorescences, while the monosymmetry is less marked toward the centre of the inflorescence. Although the Chry phenotype was one of first known morphological mutants in plants, studies on the genetic control of this trait are scarce and contradictory. Our results indicate that the Chry mutation is semidominant and exclude a maternal influence. Moreover, the data gathered in F₂, BC₁ and F₃ progenies support a genetic model involving one major locus and an unknown number of modifiers. The improved knowledge on genetic control of the Chry mutation should enhance the introduction of this trait in crossbreeding programmes designed to produce new varieties of ornamental sunflower.     

The good,the bad,and the ugly: which Australian terrestrial mammal species attract most research?

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Genomic dissection of pod shattering in common bean: mutations at non‐orthologous loci at the basis of convergent phenotypic evolution under domestication of leguminous species

The complete or partial loss of shattering ability occurred independently during the domestication of several crops. Therefore, the study of this trait can provide an understanding of the link between phenotypic and molecular convergent evolution. The genetic dissection of ‘pod shattering’ in Phaseolus vulgaris is achieved here using a population of introgression lines and next‐generation sequencing techniques. The ‘occurrence’ of the indehiscent phenotype (indehiscent versus dehiscent) depends on a major locus on chromosome 5. Furthermore, at least two additional genes are associated with the ‘level’ of shattering (number of shattering pods per plant: low versus high) and the ‘mode’ of shattering (non‐twisting versus twisting pods), with all of these loci contributing to the phenotype by epistatic interactions. Comparative mapping indicates that the major gene identified on common bean chromosome 5 corresponds to one of the four quantitative trait loci for pod shattering in Vigna unguiculata. None of the loci identified comprised genes that are homologs of the known shattering genes in Glycine max. Therefore, although convergent domestication can be determined by mutations at orthologous loci, this was only partially true for P. vulgaris and V. unguiculata, which are two phylogenetically closely related crop species, and this was not the case for the more distant P. vulgaris and G. max. Conversely, comparative mapping suggests that the convergent evolution of the indehiscent phenotype arose through mutations in different genes from the same underlying gene networks that are involved in secondary cell‐wall biosynthesis and lignin deposition patterning at the pod level.     

Phytochemistry of the Carnivorous Sundew Genus Drosera (Droseraceae) – Future Perspectives and Ethnopharmacological Relevance

Species of the carnivorous genus Drosera L. have long been a source of valuable natural products. The various phytochemicals characteristic of these species, particularly 1,4‐naphthoquinones and flavonoids, have contributed to the diverse utilization of sundews in traditional medicine systems worldwide. A growing number of studies have sought to investigate the comparative phytochemistry of Drosera species for improved sources of pharmaceutically important compounds. The outcomes of these studies are here collated, with emergent trends discussed in detail. Important factors which affect production of secondary metabolites in plants are critically examined, such as environmental influences and in vitro culture, and recommendations subsequently presented based on this. Explicitly, the current review aims to i) present an updated, comprehensive listing of the phytochemical constituents of the genus (including quantitative data where available), ii) summarize important factors which may influence the production of phytopharmaceuticals in plants, and iii) recommend guidelines for future research based on the above, including improved standardization and quality control. We have also included a section discussing future perspectives of research on Drosera spp. based on three different research lines i) the potential to produce much needed lead compounds for treatment of tuberculosis, ii) the potential role of anthocyanins in nitrogen transport, and iii) research into ‘Natural Deep Eutectic’ solvents produced by Drosera spp. in the droplets or ‘dew’ employed to capture insect prey.     

Computational identification of genes modulating stem height–diameter allometry

The developmental variation in stem height with respect to stem diameter is related to a broad range of ecological and evolutionary phenomena in trees, but the underlying genetic basis of this variation remains elusive. We implement a dynamic statistical model, functional mapping, to formulate a general procedure for the computational identification of quantitative trait loci (QTLs) that control stem height–diameter allometry during development. Functional mapping integrates the biological principles underlying trait formation and development into the association analysis of DNA genotype and endpoint phenotype, thus providing an incentive for understanding the mechanistic interplay between genes and development. Built on the basic tenet of functional mapping, we explore two core ecological scenarios of how stem height and stem diameter covary in response to environmental stimuli: (i) trees pioneer sunlit space by allocating more growth to stem height than diameter and (ii) trees maintain their competitive advantage through an inverse pattern. The model is equipped to characterize ‘pioneering’ QTLs (piQTLs) and ‘maintaining’ QTLs (miQTLs) which modulate these two ecological scenarios, respectively. In a practical application to a mapping population of full‐sib hybrids derived from two Populus species, the model has well proven its versatility by identifying several piQTLs that promote height growth at a cost of diameter growth and several miQTLs that benefit radial growth at a cost of height growth. Judicious application of functional mapping may lead to improved strategies for studying the genetic control of the formation mechanisms underlying trade‐offs among quantities of assimilates allocated to different growth parts.     

花器官发育的分子机制研究进展

经典的ABC模型成功地解释了模式植物拟南芥和金鱼草因同源异型基因突变而引起的植物花器官的变异。随后,大量花器官特征基因和新突变体的研究不断完善和发展了ABC模型。该文综述了近年来花器官发育分子模型及花器官同源基因的调控机理等方面的最新研究成果,并对未来的研究方向进行了展望,以期为深入了解花发育的分子机理和遗传机制奠定基础。     

Increasing the number of molecular markers resolves the phylogenetic relationship of ‘Cepaea’ vindobonensis (Pfeiffer 1828) with Caucasotachea Boettger 1909 (Gastropoda: Pulmonata: Helicidae)

‘Cepaea’ vindobonensis has been shown to be closely related to Caucasotachea in recent molecular studies. The phylogenetic relationships within this clade and especially the phylogenetic position of ‘Cepaea’ vindobonensis were, however, not well resolved. Our phylogenetic analyses on the basis of an increased number of molecular genetic loci from the mitochondrial and nuclear genomes unambiguously demonstrate that ‘Cepaea’ vindobonensis represents the sister group of the Caucasotachea taxa, with C. leucoranea from the Caspian region of Azerbaijan and Iran being the sister species of the remaining Caucasian and eastern Pontic Caucasotachea species. We argue for the inclusion of ‘Cepaea’ vindobonensis in Caucasotachea rather than for a re‐erection of a monotypic genus Austrotachea for the species because of the overall low degree of morphological differentiation and the low number of species in the group.     

Evidence for single gene resistance in apple to brownheaded leafroller, Ctenopseustis obliquana, and implications for resistance to other New Zealand leafrollers

The survival and development rate of Ctenopseustis obliquana (Walker) (Lepidoptera: Tortricidae) larvae, and weight of pupae were measured on detached mature leaves of two apple (Malus domestica Borkh.) progenies derived from the resistant (R) parent ‘Prima’ crossed with the susceptible (S) cultivars ‘Liberty’ (n = 44) and ‘Red Delicious’ (n = 35). The R:S ratio in both these modified backcross families did not differ significantly from the 1:1 expected in the case of monogenic resistance, carried in a heterozygous condition in the resistant parent. The survival to pupation on the individual seedlings was either zero/very low (R) or high (S). With all resistant seedlings being heterozygous, this indicates that the resistance allele shows complete dominance over the susceptible allele. We have named this putative gene Cob1. The expression of the resistance was found to be influenced by both the colony of C. obliquana used and the time of the season when resistance was assessed. In a separate experiment with another tortricid, there was no survival of Planotortrix octoDugdale larvae on the apple cultivar ‘Prima’ and high survival on the cultivars ‘Liberty’ and ‘Red Delicious’. The similarity of the responses of the two leafroller species to these cultivars, and other published evidence concerning Planotortrix excessana (Walker) and Ctenopseustis herana(Felder and Rogerhofer), suggest that the resistance discovered to C. obliquana may be effective against all four endemic tortricid species. The implications of these findings for apple breeding and leafroller control in New Zealand are discussed.     

A note on the ascorbic acid content of some trees and woody shrubs

The foliar ascorbic acid (vitamin C) content of 41 species of ‘woody’ shrubs and trees is recorded; the mean value for the 41 species was significantly greater (P < 0.0001) than that of ‘non-woody’ angiosperms previously examined.     

Molecular phylogeny and biogeography of African diploid barbs, ‘Barbus’, and allies in Africa and Asia (Teleostei: Cypriniformes)

African diploid barbs (‘Barbus’, Clypeobarbus, Barboides, etc.) are a group of small cyprinids with a body size less than 20 cm and widely distributed in drainages across Africa. These species constitute a significant component of African freshwater fish fauna. This study is the first to focus on the molecular systematics and biogeography of African diploid barbs ‘Barbus’ and its African and Asian allies using both mitochondrial and nuclear genes. We test for monophyly of groups, determine interspecific relationships and estimate the time of divergence of 52 species of ‘Barbus’ and allies using two mitochondrial and four nuclear genes. Resulting trees demonstrate that ‘Barbus’ and allies (Systomus, Barboides, Clypeobarbus and African tetraploid barbs) form a strongly supported clade; however, ‘Barbus’ is not resolved as monophyletic. Divergence time analyses identify the separation between Systomus and ‘Barbus’ plus African allies may have occurred around 26 MYA. In addition to the phylogenetic results, these findings highlight the need for more thorough taxonomic and systematic studies on ‘Barbus’ and allies using morphological and additional molecular data and greater taxon sampling, including the type species of the genus Enteromius, ‘Barbus’ potamogalis.     

Birding and DNA: species for the new millennium

Capsule Based on the 1999 Witherby Memorial Lecture – reviews how developments in molecular and population genetics have led to a reappraisal of species limits in birds.

The taxonomy of birds of the West Palearctic has moved from the comparative stability of the ‘Voous List’ into a period of serious activity, with new data emerging in almost every issue of every evolutionary and avian journal! This activity comes from two directions. Firstly, developments in population genetics, molecular biology, acoustics, behaviour and distributional studies have opened new avenues to measuring differentiation among groups of birds. This, in turn, has led to the recognition that earlier views of what constitutes a ‘species’ are in need of modification (‘improvement’), and the emergence of the ‘lineage concept’ of species. I review some of the species concepts most relevant to avian studies, and attempt to show how and why this change has happened, and its consequences for taxonomy and species limits. Examples are given in the form of ‘case studies’, and include Carrion/Hooded Crows Corvus corone/cornix, Green-winged/Eurasian Teals Anas carolinensis/crecca and Phylloscopus warblers.     

The relative contributions of refugium types to the persistence of benthic invertebrates in a seasonal snowmelt flood

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Electrostatic potentials of the S‐locus F‐box proteins contribute to the pollen S specificity in self‐incompatibility in Petunia hybrida

Self‐incompatibility (SI) is a self/non‐self discrimination system found widely in angiosperms and, in many species, is controlled by a single polymorphic S‐locus. In the Solanaceae, Rosaceae and Plantaginaceae, the S‐locus encodes a single S‐RNase and a cluster of S‐locus F‐box (SLF) proteins to control the pistil and pollen expression of SI, respectively. Previous studies have shown that their cytosolic interactions determine their recognition specificity, but the physical force between their interactions remains unclear. In this study, we show that the electrostatic potentials of SLF contribute to the pollen S specificity through a physical mechanism of ‘like charges repel and unlike charges attract’ between SLFs and S‐RNases in Petunia hybrida. Strikingly, the alteration of a single C‐terminal amino acid of SLF reversed its surface electrostatic potentials and subsequently the pollen S specificity. Collectively, our results reveal that the electrostatic potentials act as a major physical force between cytosolic SLFs and S‐RNases, providing a mechanistic insight into the self/non‐self discrimination between cytosolic proteins in angiosperms.