Leitch A.R.,Queen Mary, University of London |
Leitch I.J.,Jodrell Laboratory
New Phytologist | Year: 2012
The large-scale replacement of gymnosperms by angiosperms in many ecological niches over time and the huge disparity in species numbers have led scientists to explore factors (e.g. polyploidy, developmental systems, floral evolution) that may have contributed to the astonishing rise of angiosperm diversity. Here, we explore genomic and ecological factors influencing seed plant genomes. This is timely given the recent surge in genomic data. We compare and contrast the genomic structure and evolution of angiosperms and gymnosperms and find that angiosperm genomes are more dynamic and diverse, particularly amongst the herbaceous species. Gymnosperms typically have reduced frequencies of a number of processes (e.g. polyploidy) that have shaped the genomes of other vascular plants and have alternative mechanisms to suppress genome dynamism (e.g. epigenetics and activity of transposable elements). Furthermore, the presence of several characters in angiosperms (e.g. herbaceous habit, short minimum generation time) has enabled them to exploit new niches and to be viable with small population sizes, where the power of genetic drift can outweigh that of selection. Together these processes have led to increased rates of genetic divergence and faster fixation times of variation in many angiosperms compared with gymnosperms. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.
Bennett M.D.,Jodrell Laboratory |
Leitch I.J.,Jodrell Laboratory
Annals of Botany | Year: 2011
Background and AimsThe amount of DNA in an unreplicated gametic chromosome complement is known as the C-value and is a key biodiversity character of fundamental significance with many practical and predictive uses. Since 1976, Bennett and colleagues have assembled eight compilations of angiosperm C-values for reference purposes and subsequently these have been pooled into the Angiosperm DNA C-values Database (http://data.kew.org/cvalues/). Since the last compilation was published in 2005, a large amount of data on angiosperm genome size has been published. It is therefore timely to bring these data together into a ninth compilation of DNA amounts.ScopeThe present work lists DNA C-values for 2221 species from 151 original sources (including first values for 1860 species not listed in previous compilations). Combining these data with those published previously shows that C-values are now available for 6287 angiosperm species.Key FindingsAnalysis of the dataset, which is by far the largest of the nine compilations published since 1976, shows that angiosperm C-values are now being generated at the highest rate since the first genome sizes were estimated in the 1950s. The compilation includes new record holders for the smallest (1C 0·0648 pg in Genlisea margaretae) and largest (1C 152·23 pg in Paris japonica) genome sizes so far reported, extending the range encountered in angiosperms to nearly 2400-fold. A review of progress in meeting targets set at the Plant Genome Size meetings shows that although representation for genera, geographical regions and some plant life forms (e.g. island floras and parasitic plants) has improved, progress to increase familial representation is still slow. In terms of technique it is now clear that flow cytometry is soon likely to become the only method available for plant genome size estimations. Fortunately, this has been accompanied by numerous careful studies to improve the quality of data generated using this technique (e.g. design of new buffers, increased awareness and understanding of problems caused by cytosolic inhibitors). It is also clear that although the speed of DNA sequencing continues to rise dramatically with the advent of next-generation and third-generation sequencing technologies, 'complete genome sequencing' projects are still unable to generate accurate plant genome size estimates. © The Author 2011. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved.
Prenner G.,Jodrell Laboratory
Annals of Botany | Year: 2013
Background and Aims The inflorescence structure determines the spatiotemporal arrangement of the flowers during anthesis and is therefore vital for reproductive success. The Leguminosae are among the largest angiosperm plant families and they include some important crop plants. In papilionoid legumes, the raceme is the most common type of inflorescence. However, a range of other inflorescence types have evolved via various developmental processes. A (re-)investigation of inflorescences in Swainsona formosa, Cicer arietinum, Abrus precatorius, Hardenbergia violacea and Kennedia nigricans leads to new insights into reduction mechanisms and to a new hypothesis on the evolution of the papilionoid pseudoraceme. Methods Inflorescence morphology and ontogeny were studied using scanning electron microscopy (SEM). Key Results The inflorescence in S. formosa is an umbel with a rare type of pendulum symmetry which may be triggered by the subtending leaf. Inflorescences in C. arietinum are reduced to a single flower. An early formed adaxial bulge is the sterile apex of the inflorescence (i.e. the inflorescence is open and not terminated by a flower). In partial inflorescences of A. precatorius, the axis is reduced and its meristem is relocated towards the main inflorescence. Flower initiation follows a peculiar pendulum pattern. Partial inflorescences in H. violacea and in K. nigricans show reduction tendencies. In both taxa, initiated but early reduced bracteoles are present. Conclusions Pendulum symmetry in S. formosa is probably associated with distichous phyllotaxis. In C. arietinum, strong reduction tendencies are revealed. Based on studies of A. precatorius, the papilionoid pseudoraceme is reinterpreted as a compound raceme with condensed lateral axes. From an Abrus-like inflorescence, other types can be derived via reduction of flower number and synchronization of flower development. A plea is made for uniform usage of inflorescence terminology.©The Author 2013. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved.
Rudall P.J.,Jodrell Laboratory
Current Opinion in Plant Biology | Year: 2010
Understanding floral patterning is a primary goal in plant biology, yet the temporal sequence of organ development is rarely factored into developmental models. In flowers, occasional examples of centrifugal or basipetal organ initiation, both within organ zones (intrazonal) and between them (interzonal), present a paradox with respect to developmental models. A centripetal/acropetal sequence of floral organ initiation is ancestral in angiosperms, but centrifugal/basipetal development has evolved many times, indicating that these apparently major developmental shifts have relatively simple genetic triggers. Review of the sequence of organ initiation in angiosperms supports evidence that the four floral organ types develop independently of each other, in response to genetic factors that predetermine radial patterning. © 2009 Elsevier Ltd. All rights reserved.
Veitch N.C.,Jodrell Laboratory
Natural Product Reports | Year: 2013
This account describes 275 new isoflavonoids published between 2008 and 2011 as constituents of the Leguminosae, commenting on their source, identification, biological activity, synthesis, and ecological or chemosystematic significance. Applications of hyphenated analytical techniques to the characterisation of Leguminosae isoflavonoids are also reviewed, together with advances in biosynthetic studies. A checklist of new compounds by species is given, and 226 references are cited. This journal is © The Royal Society of Chemistry.
Furness C.A.,Jodrell Laboratory
International Journal of Plant Sciences | Year: 2011
Malpighiales are one of the least resolved of the major angiosperm orders; more comparative data are needed to elucidate deep relationships and character evolution within the order. This article reevaluates pollen and tapetal characters, with a focus on one major subclade, the parietal clade. Pollen structure and, where possible, development are examined in representatives of the parietal clade from Passifloraceae (Passiflora, Turnera), Salicaceae (Populus, Salix), and Violaceae (Viola), and in Euphorbia (Euphorbiaceae), Hypericum (Hypericaceae), and Linum and Reinwardtia (Linaceae) from other Malpighiales. Pollen and tapetal characters in the parietal clade and selected outgroups are tabulated, using both original observations and an extensive literature search. Optimization of pollen and tapetal characters onto a recent molecular phylogeny indicates that lalongate endoapertures are a potential synapomorphy for the parietal clade. Passifloraceae (including the former Turneraceae) have some potential apomorphies: larger pollen size, greater diversity in endoaperture shape, and a plasmodial tapetum. The occurrence of a thick bilayered or channeled apertural intine may support a sister relationship between Passifloraceae and Violaceae, together with pollen with more than three colporate apertures. Very small pollen size indicates that Goupiaceae are potentially more closely related to the Lacistemataceae-Salicaceae clade than to Passifloraceae-Violaceae. Highly apomorphic, thin-walled, inaperturate pollen occurs in the wind-pollinated Populus. Outside the parietal clade, Malpighiales pollen is highly diverse, including large, intectate, baculate pollen in Linaceae with an exine composed of sporopollenin granules that could be an example of paedomorphosis, and unusual aperture structure in Euphorbia, with similarities to opercula. This pollen diversity may be a consequence of the considerable ecological diversity of Malpighiales and their rapid radiation in the mid-Cretaceous, and it indicates the need for further work on pollen and tapetal characters in this clade. © 2011 by The University of Chicago. All rights reserved.
Green P.W.C.,Jodrell Laboratory
Journal of Stored Products Research | Year: 2011
A methanol fraction (MFr), prepared from 80% methanol extracts of whole Liposcelis bostrychophila, repels conspecifics when presented to groups of insects at 8000 ppm. To examine the reason for this repellent effect, bioassays tested a mixture of fatty acids and fatty acid methyl esters that are present in the MFr at concentrations ranging from 0.02 to 1.2 mM. This mixture of compounds contributes significantly to the repellence of the MFr. Therefore, an interaction among compounds can affect the settling behaviour of L. bostrychophila, even though the individual compounds do not have any effect. Other experiments further investigated the repellence of C16 and C18 fatty acids. In the majority of instances groups of insects consistently settled on the disc impregnated with either stearic acid or the compound with the most saturated bonds. The one exception was C18:2 versus C18:3 where more insects settled on C18:3. This repellent effect of unsaturated fatty acids was also evident in five-way choice tests using a series of C18 fatty acids, where stearic acid (10 mM) was consistently selected by groups of L. bostrychophila instead of oleic, linoleic and linolenic acid. The discrimination between and among fatty acids could be due to the differences in their physical properties which affect how the compounds are perceived by the insects. The fact that the most unsaturated fatty acids repel the insects presents the possibility that volatile insect-derived compounds could be utilised as repellents for this increasingly important pest. © 2011 Elsevier Ltd.
Veitch N.C.,Jodrell Laboratory |
Grayer R.J.,Jodrell Laboratory
Natural Product Reports | Year: 2011
This review describes 796 new examples of naturally occurring flavonoids found either as aglycones or glycosides, comprising flavones, flavonols, chalcones, dihydrochalcones, aurones, flavanones, dihydroflavonols, and anthocyanins. The main topics addressed are source, identification, biological activity, biosynthesis, synthesis, and ecological or chemosystematic significance, and 562 references are cited. © 2011 The Royal Society of Chemistry.
Prenner G.,Jodrell Laboratory
South African Journal of Botany | Year: 2013
The jequirity bean (Abrus precatorius) is well known because of its shiny black and red coloured seeds and because of the poison (abrin) it contains. The genus Abrus is placed in a monogeneric tribe Abreae which is placed in a relatively isolated systematic position at the base of Millettieae. To contribute to a better understanding of this taxon, a detailed ontogenetic and morphologic analysis of its flowers is presented. Floral primordia are subtended by an abaxial bract and preceded by two lateral bracteoles which are formed in short succession. Sepal formation is unidirectional starting abaxially. All petals are formed simultaneously. The carpel is formed concomitantly with the outer (antesepalous) stamen whorl, which arises unidirectionally, starting in an abaxial position. In the inner, antepetalous stamen whorl two abaxial stamens are formed first, followed by two lateral stamen primordia. The adaxial, antepetalous position remains organ free (i.e. this stamen is lost). Later in development the nine stamen filaments fuse to form an adaxially open sheath. The filament bases of the two adaxial outer-whorl stamens grow inwards, possibly to provide stability and to compensate for the lost stamen. In the mature flower a basal outgrowth can be found in the position of the lost stamen. However this is more likely to be an outgrowth of the filament sheath rather than a remnant of the lost stamen. These ontogenetic patterns match in parts those found in other Millettieae (unidirectional formation of sepals and stamens, simultaneous petal formation). In contrast, the complete loss of a stamen is rather unusual and supports the isolated position of Abreae and probably justifies (among other characters) its tribal status. A review of androecial characters shows that androecial merosity is on the one hand extremely variable among Leguminosae, varying from a single stamen per flower to more than 500. On the other hand it is noteworthy that the number of stamens becomes stabilised in more derived Papilionoideae such as the large non-protein-amino-acid-accumulating clade (NPAAA clade). This indicates that the androecium has played an important role in the success of a major part of Leguminosae. © 2013 South African Association of Botanists.
Furness C.A.,Jodrell Laboratory
International Journal of Plant Sciences | Year: 2012
The clusioid clade is one of the major subclades identified within the large, diverse rosid order Malpighiales, using molecular data. However, nonmolecular synapomorphies are unclear, and more comparative data are needed to elucidate deep relationships within the order. In this article, pollen and tapetum characters are reevaluated in relation to recent hypotheses of phylogenetic relationships within clusioids. This is done to shed light on the evolution of pollen and tapetum, particularly the evolution of pollen dyads, and also to assess the potential utility of pollen and tapetal characters in the systematics of the clusioids. The comparative morphology of pollen and tapetum is examined in selected taxa from Bonnetiaceae (Bonnetia), Calophylaceae (Caraipa), Clusiaceae (Clusia, Garcinia), Hypericaceae (Hypericum), and Podostemaceae (Podostemum). Pollen and tapetum characters in clusioids and selected outgroups are tabulated, based on both original observations and an extensive literature search, and then optimized onto a recent molecular phylogeny. The optimizations indicate that unusual pollen dispersed as dyads has evolved from monads in the late-branching Podostemoideae (Podostemaceae) clade. Relatively small-sized pollen (E 1/4 11-30 μm) is a potential synapomorphy for Hypericaceae and Podostemaceae, supporting the putative sister relationship between these two families, and pollen with circular or elliptic endoapertures is a potential synapomorphy for Bonnetiaceae. Several pollen characters (size, shape, apertures, and sculpture) indicate that Weddellina (Weddellinoideae: Podostemaceae) is more closely related to Hypericaceae than are Tristichoideae. Irregular granular exines have arisen several times independently within clusioids. A high level of polymorphism occurs in pollen characters in Clusiaceae and is probably related to high levels of diversity in floral morphology, pollination mechanisms, and pollinators, particularly in Clusia and Garcinia. By contrast, pollen of Podostemoideae is relatively uniform, despite developmental differences in microsporogenesis type and the presence of dyads. This may reflect evolutionary canalization or convergent evolution in these enigmatic aquatic plants. © 2012 by The University of Chicago. All rights reserved.