Cotyledon areoles in Bobgunnia (Fabaceae: Swartzieae)

Cotyledon areoles, a seed character unique to papilionoid legumes, are reported for the first time in the legume tribe Swartzieae, an anomalous group sometimes considered to be intermediate between subfamilies Caesalpinioideae and Papilionoideae. Bobgunnia madagascariensis has a linear, slightly branched cotyledon areole on the abaxial surface of each cotyledon. Previous reports of other papilionoid seed features in this species are confirmed and extended. These highly distinctive papilionoid seed structures, and recent reports from floral ontogeny and molecular systematics which show Bobgunnia to be closely related to Swartzia and several other genera of Swartzieae, add further evidence to assertions that Swartzia seed structures are derived by simplification from a papilionoid seed, and not by retention of less specialized caesalpinioid seed features. The function and evolutionary advantage of cotyledon areoles are unknown and need investigation. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 287–291.     

Endopolyploidy, Cell Volume and Nuclear Volume Interrelationships in Cotyledons of the Leguminosae

Cotyledon nuclei of most legume species did not stain adequatelywith the Feulgen reaction and so an indirect method based onthe relationship between DNA content, nuclear volume and cellvolume was used for the detection of endopolyploidy. Cotyledonendopolyploidy was not found in the Caesalpinioideae and wasinfrequent in the Mimosoideae. In the Papilionoideae it wasfound in taxa at several levels. It probably occurs throughoutthe tribes Vicieae and Cicereae and in most genera of the Phaseoleae;elsewhere it is confined to particular genera within tribes,such as Arachis in the Aeschynomeneae and Lupinus in the Genisteae.Endopolyploidy shows correlation with cotyledon anatomy aridfunction in that it is confined to cotyledons whose main oronly function is storage, and has so far not been found in foliarcotyledons. Endopolyploidy, cell volume, nuclear volume, cotyledon, Leguminosae     

Root nodules of some tropical legumes in Singapore

Summary A survey of 35 legume species comprising 25 of Papilionoideae, 7 of Mimosoideae and 3 of Caesalpinioideae was made. Nodulation was found in all the species except for 2 (Caesalpinnia pulcherrima and Cassia siamea) of Caesalpinioideae, both of which possessed dark coloured roots. Nodulation is reported for the first time for Adenanthera pavonina and Delonix regia. Nodule shapes were described and classified into different types. The isolates of rhizobia obtained belonged largely to the slow growing group (17 isolates) isolated mainly from members of Papilionoideae; some belonged to the fast growing group (14 isolates), and only 3 isolates belonged to the very slow growing group. The slow growing group isolates were confirmed to be cowpea type rhizobia on the basis of positive nodulation with cowpea plants. re]19750829     

Is the Legume Nodule a Modified Root or Stem or an Organ sui generis?

The legume nodule, which houses nitrogen-fixing rhizobia, is a unique plant organ. Its homology with lateral roots has been inferred by a comparison with other nitrogen-fixing nodules, especially those formed on actinorhizal plants in response to Frankia inoculation or on Parasponia roots following inoculation with Bradyrhizobium species. These nodules are clearly modified lateral roots in terms of their structure and development. However, legume nodules differ from lateral roots and these other nodules in their developmental origin, anatomy, and patterns of gene expression, and, consequently, several other evolutionary derivations, including from stems, wound or defense responses, or the more ancient vesicular-arbuscular mycorrhizal symbiosis, have been postulated for the legume nodule. In this review, we first present a broad view of the legume family showing the diversity of nodulation occurrence and types in the different subfamilies and particularly within the subfamily Papilionoideae. We then define the typological and molecular criteria used to discriminate the basic organs — root, stem, leaf— of the plant. Finally, we discuss the possible origins of the legume nodule in terms of these typological and molecular bases.     

New aspects in floral development of Papilionoideae: initiated but suppressed bracteoles and variable initiation of sepals

BACKGROUND AND AIMS: The increase of molecular data and the resulting insights into legume systematics make the search for new morphological characters and a careful re-investigation of already stated characters necessary. Bracteoles are small, reduced leaves borne close to the base of lateral branches. Although they seem unimportant in older buds, they have an ecological function in protecting the sepal primordia. Furthermore, a morphogenetic function in mediating the onset of sepal initiation is suspected in the literature. The occurrence of bracteoles varies within Papilionoideae, and their distribution is used in legume systematics. But this is open to criticism, because there is a tendency to use 'absent' for 'caducous'. Thus attention here was paid to the initiation of bracteoles as well as to the sequence of sepal initiation. METHODS: The floral development of 30 taxa out of 15 tribes of Papilionoideae was investigated using scanning electron microscopy (SEM). KEY RESULTS: In five taxa the bracteoles initiated, but suppressed early. Furthermore, a broad variability of sepal initiation was found. Besides the widely stated unidirectional pattern, modified unidirectionality, tendencies towards whorled, fully whorled, bidirectional and successive initiation of sepals were all found. CONCLUSION: Initiated but suppressed bracteoles are presented as a 'new' character in Papilionoideae. Considering the presence of bracteoles as a plesiomorphy, their suppression can be seen as a step towards completely reduced bracteoles. The remarkable variability of the sequence of sepal initiation questions the widely stated unidirectionality of organ initiation in Papilionoideae. The different modes of sepal initiation are deducible from the helical pattern of some caesalpinioids, which is seen as a developmental link of the flowers of Papilionoideae and Caesalpinioideae. The bidirectional sepal initiation is possibly a consequence of the morphogenetic function of bracteoles, although bidirectionality is not found in all taxa with reduced bracteoles.     

Genetic differentiation of groundnut seed-beetle populations in Senegal

Caryedon serratus, the groundnut seed-beetle, is a major pest of groundnut (Arachis hypogaea), an introduced legume in the subfamily Papilionoideae. Native hosts of C. serratus in Senegal include Bauhinia rufescens, Cassia sieberiana, Piliostigma reticulatum and Tamarindus indica, all of which belong to the legume subfamily Caesalpinioideae.The biology and natural history of C. serratus suggest that it is a candidate for population differentiation via host-race formation. Evidence for host-tree associated differentiation in C. serratus would be important for the design of rational pest management practices.To test this possibility, we analyzed the genetic structure of 20 adult collections of C. serratus from six sites in Western Senegal, on its five hosts. Results show a strong differentiation of insects from different host trees, with specimens from C. sieberiana possibly representing a sibling species and insects from B. rufescens a distinct host-race.     

Legume phylogeny and the evolution of a unique contractile apparatus that regulates phloem transport

Protein bodies called forisomes undergo Ca(2+)-dependent deformations to occlude sieve tubes reversibly, providing a unique regulatory mechanism of phloem transport. Because forisomes are known exclusively from the Papilionoideae (Leguminosae), the evolution of forisome function may have played a role in the rapid radiation of this huge taxon. The unexpected discovery of a papilionoid species lacking forisomes led us to evaluate a representative set of species covering 33 of the 36 legume tribes traditionally recognized. We found forisomes in Papilionoideae but not in Caesalpinioideae and Mimosoideae. Forisomes were absent from several species of the papilionoid tribe Galegeae. Forisomes with tail-like protrusions occurred less frequently than tailless ones; their distribution correlated with taxonomic units but not sharply enough to render forisome type a reliable criterion for classification. Thus, the distribution of forisome types appeared to reflect physiological variability in the pathways of forisome assembly rather than the evolution of forisome genes. On the other hand, Ca(2+)-dependent forisome deformation and sieve tube plugging occurred in Bobgunnia madagascariensis, a member of the swartzioid clade that presumably is the sister group of all other papilionoids, suggesting that forisomes and their unique mechanism of deformation are a synapomorphy of the Papilionoideae.     

Nodulation of legume trees from South East Brazil

Summary An extended survey of nodulation of legume trees from South-East Brazilian forests was conducted. Six new species from the Caesalpinioideae, 23 from the Mimosoideae and 27 from the Papilionoideae are reported to have nodules. Nitrogenase activity (acetylene reduction) was tested for all nodules and rhizobia were isolated from the most active.     

Toward a new concept of the evolution of symbiotic nitrogen fixation in the Leguminosae

It is generally believed that only the nodulating species of the Leguminosae fix atmospheric nitrogen; however, anatomical, ecological and taxonomic considerations indicate that non-nodulating legume species may also fix nitrogen. To test whether nitrogen-fixing symbioses in the Leguminosae might extend to the non-nodulating species, a survey of the Leguminosae was conducted: living plants of non-nodulating species were assayed using acetylene reduction. Ethylene evolution, indicating apparent nitrogenase activity, was detected in non-nodulating species representing the major taxonomic groups of Caesalpinioideae as well as in non-nodulating species of the Papilionoideae and Mimosoideae. Non-nodules nitrogen fixation appears to have provided evolutionary precursors for the nodular symbiosis in the Leguminosae.     

Broad screening of the legume family for variability in seed insecticidal activities and for the occurrence of the A1b-like knottin peptide entomotoxins

Pea albumin 1b (PA1b) is a small sulphur-rich peptide from pea seeds, also named leginsulin because of the binding characteristics of its soybean orthologue. Its insecticidal properties were discovered more recently. By using a combination of molecular, biochemical and specific insect bioassays on seed extracts, we characterised genes from numerous Papilionoideae, but not from Caesalpinioideae or Mimosoideae, although the last group harboured species with partially positive cues (homologous biological activities). The A1b defence peptide family, therefore, appears to have evolved relatively late in the legume lineage, maybe from the sophoroid group (e.g. Styphnolobium japonicum). However, unambiguous sequence information is restricted to a group of tribes within the subfamily Papilionoideae (Psoraleae, Millettieae, Desmodieae, Hedysareae, Phaseoleae, Vicieae, and the now clearly polyphyletic "Trifolieae" and "Galegeae"). Recent diversification by gene duplications has occurred in many species, or longer ago in some lineages (Medicago truncatula), as well as probable gene or expression losses at different taxonomic levels (Loteae, Vigna subterranea).     

The Complete Sequence of the Acacia ligulata Chloroplast Genome Reveals a Highly Divergent clpP1 Gene

Legumes are a highly diverse angiosperm family that include many agriculturally important species. To date, 21 complete chloroplast genomes have been sequenced from legume crops confined to the Papilionoideae subfamily. Here we report the first chloroplast genome from the Mimosoideae, Acacia ligulata, and compare it to the previously sequenced legume genomes. The A. ligulata chloroplast genome is 158,724 bp in size, comprising inverted repeats of 25,925 bp and single-copy regions of 88,576 bp and 18,298 bp. Acacia ligulata lacks the inversion present in many of the Papilionoideae, but is not otherwise significantly different in terms of gene and repeat content. The key feature is its highly divergent clpP1 gene, normally considered essential in chloroplast genomes. In A. ligulata, although transcribed and spliced, it probably encodes a catalytically inactive protein. This study provides a significant resource for further genetic research into Acacia and the Mimosoideae. The divergent clpP1 gene suggests that Acacia will provide an interesting source of information on the evolution and functional diversity of the chloroplast Clp protease complex.     

Determinism of carbon and nitrogen reserve accumulation in legume seeds

In legume plants, the determination of individual seed weight is a complex phenomenon that depends on two main factors. The first one corresponds to the number of cotyledon cells, which determines the potential seed weight as the cotyledon cell number is related to seed growth rate during seed filling. Since cell divisions take place between flowering and the beginning of seed filling, any stress occurring before the beginning of seed filling can affect individual seed growth rate (C and N reserve accumulation in seeds), and thus individual seed weights. The second factor concerns carbon and nitrogen supply to the growing seed to support reserve accumulation. Grain legume species produce protein-rich seeds involving high requirement of nitrogen. Since seed growth rate as determined by cotyledon cell number is hardly affected by photoassimilate availability during the filling period, a reduction of photosynthetic activity caused by nitrogen remobilization in leaves (e.g., remobilization of essential proteins involved in photosynthesis) can lead to shorten the duration of the filling period, and by that can provoke a limitation of individual seed weights. Accordingly, any biotic or abiotic stress during seed filling causing a decrease in photosynthetic activity should lead to a reduction of the duration of seed filling.     

A new species Megabruchidius sophorae (Coleoptera, Bruchidae), feeding on seeds of Styphnolobium (Fabaceae) new to Bruchidae

A new species Megabruchidiussophorae (Insecta, Coleoptera) is described from Japan (Honshu). The larval host of this bruchid is the seeds of the tree legume 'enju', or chinese scholar tree, Styphnolobium japonicum (a senior synonym of Sophora japonica), which is a new host genus to Bruchidae. Styphnolobium is positioned basally in molecular phylogeny of the leguminous subfamily Papilionoideae. Other members of Megabruchidius are known to feed on Gleditsia, the tree legumes that belong to the most ancestral subfamily Caesalpinioideae. Therefore, Megabruchidius utilizes ancestral groups of legumes as its host plants. Megabruchidius has been inferred to be ancestral, based on its behavior. The character state of the host for this third Megabruchidius species supports that the genus is ancestral, at least in the subfamily Bruchinae. We also reviewed the genera closely related to Megabruchidius, i.e., Bruchidius and Sulcobruchus in Bruchidini, and wrote a key to the species in the genus Megabruchidius.     

How and why does the areole meristem move in Echinocereus (Cactaceae)?

Background and Aims In Cactaceae, the areole is the organ that forms the leaves, spines and buds. Apparently, the genus Echinocereus develops enclosed buds that break through the epidermis of the stem adjacent to the areole; this trait most likely represents a synapomorphy of Echinocereus. The development of the areole is investigated here in order to understand the anatomical modifications that lead to internal bud development and to supplement anatomical knowledge of plants that do not behave according to classical shoot theory.Methods The external morphology of the areole was documented and the anatomy was studied using tissue clearing, scanning electron microscopy and light microscopy for 50 species that represent the recognized clades and sections of the traditional classification of the genus, including Morangaya pensilis (Echinocereus pensilis).Key Results In Echinocereus, the areole is sealed by the periderm, and the areole meristem is moved and enclosed by the differential growth of the epidermis and surrounding cortex. The enclosed areole meristem is differentiated in a vegetative or floral bud, which develops internally and breaks through the epidermis of the stem. In Morangaya pensilis, the areole is not sealed by the periderm and the areole meristem is not enclosed.Conclusions The enclosed areole meristem and internal bud development are understood to be an adaptation to protect the meristem and the bud from low temperatures. The anatomical evidence supports the hypothesis that the enclosed bud represents one synapomorphy for Echinocereus and also supports the exclusion of Morangaya from Echinocereus.     

我国豆科树种结瘤调查(续)

据国内资料报道,我国豆科树种约94属763种,已调查过结瘤状况的有含羞草亚科的123种(包括近几年来从国外引种的54种)、蝶形花亚科的211种和苏木亚科的70种,其中可以结瘤的有含羞草亚科的116种、蝶形花亚科的207种和苏木亚科的18种。含羞草亚科中的2种、蝶形花亚科中的3种均有结瘤和不结瘤的报道。     

我国豆科树种结瘤调查

据国内资料报道,我国豆科树种约94属763种,已调查过结瘤状况的有含羞草亚科的123种(包括近几年来从国外引种的54种)、蝶形花亚科的211种和苏木亚科的70种,其中可以结瘤的有含羞草亚科的116种、蝶形花亚科的207种和苏木亚科的18种。含羞草亚科中的2种、蝶形花亚科中的3种均有结瘤和不结瘤的报道。     

The chicken or the egg? Plastome evolution and an independent loss of the inverted repeat in papilionoid legumes

The plastid genome (plastome), while surprisingly constant in gene order and content across most photosynthetic angiosperms, exhibits variability in several unrelated lineages. During the diversification history of the legume family Fabaceae, plastomes have undergone many rearrangements, including inversions, expansion, contraction and loss of the typical inverted repeat (IR), gene loss and repeat accumulation in both shared and independent events. While legume plastomes have been the subject of study for some time, most work has focused on agricultural species in the IR-lacking clade (IRLC) and the plant model Medicago truncatula. The subfamily Papilionoideae, which contains virtually all of the agricultural legume species, also comprises most of the plastome variation detected thus far in the family. In this study three non-papilioniods were included among 34 newly sequenced legume plastomes, along with 33 publicly available sequences, to assess plastome structural evolution in the subfamily. In an effort to examine plastome variation across the subfamily, approximately 20% of the sampling represents the IRLC with the remainder selected to represent the early-branching papilionoid clades. A number of IR-related and repeat-mediated changes were identified and examined in a phylogenetic context. Recombination between direct repeats associated with ycf2 resulted in intraindividual plastome heteroplasmy. Although loss of the IR has not been reported in legumes outside of the IRLC, one genistoid taxon was found to completely lack the typical plastome IR. The role of the IR and non-IR repeats in the progression of plastome change is discussed.     

Plastid genome sequences of legumes reveal parallel inversions and multiple losses of rps16 in papilionoids

To date, publicly available plastid genomes of legumes have for the most part been limited to the subfamily Papilionoideae. Here we report 13 new plastid genomes of legumes spanning all three subfamilies. The genomes representing Caesalpinioideae and Mimosoideae are highly conserved in gene content and gene order, similar to the ancestral angiosperm genome organization. Genomes within the Papilionoideae, however, have reduced sizes due to deletions in nine intergenic spacers primarily in the large single copy region. Our study also indicates that rps16 has been independently lost at least five times in legumes, with additional gene and intron losses scattered among the papilionoids. Additionally, genera from two distinct lineages within the papilionoids, Lupinus and Robinia, have a parallel inversion of 36 and 39 kb, respectively. This parallel inversion is novel as it appears to be caused by a 29 bp repeat within two trnS genes. This repeat is present in all available legume plastid genomes indicating that there is the potential for this inversion to be present in more species. This case of a homoplasious inversion is also evidence that some inversion events may not be reliable phylogenetic markers.     

CHROMOSOME NUMBERS IN THE LEGUMINOSAE II: AFRICAN SPECIES,INCLUDING PHYLETIC INTERPRETATIONS

Turner , B. L., and O. S. Fearing . (U. Texas, Austin.) Chromosome numbers in the Leguminosae. II. African species, including phyletic interpretations. Amer. Jour. Bot. 46(1) : 49-57. Illus. 1959.—Chromosome numbers for 30 African legume species have been reported. These include first reports for 28 taxa, including 12 genera (Bolusanthus, Calpurnia, Melolobium, Lessertia, Sulherlandia, Colophospermum, Guibourtia, Burkea, Julbernardia, Schotia, Piliostigma and Swartzia). The counts are discussed with respect to those previously reported for related groups, and this chromosomal information was used to construct hypothetical phyletic lines at the tribal level within the subfamilies Papilionoideae and Caesalpinioideae. A phyletic scheme for the Leguminosae (excluding the Mimosoideae) based on this evidence from chromosome studies is presented. Notable departures from previously suggested phyletic treatments include: (1) Suggestion for inclusion of genera of the Galegeae and Hedysareae with base numbers of x = 10 and 11 with the Phaseoleae and Dalbergieae. (2) Derivation of the Papilionoideae through caesalpinoid prototypes, possibly from Swartzia-like ancestors. (3) Recognition of several very old chromosomal lines stemming from the subfamily Caesalpinioideae, and the suggestion that parts of the tribes Sclerolobieae, Cynometreae, Swartzieae and Sophoreae are, perhaps, more closely related to each other and to the Papilionoideae than they are to the remaining caesalpinoid tribal lines.     

Revisiting the phylogeny of papilionoid legumes: New insights from comprehensively sampled early-branching lineages

• Premise of study: Phylogenetic relationships of the papilionoid legumes (Papilionoideae) reveal that the early branches are more highly diverse in floral morphology than are other clades of Papilionoideae. This study attempts for the first time to comprehensively sample the early-branching clades of this economically and ecologically important legume subfamily and thus to resolve relationships among them. • Methods: Parsimony and Bayesian phylogenetic analyses of the plastid matK and trnL intron sequences included 29 genera not yet sampled in matK phylogenies of the Papilionoideae, 11 of which were sampled for DNA sequence data for the first time. • Key results: The comprehensively sampled matK phylogeny better resolved the deep-branching relationships and increased support for many clades within Papilionoideae. The potentially earliest-branching papilionoid clade does not include any genus traditionally assigned to tribe Swartzieae. Dipterygeae is monophyletic with the inclusion of Monopteryx. The genera Aldina and Amphimas represent two of the nine main but as yet unresolved lineages comprising the large 50-kb inversion clade within papilionoids. The quinolizidine-alkaloid-accumulating genistoid clade is expanded to include a strongly supported subclade containing Ormosia and the previously unplaced Clathrotropis s.s., Panurea, and Spirotropis. Camoensia is the first-branching genus of the core genistoids. • Conclusions: The well-resolved phylogeny of the earliest-branching papilionoids generated in this study will greatly facilitate the efforts to redefine and stabilize the classification of this legume subfamily. Many key floral traits did not often predict phylogenetic relationships, so comparative studies on floral evolution and plant–animal interactions, for example, should also benefit from this study.