IRLC Research Articles

STM/BP-Like KNOXI Is Uncoupled from ARP in the Regulation of Compound Leaf Development in Medicago truncatula.

Class I KNOTTED-like homeobox (KNOXI) genes are critical for the maintenance of the shoot apical meristem. The expression domain of KNOXI is regulated by ASYMMETRIC LEAVES1/ROUGHSHEATH2/PHANTASTICA (ARP) genes, which are associated with leaf morphology. In the inverted repeat-lacking clade (IRLC) of Fabaceae, the orthologs of LEAFY (LFY) function in place of KNOXI to regulate compound leaf development. Here, we characterized loss-of-function mutants of ARP (PHAN) and SHOOTMERISTEMLESS (STM)- and BREVIPEDICELLUS (BP)-like KNOXI in the model IRLC legume species Medicago truncatula. The function of ARP genes is species specific. The repression of STM/BP-like KNOXI genes in leaves is not mediated by PHAN, and no suppression of PHAN by STM/BP-like KNOXI genes was observed either, indicating that STM/BP-like KNOXI genes are uncoupled from PHAN in M. truncatula. Furthermore, comparative analyses of phenotypic output in response to ectopic expression of KNOXI and the M. truncatula LFY ortholog, SINGLE LEAFLET1 (SGL1), reveal that KNOXI and SGL1 regulate parallel pathways in leaf development. We propose that SGL1 probably functions in a stage-specific manner in the regulation of the indeterminate state of developing leaves in M. truncatula.

The first complete chloroplast genome of the Genistoid legume Lupinus luteus: evidence for a novel major lineage-specific rearrangement and new insights regarding plastome evolution in the legume family.

To date chloroplast genomes are available only for members of the non-protein amino acid-accumulating clade (NPAAA) Papilionoid lineages in the legume family (i.e. Millettioids, Robinoids and the 'inverted repeat-lacking clade', IRLC). It is thus very important to sequence plastomes from other lineages in order to better understand the unusual evolution observed in this model flowering plant family. To this end, the plastome of a lupine species, Lupinus luteus, was sequenced to represent the Genistoid lineage, a noteworthy but poorly studied legume group. The plastome of L. luteus was reconstructed using Roche-454 and Illumina next-generation sequencing. Its structure, repetitive sequences, gene content and sequence divergence were compared with those of other Fabaceae plastomes. PCR screening and sequencing were performed in other allied legumes in order to determine the origin of a large inversion identified in L. luteus. The first sequenced Genistoid plastome (L. luteus: 155 894 bp) resulted in the discovery of a 36-kb inversion, embedded within the already known 50-kb inversion in the large single-copy (LSC) region of the Papilionoideae. This inversion occurs at the base or soon after the Genistoid emergence, and most probably resulted from a flip-flop recombination between identical 29-bp inverted repeats within two trnS genes. Comparative analyses of the chloroplast gene content of L. luteus vs. Fabaceae and extra-Fabales plastomes revealed the loss of the plastid rpl22 gene, and its functional relocation to the nucleus was verified using lupine transcriptomic data. An investigation into the evolutionary rate of coding and non-coding sequences among legume plastomes resulted in the identification of remarkably variable regions. This study resulted in the discovery of a novel, major 36-kb inversion, specific to the Genistoids. Chloroplast mutational hotspots were also identified, which contain novel and potentially informative regions for molecular evolutionary studies at various taxonomic levels in the legumes. Taken together, the results provide new insights into the evolutionary landscape of the legume plastome.

Evolutionary and biotechnology implications of plastid genome variation in the inverted‐repeat‐lacking clade of legumes

Land plant plastid genomes (plastomes) provide a tractable model for evolutionary study in that they are relatively compact and gene dense. Among the groups that display an appropriate level of variation for structural features, the inverted-repeat-lacking clade (IRLC) of papilionoid legumes presents the potential to advance general understanding of the mechanisms of genomic evolution. Here, are presented six complete plastome sequences from economically important species of the IRLC, a lineage previously represented by only five completed plastomes. A number of characters are compared across the IRLC including gene retention and divergence, synteny, repeat structure and functional gene transfer to the nucleus. The loss of clpP intron 2 was identified in one newly sequenced member of IRLC, Glycyrrhiza glabra. Using deeply sequenced nuclear transcriptomes from two species helped clarify the nature of the functional transfer of accD to the nucleus in Trifolium, which likely occurred in the lineage leading to subgenus Trifolium. Legumes are second only to cereal crops in agricultural importance based on area harvested and total production. Genetic improvement via plastid transformation of IRLC crop species is an appealing proposition. Comparative analyses of intergenic spacer regions emphasize the need for complete genome sequences for developing transformation vectors for plastid genetic engineering of legume crops.

Synthesis, docking and evaluation of antioxidant and antimicrobial activities of novel 1,2,4-triazolo[3,4-b][1,3,4]thiadiazol-6-yl)selenopheno[2,3-d]pyrimidines

A series of 1,2,4-(triazolo[3,4-b][1,3,4]thiadiazol-6-yl)selenopheno[2,3-d]pyrimidines (10a–j) were synthesized with various substituted anilines and benzoic acids. Structures of newly synthesized compounds were established by IR, 1H &13C NMR and LC–MS spectral data. The antioxidant activity of the synthesized compounds was evaluated by DPPH, NO and H2O2 radical scavenging methods. The newly synthesized compounds were evaluated for their antimicrobial activity against Gram +ve and Gram −ve bacteria and antifungal activity by well diffusion method. Compounds 10d, 10h and 10i showed promising antioxidant, antibacterial as well as antifungal activity and these were found to be the most potent activity molecules when compared with that of standard drugs. Molecules docking studies have been performed on Staphylococcus aureus (SA) of Gram +ve bacteria.

Regulation of Compound Leaf Development in Medicago truncatula by Fused Compound Leaf1, a Class M KNOX Gene

Medicago truncatula is a legume species belonging to the inverted repeat lacking clade (IRLC) with trifoliolate compound leaves. However, the regulatory mechanisms underlying development of trifoliolate leaves in legumes remain largely unknown. Here, we report isolation and characterization of fused compound leaf1 (fcl1) mutants of M. truncatula. Phenotypic analysis suggests that FCL1 plays a positive role in boundary separation and proximal-distal axis development of compound leaves. Map-based cloning indicates that FCL1 encodes a class M KNOX protein that harbors the MEINOX domain but lacks the homeodomain. Yeast two-hybrid assays show that FCL1 interacts with a subset of Arabidopsis thaliana BEL1-like proteins with slightly different substrate specificities from the Arabidopsis homolog KNATM-B. Double mutant analyses with M. truncatula single leaflet1 (sgl1) and palmate-like pentafoliata1 (palm1) leaf mutants show that fcl1 is epistatic to palm1 and sgl1 is epistatic to fcl1 in terms of leaf complexity and that SGL1 and FCL1 act additively and are required for petiole development. Previous studies have shown that the canonical KNOX proteins are not involved in compound leaf development in IRLC legumes. The identification of FCL1 supports the role of a truncated KNOX protein in compound leaf development in M. truncatula.

Bacteroid Development in Legume Nodules: Evolution of Mutual Benefit or of Sacrificial Victims?

Symbiosomes are organelle-like structures in the cytoplasm of legume nodule cells which are composed of the special, nitrogen-fixing forms of rhizobia called bacteroids, the peribacteroid space and the enveloping peribacteroid membrane of plant origin. The formation of these symbiosomes requires a complex and coordinated interaction between the two partners during all stages of nodule development as any failure in the differentiation of either symbiotic partner, the bacterium or the plant cell prevents the subsequent transcriptional and developmental steps resulting in early senescence of the nodules. Certain legume hosts impose irreversible terminal differentiation onto bacteria. In the inverted repeat-lacking clade (IRLC) of legumes, host dominance is achieved by nodule-specific cysteine-rich peptides that resemble defensin-like antimicrobial peptides, the known effector molecules of animal and plant innate immunity. This article provides an overview on the bacteroid and symbiosome development including the terminal differentiation of bacteria in IRLC legumes as well as the bacterial and plant genes and proteins participating in these processes.

Characteristics of Bacteroids in Indeterminate Nodules of the Leguminous Tree Leucaena glauca

Rhizobia establish symbiosis with legumes. Bacteroids in indeterminate nodules of Inverted Repeat Lacking Clade (IRLC) legumes undergo terminal differentiation caused by Nodule-specific Cysteine-Rich peptides (NCRs). Microscopic observations of bacteroids and the detection of NCRs in indeterminate nodules of the non-IRLC legume Leucaena glauca were performed. A portion of the bacteroids showed moderate cell elongation, loss of membrane integrity, and multiple nucleoids. The symbiosome contained multiple bacteroids and NCR-like peptides were not detectable. These results indicate that bacteroid differentiation in L. glauca is different from that in IRLC legumes although both hosts form indeterminate nodules.

Floral ontogeny in Wisteria sinensis (Fabaceae: Faboideae: Millettieae) and its systematic implications

Floral organogenesis and development of the bushy perennial legume Wisteria sinensis (Millettieae, Fabaceae) were studied by epi-illumination light-microscopy techniques. Zygomorphic flowers of W. sinensis were arranged in alternating pentamerous whorls. The order of organogenesis in each whorl was unidirectional, except for the outer antesepalous stamens, which were initiated bidirectionally, starting on the lateral side. Unusual developmental features for the family included the formation of common primordia, comprised of the petal and the corresponding abaxial antepetalous stamen and the temporal overlap of corolla, androecium and carpel organ initiation. Unusual features during late development included formation of nectar windows and a wet stigma. The floral ontogeny of W. sinensis was more similar to that of other genera from the inverted-repeat-lacking clade (IRLC) than to the floral ontogeny of other Millettieae that have been investigated.

Compound leaf development and evolution in the legumes.

Across vascular plants, Class 1 KNOTTED1-like (KNOX1) genes appear to play a critical role in the development of compound leaves. An exception to this trend is found in the Fabaceae, where pea (Pisum sativum) uses UNIFOLIATA, an ortholog of the floral regulators FLORICAULA (FLO) and LEAFY (LFY), in place of KNOX1 genes to regulate compound leaf development. To assess the phylogenetic distribution of KNOX1-independent compound leaf development, a survey of KNOX1 protein expression across the Fabaceae was undertaken. The majority of compound-leafed Fabaceae have expression of KNOX1 proteins associated with developing compound leaves. However, in a large subclade of the Fabaceae, the inverted repeat-lacking clade (IRLC), of which pea is a member, KNOX1 expression is not associated with compound leaves. These data suggest that the FLO/LFY gene may function in place of KNOX1 genes in generating compound leaves throughout the IRLC. The contribution of FLO/LFY to leaf complexity in a member of the Fabaceae outside of the IRLC was examined by reducing expression of FLO/LFY orthologs in transgenic soybean (Glycine max). Transgenic plants with reduced FLO/LFY expression showed only slight reductions in leaflet number. Overexpression of a KNOX1 gene in alfalfa (Medicago sativa), a member of the IRLC, resulted in an increase in leaflet number. This implies that KNOX1 targets, which promote compound leaf development, are present in alfalfa and are still sensitive to KNOX1 regulation. These data suggest that KNOX1 genes and the FLO/LFY gene may have played partially overlapping roles in compound leaf development in ancestral Fabaceae but that the FLO/LFY gene took over this role in the IRLC.

Systematics of Sitonini (Coleoptera: Curculionidae: Entiminae), with a hypothesis on the evolution of feeding habits

AbstractA new classification of Sitonini Gistel into ten genera is proposed, derived from a phylogenetic analysis based on morphology. Two subgenera ofSitona,CharagmusandCoelositona, are promoted to genus level.Sitonais restricted to the former nominotypical subgenus and redefined using apomorphies, and several species previously included in it are transferred to the genusCoelositonaGonzález. The species composition of the genusCharagmusSchönherr is unchanged.Andriongen.n.is described (type species:Curculio regensteinensisHerbst, 1794).CatachaenusSchönherr, 1840 is synonymized withEugnathusSchönherr, 1834 (syn.n.).Homalorhinus lutosusHochhuth, 1847 is removed from Sitonini. The relationships represented by the new classification correspond with the evolution of Fabaceae (Leguminosae), mostly with the group of ‘temperate herbaceous tribes’ or Hologalegina. This group is divided into the sister clades, Loteae s.l. and IRLC (inverted repeat‐lacking clade) – a clade well defined by the loss of a structural mutation in the genome of the chloroplast.Andriondoes not feed on Hologalegina.CharagmusandCoelositonafeed on species of Loteae s.l., whereas members of the genusSitonafeed on species in IRLC. This ability to feed on IRLC plants seems to have been a key trait that enabled the radiation ofSitonainto more than 100 species. A key to the genera of Sitonini and illustrations of important morphological features are provided. A new structure is described from the internal sac, the ‘hamuli’. The variability of hamuli between the species of Sitonini is an important new tool in the taxonomy of this tribe. New combinations:Eugnathus circulus(Eydoux & Souleyet, 1839),E. mangarinicus(Voss, 1925),E. scintillans(Pascoe, 1874),E. sulcifrons(Heller, 1934),Charagmus gressorius(Fabricius, 1792),Ch. intermediusKüster, 1847,Ch. griseus(Fabricius, 1775),Ch. cachectusGyllenhal, 1834,Ch. stierliniReitter, 1903,Ch. variegatus(Fåhraeus, 1840),Coelositona ribesi(González, 1971),C. cambricus(Stephens, 1831),C. cinerascens(Fåhraeus, 1840),C. limosus(Rossi, 1792),C. ocellatus(Küster, 1849),C. latipennis(Gyllenhal, 1834),C. puberulus(Reitter, 1903),C. villosus(Allard, 1869),Andrion regensteinense(Herbst, 1794) andAnemeroides lutosus(Hochhuth, 1847).

A phylogeny of legumes (Leguminosae) based on analysis of the plastidmatKgene resolves many well‐supported subclades within the family

Phylogenetic analysis of 330 plastid matK gene sequences, representing 235 genera from 37 of 39 tribes, and four outgroup taxa from eurosids I supports many well-resolved subclades within the Leguminosae. These results are generally consistent with those derived from other plastid sequence data (rbcL and trnL), but show greater resolution and clade support overall. In particular, the monophyly of subfamily Papilionoideae and at least seven major subclades are well-supported by bootstrap and Bayesian credibility values. These subclades are informally recognized as the Cladrastis clade, genistoid sensu lato, dalbergioid sensu lato, mirbelioid, millettioid, and robinioid clades, and the inverted-repeat-lacking clade (IRLC). The genistoid clade is expanded to include genera such as Poecilanthe, Cyclolobium, Bowdichia, and Diplotropis and thus contains the vast majority of papilionoids known to produce quinolizidine alkaloids. The dalbergioid clade is expanded to include the tribe Amorpheae. The mirbelioids include the tribes Bossiaeeae and Mirbelieae, with Hypocalypteae as its sister group. The millettioids comprise two major subclades that roughly correspond to the tribes Millettieae and Phaseoleae and represent the only major papilionoid clade marked by a macromorphological apomorphy, pseudoracemose inflorescences. The robinioids are expanded to include Sesbania and members of the tribe Loteae. The IRLC, the most species-rich subclade, is sister to the robinioids. Analysis of the matK data consistently resolves but modestly supports a clade comprising papilionoid taxa that accumulate canavanine in the seeds. This suggests a single origin for the biosynthesis of this most commonly produced of the nonprotein amino acids in legumes.