Nesaecrepida infuscata: a biological control agent of the invasive plant Mimosa pigra

Mimosa pigra L. is a serious weed of wetlands of Australia, Asia and Africa. A suite of established biocontrol agents have been introduced in Australia and some Asian countries, but better control is needed. Nesaecrepida infuscata (Schaeffer) (Coleoptera: Chrysomelidae) is a common insect on M. pigra in tropical America. The larvae develop on the roots while the adults feed on the leaves. As both roots and leaves of M. pigra are relatively undamaged in the introduced range, this species has potential to limit the growth, survival and seed production. Furthermore, it is abundant in the dry season and so inflicts damage when most other agents are not active. In host specificity tests, larvae did not develop on any of the 65 test plant species other than M. pigra. Adult feeding on test plant species other than M. pigra was minimal. Based on these results, this insect has been released in Australia.     

Nodule Symbiosis of Invasive <Emphasis Type="Italic">Mimosa pigra</Emphasis> in Australia and in Ancestral Habitats: A Comparative Analysis

Ninety isolates of root nodule bacteria from an invasive Mimosa pigra population in Australia were characterized by PCR assays and by sequencing of ribosomal genes. All isolates belonged to the same bacterial genus (Burkholderia) that predominates on M. pigra in its native geographic range in tropical America. However, the Australian Burkholderia strains represented several divergent lineages, none of which had a close relationship to currently known Burkholderia strains in American M. pigra populations. Inoculation of M. pigra with Australian strains resulted in equal or higher plant growth and nodule nitrogenase activity (measured by acetylene reduction assays) relative to outcomes with bacteria from M. pigra’s native geographic region. The main difference in symbiotic phenotype for bacteria from the two regions involved responses to an alternate Mimosa host species: Central American strains failed to fix nitrogen in association with Mimosa pudica, while most Australian Burkholderia isolates tested had high nodule nitrogenase activity in association with both Mimosa species. Invasive M. pigra populations in Australia have therefore acquired a diverse assemblage of nodule bacteria that are effective nitrogen-fixing symbionts, despite having a broader host range and a distant genetic relationship to bacterial strains found in the plant’s ancestral region.     

Coexistence of Burkholderia, Cupriavidus, and Rhizobium sp. Nodule Bacteria on two Mimosa spp. in Costa Rica

rRNA gene sequencing and PCR assays indicated that 215 isolates of root nodule bacteria from two Mimosa species at three sites in Costa Rica belonged to the genera Burkholderia, Cupriavidus, and Rhizobium. This is the first report of Cupriavidus sp. nodule symbionts for Mimosa populations within their native geographic range in the neotropics. Burkholderia spp. predominated among samples from Mimosa pigra (86% of isolates), while there was a more even distribution of Cupriavidus, Burkholderia, and Rhizobium spp. on Mimosa pudica (38, 37, and 25% of isolates, respectively). All Cupriavidus and Burkholderia genotypes tested formed root nodules and fixed nitrogen on both M. pigra and M. pudica, and sequencing of rRNA genes in strains reisolated from nodules verified identity with inoculant strains. Inoculation tests further indicated that both Cupriavidus and Burkholderia spp. resulted in significantly higher plant growth and nodule nitrogenase activity (as measured by acetylene reduction assays) relative to plant performance with strains of Rhizobium. Given the prevalence of Burkholderia and Cupriavidus spp. on these Mimosa legumes and the widespread distribution of these plants both within and outside the neotropics, it is likely that both β-proteobacterial genera are more ubiquitous as root nodule symbionts than previously believed.     

Color Vision Variation as Evidenced by Hybrid L/M Opsin Genes in Wild Populations of Trichromatic Alouatta New World Monkeys

Platyrrhine (New World) monkeys possess highly polymorphic color vision owing to allelic variation of the single-locus L/M opsin gene on the X chromosome. Most species consist of female trichromats and female and male dichromats. Howlers (genus Alouatta) are an exception; they are considered to be routinely trichromatic with L and M opsin genes juxtaposed on the X chromosome, as seen in catarrhine primates (Old World monkeys, apes, and humans). Yet it is not known whether trichromacy is invariable in howlers. We examined L/M opsin variation in wild howler populations in Costa Rica and Nicaragua (Alouatta palliata) and Belize (A. pigra), using fecal DNA. We surveyed exon 5 sequences (containing the diagnostic 277th and 285th residues for λ_max) for 8 and 18 X chromosomes from Alouatta palliata and A. pigra, respectively. The wavelengths of maximal absorption (λ_max) of the reconstituted L and M opsin photopigments were 564 nm and 532 nm, respectively, in both species. We found one M–L hybrid sequence with a recombinant 277/285 haplotype in Alouatta palliata and two L–M hybrid sequences in A. pigra. The λ_max values of the reconstituted hybrid photopigments were in the range of 546~554 nm, which should result in trichromat phenotypes comparable to those found in other New World monkey species. Our finding of color vision variation due to high frequencies of L/M hybrid opsin genes in howlers challenges the current view that howlers are routine and uniform trichromats. These results deepen our understanding of the evolutionary significance of color vision polymorphisms and routine trichromacy and emphasize the need for further assessment of opsin gene variation as well as behavioral differences among subtypes of trichromacy.     

Malacorhinus irregularis for biological control of Mimosa pigra: host-specificity,life cycle,and establishment in Australia

Malacorhinus irregularis Jacoby (Coleoptera: Chrysomelidae: Galerucinae: Galerucini), from Mexico is identified as a potential biological control agent for Mimosa pigra L. (Mimosaceae), a serious weed of northern Australia and Asia. The adults feed on leaves of the host, and the larvae develop on seedlings, roots, and perhaps other plant parts. The damage to the target plant is substantial, indicating that this insect could be an effective control agent. Host-specificity tests examined the suitability of seedlings and leaves for larval development, and suitability of leaves for adult feeding. In no-choice tests, no larval development occurred on any of the 81 test plant species other than M. pigra. The extent of adult feeding on the test plants was negligible in the tests using a choice-minus-control design, being less than 1% of that which occurred on M. pigra. We conclude that M. irregularis is a specialist on its host and the risk associated with its release in Australia is low. It was released in infestations of M. pigra in the Northern Territory of Australia in 2000. Establishment and abundance was monitored at one site where the number and distribution of adult beetles fluctuated widely as soil moisture conditions varied through the seasons. Adults were found for two years after release and local defoliation of plants was attributed to this species. Although only limited observations were made, adult feeding was not recorded from Neptunia major (Benth). Windler plants growing in close proximity to M. pigra, indicating specificity under field conditions.     

Mimosa pudica: Electrical and mechanical stimulation of plant movements

Thigmonastic movements in the sensitive plant Mimosa pudica L., associated with fast responses to environmental stimuli, appear to be regulated through electrical and chemical signal transductions. The thigmonastic responses of M. pudica can be considered in three stages: stimulus perception, electrical signal transmission and induction of mechanical, hydrodynamical and biochemical responses. We investigated the mechanical movements of the pinnae and petioles in M. pudica induced by the electrical stimulation of a pulvinus, petiole, secondary pulvinus or pinna by a low electrical voltage and charge. The threshold value was 1.3–1.5 V of applied voltage and 2 to 10 µC of charge for the closing of the pinnules. Both voltage and electrical charge are responsible for the electro‐stimulated closing of a leaf. The mechanism behind closing the leaf in M. pudica is discussed. The hydroelastic curvature mechanism closely describes the kinetics of M. pudica leaf movements.     

An invasive Mimosa in India does not adopt the symbionts of its native relatives

Background and Aims

The large monophyletic genus Mimosa comprises approx. 500 species, most of which are native to the New World, with Central Brazil being the main centre of radiation. All Brazilian Mimosa spp. so far examined are nodulated by rhizobia in the betaproteobacterial genus Burkholderia. Approximately 10 Mya, transoceanic dispersal resulted in the Indian subcontinent hosting up to six endemic Mimosa spp. The nodulation ability and rhizobial symbionts of two of these, M. hamata and M. himalayana, both from north-west India, are here examined, and compared with those of M. pudica, an invasive species.

Methods

Nodules were collected from several locations, and examined by light and electron microscopy. Rhizobia isolated from them were characterized in terms of their abilities to nodulate the three Mimosa hosts. The molecular phylogenetic relationships of the rhizobia were determined by analysis of 16S rRNA, nifH and nodA gene sequences.

Key Results

Both native Indian Mimosa spp. nodulated effectively in their respective rhizosphere soils. Based on 16S rRNA, nifH and nodA sequences, their symbionts were identified as belonging to the alphaproteobacterial genus Ensifer, and were closest to the ‘Old World’ Ensifer saheli, E. kostiensis and E. arboris. In contrast, the invasive M. pudica was predominantly nodulated by Betaproteobacteria in the genera Cupriavidus and Burkholderia. All rhizobial strains tested effectively nodulated their original hosts, but the symbionts of the native species could not nodulate M. pudica.

Conclusions

The native Mimosa spp. in India are not nodulated by the Burkholderia symbionts of their South American relatives, but by a unique group of alpha-rhizobial microsymbionts that are closely related to the ‘local’ Old World Ensifer symbionts of other mimosoid legumes in north-west India. They appear not to share symbionts with the invasive M. pudica, symbionts of which are mostly beta-rhizobial.     

Effect of defoliation treatment on Mimosa pigra L. seedling survivability and resilience

Current advancements in the study of the theoretical basis of species interactions are helping scientists understand the basic parameters governing the dynamics of the interactions between generalist herbivores and their target plants. In practice, however, both inter- and intra-specific interactions between plants (as well as between herbivores and plants) within multispecies systems that are under the influence of interrelated biotic and abiotic variables are difficult to predict. Here, we discuss our findings on the effect of simulated herbivory on Mimosa pigra L. leaves on seedling survivability. In Malaysia, M. pigra, a semi-aquatic invasive plant introduced from the South American region, is already creating an ecological problem, especially in wetland habitats. To better understand the impact of herbivores on the M. pigra population, a simulated experiment of the herbivory effect on Mimosa seedlings was conducted. This experiment combined two treatments of simulated herbivory on the leaves of established Mimosa seedlings, that is, a two-level intensity treatment (50 and 100 % defoliation) and a seven-level frequency treatment (one to seven defoliations). The data suggest that Mimosa is highly resilient against herbivory. This plant was able to compensate for repeated losses, thus suggesting that the introduction of herbivores in an effort to totally eradicate the Mimosa population is unlikely to be successful.     

Tubulin from Mimosa pudica and its involvement in leaf movement

The sensitive plant Mimosa pudica is made insensitive by a brief treatment with colchicine. A high concentration of colchicine binding protein is present in the fresh actively moving leaves of M. pudica. This protein was partially characterized and compared with the animal brain tubulin. This colchicine binding activity is very low in the insensitive variety of Mimosa, namely Mimosa rubricaulis.     

Mechanical and electrical anisotropy in Mimosa pudica pulvini

Thigmonastic or seismonastic movements in Mimosa pudica, such as the response to touch, appear to be regulated by electrical, hydrodynamical and chemical signal transduction. The pulvinus of Mimosa pudica shows elastic properties, and we found that electrically or mechanically induced movements of the petiole were accompanied by a change of the pulvinus shape. As the petiole falls, the volume of the lower part of the pulvinus decreases and the volume of the upper part increases due to the redistribution of water between the upper and lower parts of the pulvinus. This hydroelastic process is reversible. During the relaxation of the petiole, the volume of the lower part of the pulvinus increases and the volume of the upper part decreases. Redistribution of ions between the upper and lower parts of a pulvinus causes fast transport of water through aquaporins and causes a fast change in the volume of the motor cells. Here, the biologically closed electrochemical circuits in electrically and mechanically anisotropic pulvini of Mimosa pudica are analyzed using the charged capacitor method for electrostimulation at different voltages. Changing the polarity of electrodes leads to a strong rectification effect in a pulvinus and to different kinetics of a capacitor discharge if the applied initial voltage is 0.5 V or higher. The electrical properties of Mimosa pudica''s pulvini were investigated and the equivalent electrical circuit within the pulvinus was proposed to explain the experimental data. The detailed mechanism of seismonastic movements in Mimosa pudica is discussed.Key words: electrophysiology, plant electrostimulation, pulvinus, Mimosa pudica, charged capacitor method, electrical circuits, ion channels     

Host specificity ofAcanthoscelides quadridentatus andA. Puniceus [Col.: Bruchidae] for biological control ofMimosa pigra (with preliminary data on their biology)

The biology and host specificity of the seed-feeding bruchids,Acanthoscelides quadridentatus (Schaeffer) andA. puniceus Johnson, from Mexico were studied in quarantine facilities in Australia. Distinguishing characters in the genitalia of each species are illustrated. Oviposition was recorded on 16 of 73 species of plants tested but larvae died without entering pods or seeds, except onMimosa invisa K. F. P. von Martius andM. pigra L. Larvae entering seeds ofM. invisa died in the first instar. The bruchids were clearly specific toM. pigra and were subsequently released as part of a program for biological control of this weed in the Northern Territory, Australia in April 1983 and thailand in July 1984.      

Genome sequence of Burkholderia mimosarum strain LMG 23256T,a Mimosa pigra microsymbiont from Anso,Taiwan

Burkholderia mimosarum strain LMG 23256^T is an aerobic, motile, Gram-negative, non-spore-forming rod that can exist as a soil saprophyte or as a legume microsymbiont of Mimosa pigra (giant sensitive plant). LMG 23256^T was isolated from a nodule recovered from the roots of the M. pigra growing in Anso, Taiwan. LMG 23256^T is highly effective at fixing nitrogen with M. pigra. Here we describe the features of B. mimosarum strain LMG 23256^T, together with genome sequence information and its annotation. The 8,410,967 bp high-quality-draft genome is arranged into 268 scaffolds of 270 contigs containing 7,800 protein-coding genes and 85 RNA-only encoding genes, and is one of 100 rhizobial genomes sequenced as part of the DOE Joint Genome Institute 2010 Genomic Encyclopedia for Bacteria and Archaea-Root Nodule Bacteria (GEBA-RNB) project.     

Detection of microcystin producing cyanobacteria in Spirulina dietary supplements using multiplex HRM quantitative PCR

Arthrospira species, under the name ‘Spirulina’, are used as food supplement for its protein, vitamins, and minerals which have several health benefits. Cyanobacterial toxins including microcystins can possibly contaminate these dietary supplements causing hepatotoxicity, tumour formation, and other disorders. The safe use of dietary supplements necessitates the need to assess such toxins in the algal food supplement. The methods which evaluate these dietary supplements should be highly sensitive, cost-effective, and rapid. In this study, multiplex HRM qPCR analysis was used to detect microcystin (MC)-producing cyanobacteria in Spirulina dietary supplements. The multiplex HRM qPCR detection limit was found to be 25 ag of mcyB spiked in a standard concentration of pcb (25 pg). Two distinct melt curves characteristic of pcb (Tm 82.8 ± 0.07 °C) and mcyB (Tm 77.9 ± 0.05 °C) were observed. Microcystin contamination was detected only in the fish food supplements and not in human dietary supplements of Spirulina. Liquid chromatography–high-resolution mass spectrometry analysis further confirmed the presence of the congeners of microcystin in the identified positive samples.     

Improved screening of microcystin genes and toxins in blue-green algal dietary supplements with PCR and a surface plasmon resonance biosensor

Microcystins (MCs) comprise a group of cyclic heptapeptide toxins that share a common backbone and have two variable l-amino acids that yield at least 21 known analogs of varying potency. These hepatotoxins and potential tumor promoters are produced by certain cyanobacteria, including Microcystis aeruginosa. The cyanobacterium M. aeruginosa blooms in freshwater lakes and can potentially co-occur with other species such as Aphanizomenon flos-aquae, which is targeted and harvested for the production of dietary supplements known as blue-green algae (BGA). BGA supplements are currently marketed in the U.S. and internationally as a product that may elevate mood, increase energy, and alleviate attention deficit hyperactivity disorder. However, the potential for BGA dietary supplements to be contaminated with MCs is of concern, and there are currently no validated methods for detection of MCs in these products. This research focused on establishing screening methods for toxic Microcystis and MCs in BGA supplements. A DNA-based method employing polymerase chain reaction (PCR) was used as a prescreening tool to evaluate the dietary supplements and to detect the presence of toxin genes (i.e., presence of toxic Microcystis). A rapid, sensitive surface plasmon resonance (SPR) biosensor, directed towards recognition of all MC forms, was also developed and validated. This improved SPR biosensor incorporates a commercial Adda-group antibody (Ab) that has the capacity for broader recognition of MCs than previously developed sensors for BGA supplements that rely solely on an arginine-reactive Ab and can quantitate MC levels down to 0.24 ng/mL (equivalent to 0.24 μg per gram of BGA supplement) in less than 10 min. Such a rapid, quantitative screening method may allow for further surveillance of BGA products to assist risk assessment efforts, establishment of regulatory guidance levels, and response to potential consumer complaints related to BGA products. The PCR technique and SPR biosensor may be used in concert as prescreening and screening tools, respectively or individually, thereby limiting the number of samples that must be evaluated with confirmatory methods.     

Guaiane type sesquiterpenes and other constituents from Daucus carota L.

In a chemosystematic investigation of the fruits of Daucus carota L. we have isolated eleven compounds including four guaiane type sesquiterpenes (1–4), one eudesmane type sesquiterpene (5) and six other constituents (6–11). Among them, the five compounds 1–5 all are new for Daucus carota L. and all have been reported in Torilis japonica. The results show that Daucus carota L. is chemically similar with Torilis japonica providing chemical evidence for both species used as the same traditional Chinese medicine “nanheshi”.     

IAA-induced hyperpolarization of the membrane potential in isolated cells fromMimosa pulvinus

Upon treatment with 10⁻⁴ M IAA the membrane potential of an isolated cell from the main pulvinus, ofMimosa pudica L. depolarized by about 6 mV in 2–5 min, but later it gradually hyperpolarized by about 30 mV. The membrane potential of a motor cell in the main pulvinar tissue hyperpolarized by about 80 mV 1 hr after application of 10⁻⁴ M IAA.     

Morphing structures and signal transduction in Mimosa pudica L. induced by localized thermal stress

Leaf movements in Mimosa pudica, are in response to thermal stress, touch, and light or darkness, appear to be regulated by electrical, hydrodynamical, and chemical signal transduction. The pulvinus of the M. pudica shows elastic properties. We have found that the movements of the petiole, or pinnules, are accompanied by a change of the pulvinus morphing structures. After brief flaming of a pinna, the volume of the lower part of the pulvinus decreases and the volume of the upper part increases due to the redistribution of electrolytes between these parts of the pulvinus; as a result of these changes the petiole falls. During the relaxation of the petiole, the process goes in the opposite direction. Ion and water channel blockers, uncouplers as well as anesthetic agents diethyl ether or chloroform decrease the speed of alert wave propagation along the plant. Brief flaming of a pinna induces bidirectional propagation of electrical signal in pulvini. Transduction of electrical signals along a pulvinus induces generation of an action potential in perpendicular direction between extensor and flexor sides of a pulvinus. Inhibition of signal transduction and mechanical responses in M. pudica by volatile anesthetic agents chloroform or by blockers of voltage gated ion channels shows that the generation and propagation of electrical signals is a primary effect responsible for turgor change and propagation of an excitation. There is an electrical coupling in a pulvinus similar to the electrical synapse in the animal nerves.     

Melissopalynological analysis of stingless bee (Tetragonula pagdeni) honey in Eastern Thailand

Melissopalynological analysis of 72 Tetragonula pagdeni honey samples, collected from various locations in Chanthaburi (A) and Trat (B) provinces, Eastern Thailand during March 2015, was performed. Overall, 45 pollen types species belonging to 22 plant families were identified. The predominant pollen type was from Nephelium lappaceum and comprised 48.5% of the pollen in honey from location A2 (Pathavee district) and 45.3% in location B1 (AoYai district). The secondary pollen types, Wodyetia bifurcata and Mimosa pudica, accounted for 20.1% and 17.0%, respectively, in location B3 (Nhongsamed district), while Cocos nucifera accounted for 17.2% in location A2. In addition, pollen types of C. nucifera, M. pudica, N. lappaceum, Asystasia gangetica, Amaranthus lividus, Areca catechu, Chromolaena odorata and Durio zibethinus were found in T. pagdeni honey from all sampled locations. Furthermore, in the dearth period, T. pagdeni foraged food (as in pollen was present) from Musa sp., Acacia mangium and various weed species, such as A. gangetica, A. lividus, Ageratum conyzoides, Bidens pilosa, C. odorata, Melampodium divaricatum, Mikania cordata, Merremia umbellata, M. pudica, Pennisetum pedicellarum and Thysanoleana maxima, from within a 500?m radius around the hive to maintain their colonies.     

The enzyme involved in sulfation of the turgorin, gallic acid 4-O-(β-d-glucopyranosyl-6'-sulfate) is pulvini-localized in Mimosa pudica

A sulfotransferase (ST) which catalyzes the transfer of sulfate from 3′-phosphoadenosine 5′-phosphosulfate (PAPS) to gallic acid glucoside was characterized from microsomal preparations of Mimosa pudica. The product of the reaction was found to co-elute on HPLC with the periodic leaf movement factor 1 (PLMF-1) (gallic acid β-d -gluco-pyranosyl-6′-sulfate). The distribution of the enzyme activity was restricted to plasma membrane preparations from primary, secondary and tertiary pulvini. The M. pudica ST activity was inhibited in a dose-dependent manner in the presence of an antibody raised against the flavonol 3-sulfotransferase of Flaveria chloraefolia, suggesting structural similarities between the two proteins. Western blot analysis of M. pudica protein extracts using these antibodies indicated the presence of a cross-reactive polypeptide with an apparent molecular mass of 42 000 Da whose distribution correlates with the presence of the gallic acid glucoside ST activity. Indirect immunogold labeling of resin-embedded sections from tertiary pulvini showed a specific localization of gold particles on the sieve-tube plasma membranes. The label distribution was uniform and other cellular organelles and membrane systems displayed little or no labeling. The results of the Western blot and immunocytochemical studies are consistent with the detection of the gallic acid glucoside ST activity in plasma membrane preparations of M. pudica pulvini cells. The specific tissue distribution of the ST in motor organ phloem cells suggests that this is the site of synthesis and/or accumulation of PLMF-1 and supports the proposed hypothesis that PLMF-1 may be acting as a chemical signal during the seismonastic response of M. pudica.     

Cytotoxic activity of acetogenins and styryl lactones isolated from Goniothalamus undulatus Ridl. root extracts against a lung cancer cell line (COR-L23)

An investigation of the chemical constituents in a dichloromethnae extract of Goniothalamus undulatus root led to the isolation of three known styryl lactones (5-acetoxyisogoniothalamin oxide, O-acetylaltholactone and altholactone), and four known annonaceous acetogenins (annonacin, cis-annonacin, goniothalamicin and cis-goniothalamicin). These compounds were subjected to a sulphorhodamine B (SRB) cytotoxicity assay against human large cell lung carcinoma (COR-L23), and normal human fetal fibroblast (MRC-5), cell lines. The isolated acetogenins showed higher cytotoxic activity against COR-L23 compared to the styryl lactones, with IC₅₀ values in the range of 0.5-1.7 μM and 7.4-15.4 μM, respectively. A similar pattern of cytotoxicity was also observed against the other cell line (MRC-5); acetogenins IC₅₀ values were in the range of 11.8-31.4 μM, and those for styryl lactones were in the range of 48.7-102.8 μM. This is the first report of a bioassay-guided isolation of chemical constituents from G. undulatus and on cytotoxic studies of the isolated compounds using these particular lung cancer cell lines.