Hanging by a thread: Post-attack defense of caterpillars

Caterpillars use a diverse range of anti-predator defenses, including camouflage, making and hiding in shelters, mimicry, regurgitating, rolling, and biting. Some caterpillars also drop to the ground and hang themselves by a silk thread. This hanging behavior has been described for a long time but has surprisingly been overlooked in entomological research. In this study, we aimed to identify (1) the taxonomic distribution of the species showing the hanging behavior and (2) the type of sensory stimulus that induces the hanging behavior. We first located caterpillars in the forest and stimulated each caterpillar with three different types of sensory stimuli sequentially: visual approaching, wind-blowing, and poking. For those who responded to none of the stimuli, we further delivered harder tactile stimuli (pinching and detaching from the plants by grabbing) and observed whether they performed the hanging behavior. Among the surveyed 88 species, 46 species (comprising 11 different families) were confirmed to perform the hanging behavior. Most species responded to neither visual nor wind stimulus, but about half of the tested individuals responded to one of the tactile stimuli. Our results suggest that hanging by a silk thread is widespread across a range of lepidopteran groups, and they use this behavior as a post-attack defense.     

Untangling the Tangle-Web: Web Construction Behavior of the Comb-Footed Spider Steatoda triangulosa and Comments on Phylogenetic Implications (Araneae: Theridiidae)

Theridiidae typically construct a three-dimensional web often described as irregular. The web consists of a supporting structure and lines under tension termed gumfooted lines. We used automated methods to observe web construction in the theridiid Steatoda triangulosa under laboratory conditions. Web construction lasted several nights. After orientation, spiders built a three-dimensional structure of several threads radiating sideways and downward from the retreat. To build gumfooted lines, they started from the retreat, moved along a structural thread, then dropped down to attach the thread to the lower substrate. On returning, they coated the lowest part of the thread with viscid silk before moving up along the same thread back to the structural thread. They then continued moving along the same structural thread to drop down again to build the next gumfooted line. This behavior was continued until the spiders had built a series of gumfooted lines (a bout). There were regular intervals between the construction of two bouts. Thus, a single web included many bouts built in different stages. We show that gumfooted lines are not homologues to sticky web elements of orb-weavers and present new synapomorphic characters that support the monophyly of Theridiidae + Nesticidae and the monophyly of araneoid sheet web weavers. Further, the time allocation pattern for different behavioral stages and the fine structure of a gumfooted line are presented.     

Genetic and functional analysis of the nodulation region of the Rhizobium leguminosarum Sym plasmid pRL1JI

Thirty Tn5- or Tn1831-induced nodulation (nod) mutants of Rhizobium leguminosarum were examined for their genetic and symbiotic properties. Thirteen mutants contained a deletion in Sym plasmid pRL1JI. These deletions cover the whole nod region and are 50 kb in size. All remaining seventeen mutations are located in a 6.6 kb EcoRI nod fragment of the Sym plasmid. Mutations in a 3.5 kb part on the right hand side of this 6.6 kb fragment completely prevent nodulation on Vicia sativa. All mutants in this 3.5 kb area are unable to induce marked root hair curling and thick and short roots.Mutations in a 1.5 kb area on the left hand side of the 6.6 kb nod fragment generate other symbiotic defects in that nodules are only rarely formed and only so after a delay of several days. Moreover, infection thread formation is delayed and root hair curling is more excessive than that caused by the parental strain. Their ability to induce thick and short roots is unaltered.Mutations in this 1.5 kb region are not complemented by pRmSL26, which carries nod genes of R. meliloti, whereas mutations in the 3.5 kb region are all complemented by pRmSL26.Abbreviations Rps repression of production of small bacteriocin - Mep medium bacteriocin production - Nod nodulation - Fix fixation - Tsr thick and short roots - Flac root hair curling - Hsp host specificity - Flad root hair deformation - Tc tetracycline - Km kanamycin - Cm chloramphenicol - Sp spectinomycin - Sm streptomycin - R resistant     

Ultrastructure of infection-thread development during the infection of soybean by Rhizobium japonicum

The location and topography of infection sites in soybean (Glycine max (L.) Merr.) root hairs spot-inoculated with Rhizobium japonicum have been studied at the ultrastructural level. Infections commonly developed at sites created when the induced deformation of an emerging root hair caused a portion of the root-hair cell wall to press against an adjacent epidermal cell, entrapping rhizobia within the pocket between the two host cells. Infections were initiated by bacteria which became embedded in the mucigel in the enclosed groove. Infection-thread formation in soybean appears to involve degradation of mucigel material and localized disruption of the outer layer of the folded hair cell wall by one or more entrapped rhizobia. Rhizobia at the site of penetration are separated from the host cytoplasm by the host plasmalemma and by a layer of wall material that appears similar or identical to the normal inner layer of the hair cell wall. Proliferation of the bacteria results in an irregular, wall-bound sac near the site of penetration. Tubular infection threads, bounded by wall material of the same appearance as that surrounding the sac, emerge from the sac to carry rhizobia roughly single-file into the hair cell. Growing regions of the infection sac or thread are surrounded by host cytoplasm with high concentrations of organelles associated with synthesis and deposition of membrane and cell-wall material. The threads follow a highly irregular path toward the base of the hair cell. Threads commonly run along the base of the hair cell for some distance, and may branch and penetrate into subjacent cortical cells at several points in a manner analagous to the initial penetration of the root hair.     

厚壳贻贝Mytilus coruscus足丝盘及足丝的多巴分析

多巴(3,4-1-dihydroxyphenylalanine,DOPA)是贻贝足丝粘附蛋白中的一种特殊的氨基酸,由酪氨酸经羟化后生成,与贻贝足丝粘附蛋白的强粘附性能具有直接联系.目前,已鉴定的多种贻贝足丝蛋白序列中均发现有不同含量的DOPA存在.蛋白中DOPA的定量检测对于了解DOPA在蛋白粘附中的作用以及粘附蛋白的...     

Plasmolysis of Pteridium protoplasts: A study using light and scanning-electron microscopy

A study was undertaken using gametophytes of the fern Pteridium aquilinum to examine the effects of plasmolysis on the topography of protoplasts. Methods are described whereby the surfaces of non-isolated protoplasts can be observed in the plasmolysed condition using scanning electron microscopy. Plasmolysed gametophytes were also examined in the light microscope using differential interference contrast and ultra-violet fluorescence microscopy after staining with fluorescein diacetate. With scanning electron microscopy, plasmolysed protoplast surfaces appeared smooth with no evidence of wrinkling or infolding of excess membrane. The formation of irregular-shaped protoplasts, protoplasmic threads, subprotoplasts, and protoplasmic networks covering internal wall surfaces all provided evidence for strong wall adhesion of the protoplasm. The availability of membrane for uptake into folds or vesicles is therefore thought to be minimal. Transmission electron microscopy showed some protoplasmic threads to be plasmodesmata, the remainder being cell-wall contact points. Remnants of these threads were occasionally observed on isolated protoplasts in both the light and electron microscopes.     

Reinforced bioartificial dermis constructed with collagen threads

In this work, a novel type of composite scaffold was designed, which has the suitability of both high biocompatibility and strong mechanical properties, for use in bioartificial dermis applications. The reinforced scaffold consisted of a lyophilized collagen sponge formed around a cross-linked collagen meshwork with an average thread diameter of approximately 55 μm. Fibroblasts were cultured in the reinforced collagen sponge for 7 days, during which time the pores in the sponge became filled with cells that secreted extracellular matrix (ECM) to form a bioartificial dermis. Results of ultimate tensile strength (UTS) measurements and compression tests indicated that the bioartificial dermis formed around the reinforced collagen sponge showed about ten times the strength of the bioartificial dermis formed around a typical collagen sponge (1.5 ± 0.05 vs. 0.15 ± 0.05 and 2.5 ± 0.1 vs. 0.2 ± 0.08 MPa, respectively). As a result, reinforced collagen mesh improved mechanical properties and this technique will be possible to make stronger scaffolds, not only for artificial skin applications but also various artificial tissues, such as synthetic cartilage, bone, and blood vessels.     

基于illumina测序的厚壳贻贝足组织转录组研究

贻贝足丝是贻贝足组织分泌的足丝蛋白形成的非细胞组织,具有在水环境下的极强粘附性能,是当前生物粘附剂及抗腐蚀材料的研发热点．为进一步了解贻贝足丝蛋白的分子多样性特征,采用新一代Illumina高通量测序平台对厚壳贻贝(Mytilus coruscus)足组织进行转录组测序,首次构建了厚壳贻贝足组织的转录组数据库．共计获得7 199 799 840 nt的碱基数据经过序列拼接和组装,获得88 825条unigene．对上述unigene开展了序列注释,共计37 007条unigene获得注释．在此基础上,经序列检索和比对,从中筛选出与目前已知的11种足丝蛋白同源的56条unigene序列并进行分析．结果表明,厚壳贻贝足丝蛋白具有明显的氨基酸偏好性,部分足丝蛋白具有重复序列,且厚壳贻贝足丝蛋白与其他种类的贻贝足丝蛋白具有较高的序列相似性．上述结果为后续贻贝足丝蛋白的批量鉴定以及在此基础上的贻贝足丝形成、固化以及粘附机制相关研究奠定了基础．     

PML2‐mediated thread‐like nuclear bodies mark late senescence in Hutchinson–Gilford progeria syndrome

Progerin accumulation disrupts nuclear lamina integrity and causes nuclear structure abnormalities, leading to premature aging, that is, Hutchinson–Gilford progeria syndrome (HGPS). The roles of nuclear subcompartments, such as PML nuclear bodies (PML NBs), in HGPS pathogenesis, are unclear. Here, we show that classical dot‐like PML NBs are reorganized into thread‐like structures in HGPS patient fibroblasts and their presence is associated with late stage of senescence. By co‐immunoprecipitation analysis, we show that farnesylated Progerin interacts with human PML2, which accounts for the formation of thread‐like PML NBs. Specifically, human PML2 but not PML1 overexpression in HGPS cells promotes PML thread development and accelerates senescence. Further immunofluorescence microscopy, immuno‐TRAP, and deep sequencing data suggest that these irregular PML NBs might promote senescence by perturbing NB‐associated DNA repair and gene expression in HGPS cells. These data identify irregular structures of PML NBs in senescent HGPS cells and support that the thread‐like PML NBs might be a novel, morphological, and functional biomarker of late senescence.     

Rhizobium induces marked root hair curling by redirection of tip growth: a computer simulation

Computer simulation shows that Rhizobium can induce marked curling in legume root hairs by growth induction. Essential elements are: a) the attachment of one inducing principle (e.g. one bacterium or a group of bacteria), preferably within the growth area of the root hair; b) translocation of the inductor along the growing root hari tip; and c) redirection of the original plant-driven tip growth. Also other root hair deformations, for example root hair branching and infection thread growth, can be explained with the proposed model.