Sensilla coeloconica ringed by microtrichia in host‐seeking biting midges

The distribution and morphology of antennal sensilla coeloconica in parasitic and predaceous biting midges were studied in females of Forcipomyia (feeding on the blood of frogs), Atrichopogon (feeding on haemolymph), Austroconops, Culicoides (feeding on the blood of birds and mammals) and Brachypogon (feeding on haemolymph and dissolved tissues of insects) (all: Diptera: Ceratopogonidae). A Lower Cretaceous female of Archiculicoides (Diptera: Ceratopogonidae) from Lebanese amber, which fed on the blood of unknown vertebrates, was also examined. In sensilla coeloconica ringed by microtrichia, the peg is grooved longitudinally and protrudes distinctly from the pit. We suggest that the microtrichia encircling the protruding peg form a structure resembling a picket fence in order to maintain a higher level of humidity, which facilitates the capture and transport of odour molecules through the channels in the peg wall. Sensilla coeloconica ringed by microtrichia function as very effective chemoreceptors in host‐ and prey‐seeking activity. During the evolution of Ceratopogonidae, sensilla coeloconica with a fence of microtrichia have evolved twice in groups feeding on the blood of vertebrates (i.e. in the basal lineage: Lower Cretaceous or earlier) and in the subgenus Lasiohelea of Forcipomyia (Palaeogene). Sensilla coeloconica ringed by microtrichia are described for the first time in the relict genus Austroconops.     

Passive recovery of an island bird community after rodent eradication

The number and scale of island invasive species eradications is growing, but quantitative evidence of the conservation efficacy of passive recovery is limited. We compare relative abundances of breeding birds on Hawadax Island (formerly named Rat island), Aleutian Archipelago, Alaska, pre- and post- rat eradication to examine short-term (<1 year post-eradication) changes due to rodenticide application, and medium-term (5 years post-eradication) changes due to the absence of invasive rats. In the short term, Bald Eagle (Haliaeetus leucocephalus) numbers decreased from 24 individuals pre-eradication to two individuals <1 year post-eradication, but recovered to 10 individuals (42 % of pre-eradication) 5 years post-eradication, with all individuals nesting (63 % of the pre-eradication nesting). Five years post-eradication relative abundances of most terrestrial birds surveyed using point counts either significantly increased [Gray-crowned Rosy Finch (Leucosticte tephrocotis), Lapland Longspur (Calcarius lapponicus), Snow Bunting (Plectrophenax nivalis), Song Sparrow (Melospiza melodia)] or did not differ [Pacific Wren (Troglodytes troglodytes)]. Shorebirds also increased 5 years post-eradication with Black Oystercatchers (Haematopus palliates) increasing fivefold, and Rock Sandpiper (Calidris ptilocnemis) nesting increasing from one to five nests. We confirmed two species of ground nesting seabirds [Tufted Puffin (Fratercula cirrhata) and Leach’s Storm-petrel (Oceanodroma leucohoa)] as nesting (puffin) or engaged in courtship behavior (Storm-petrel) 5 years post-eradication. Our results indicate that despite the short-term impact on Bald Eagles, and without further human intervention, most terrestrial and marine birds have newly-colonized, re-colonized, or increased in abundance following the eradication of invasive rats.     

Intracellular polyamine biosynthesis is required for interleukin 2 responsiveness during lymphocyte mitogenesis

The objective of the present investigation was to define a more precise role for intracellular polyamine biosynthesis with respect to specific inducible events which regulate lymphocyte mitogenesis. In this regard, we have examined the effect of polyamine depletion on interleukin 2 (IL-2) production, receptor expression, and responsiveness in Con A stimulated mononuclear leukocytes (MNL). Polyamine depletion was achieved utilizing the specific irreversible inhibitor of ornithine decarboxylase (ODC), DL-alpha-difluoromethylornithine (DFMO). Polyamine depletion of MNL augmented detectable levels of Con A-induced IL-2 activity. In contrast, the ability of polyamine depleted MNL to respond to saturating levels of IL-2 (100 U/ml) following 72 or 96 hr of Con A stimulation was reduced 100 and 81%, respectively. Nonetheless, polyamine depletion did not impair the induction of IL-2 receptor expression. High-affinity IL-2 receptor density in the polyamine depleted population was greater than control cells late in culture (96 hr). The expression of high-affinity IL-2 receptors did not correlate with an ability to respond to IL-2 in the polyamine depleted population. The results of this study demonstrate for the first time that intracellular polyamine biosynthesis is required for IL-2 responsiveness during a primary mitogenic lymphocyte response.     

Concordant phylogeography and cryptic speciation in two Western Palaearctic oak gall parasitoid species complexes

Little is known about the evolutionary history of most complex multi‐trophic insect communities. Widespread species from different trophic levels might evolve in parallel, showing similar spatial patterns and either congruent temporal patterns (Contemporary Host‐tracking) or later divergence in higher trophic levels (Delayed Host‐tracking). Alternatively, host shifts by natural enemies among communities centred on different host resources could disrupt any common community phylogeographic pattern. We examined these alternative models using two Megastigmus parasitoid morphospecies associated with oak cynipid galls sampled throughout their Western Palaearctic distributions. Based on existing host cynipid data, a parallel evolution model predicts that eastern regions of the Western Palaearctic should contain ancestral populations with range expansions across Europe about 1.6 million years ago and deeper species‐level divergence at both 8–9 and 4–5 million years ago. Sequence data from mitochondrial cytochrome b and multiple nuclear genes showed similar phylogenetic patterns and revealed cryptic genetic species within both morphospecies, indicating greater diversity in these communities than previously thought. Phylogeographic divergence was apparent in most cryptic species between relatively stable, diverse, putatively ancestral populations in Asia Minor and the Middle East, and genetically depauperate, rapidly expanding populations in Europe, paralleling patterns in host gallwasp species. Mitochondrial and nuclear data also suggested that Europe may have been colonized multiple times from eastern source populations since the late Miocene. Temporal patterns of lineage divergence were congruent within and across trophic levels, supporting the Contemporary Host‐tracking Hypothesis for community evolution.     

Effects of citronella oil (Cymbopogon winterianus Jowitt ex Bor) on Spodoptera frugiperda (J. E. Smith) midgut and fat body

The armyworm, Spodoptera frugiperda, is the principal pest of corn in Brazil. Control is achieved primarily by synthetic insecticides, which cause problems for the agro-ecosystem. Alternative methods of control are under investigation and citronella (Cymbopogon winterianus) essential oil appears to be a promising agent. We investigated the effects of citronella oil using histological, histochemical and immunohistochemical methods. The midgut of larvae treated with citronella exhibited altered epithelium including cytoplasmic protrusions, columnar cell extrusion, pyknotic nuclei, and increased periodic acid-Schiff positive granules. Regenerative cells in the epithelium of the midgut increased in number, which facilitated subsequent regeneration of this tissue. After exposure to citronella, trophocytes, the principal cell type of the fat body, possessed enlarged vacuoles and mitotic bodies, and contained reduced amounts of glycogen, lipid, and protein. Citronella oil caused morphological changes of the midgut and reduction of stored resources in the fat body, which may adversely affect insect reproduction and survival.     

Restricted epithelial proliferation by lacritin via PKCalpha-dependent NFAT and mTOR pathways

Renewal of nongermative epithelia is poorly understood. The novel mitogen "lacritin" is apically secreted by several nongermative epithelia. We tested 17 different cell types and discovered that lacritin is preferentially mitogenic or prosecretory for those types that normally contact lacritin during its glandular outward flow. Mitogenesis is dependent on lacritin's C-terminal domain, which can form an alpha-helix with a hydrophobic face, as per VEGF's and PTHLP's respective dimerization or receptor-binding domain. Lacritin targets downstream NFATC1 and mTOR. The use of inhibitors or siRNA suggests that lacritin mitogenic signaling involves Galpha(i) or Galpha(o)-PKCalpha-PLC-Ca2+-calcineurin-NFATC1 and Galpha(i) or Galpha(o)-PKCalpha-PLC-phospholipase D (PLD)-mTOR in a bell-shaped, dose-dependent manner requiring the Ca2+ sensor STIM1, but not TRPC1. This pathway suggests the placement of transiently dephosphorylated and perinuclear Golgi-translocated PKCalpha upstream of both Ca2+ mobilization and PLD activation in a complex with PLCgamma2. Outward flow of lacritin from secretory cells through ducts may generate a proliferative/secretory field as a different unit of cellular renewal in nongermative epithelia where luminal structures predominate.     

Impacts of bud set and lammas phenology on root:shoot biomass partitioning and carbon gain physiology in poplar

Key message

Timing of bud set and occurrence of lammas in trees can alter growth partitioning (i.e., root:shoot ratios), while only bud set effectively modifies carbon gain by increasing photosynthesis-related physiological traits.

Abstract

Bud set and lammas (second bud flushing) phenology may strongly influence growth, physiology, and biomass in trees. To test effects of these phenological events, 54 individuals from 16 genotypes of black cottonwood poplar (Populus trichocarpa) were grown in a potted trial under greenhouse conditions (with extended daylengths promoting growth), followed by open-air cultivation (with natural daylengths promoting bud set and/or lammas). Trees were monitored for phenology, repeatedly measured for photosynthesis-related traits, harvested for biomass, and assessed for growth partitioning (separating above- and belowground parts). We grouped trees by phenology for comparisons: (1) trees with early summer bud set, (2) trees with early summer bud set that underwent lammas, (3) trees with late summer bud set (August), and (4) trees with bud set occurring in autumn (September). We found that bud set timing positively affected growth partitioning where earlier bud set resulted in shorter trees with higher root:shoot biomass ratios (by increasing root mass). Lammas growth altered these ratios by significantly increasing shoot growth relative to belowground growth. Trees with bud set occurring in late summer also had higher root:shoot biomass ratios (by increasing root mass) compared to trees setting bud in autumn. Occurrence of bud set coincided with modified physiology of the existing canopy where photosynthesis-related traits were enhanced relative to trees still actively growing. These physiological changes were unaltered by occurrence of lammas. This suggests that bud set prompts a significant, coordinated mechanism of higher carbon gain physiology and belowground biomass accumulation in plants within a “post-bud set” phase.

     

Purification of TnsB, a transposition protein that binds to the ends of Tn7.

We have purified TnsB, a transposition protein encoded by the bacterial transposon Tn7. The purification procedure involves three chromatographic steps (DNA-cellulose, norleucine-Sepharose, and phosphocellulose) and yields milligram quantities of highly purified protein. The apparent molecular mass of denatured TnsB protein is approximately 85 kDa. Gel filtration chromatography and sucrose gradient sedimentation studies indicate that in solution, native TnsB is a monomer of nonspherical shape. Using DNase I protection analysis, we established that TnsB is a sequence-specific DNA-binding protein that recognizes multiple sites in both ends of the transposon. The TnsB binding sites, three in the left end of Tn7 and four in the right end, are highly related in nucleotide sequence and are located in DNA segments that we have previously shown contain cis-acting sequences important for Tn7 transposition. Our results also show that one of the TnsB binding sites overlaps a proposed promoter for the transposition genes of Tn7. These studies suggest that the specific binding of TnsB to the ends of Tn7 mediates recombination and may also regulate the expression of Tn7-encoded transposition genes.