Relation between temporal persistence of host plants and wing length in leafhoppers (Hemiptera: Auchenorrhyncha)

Abstract.

• 1 Wing form frequencies in 255 populations of 101 species of leafhoppers (Auchenorrhyncha) in temporary and permanent habitats were documented.
• 2 The proportion of brachypterous specimens in the leafhopper assemblages on ruderal host plants in temporary habitats (median 2%, range 0–8%) was significantly lower than that on permanent host plants in undisturbed habitats (median 22%, range 0–94%).
• 3 Leafhopper species typical of temporary habitats were either monomorphic, macropterous, or wing-dimorphic with macropterous forms prevailing in both sexes.
• 4 Among the eighty-nine species recorded in permanent habitats, forty-five species were wing dimorphic. In forty-one dimorphic species, a brachypterous form prevailed. This prevalence was found for both sexes in thirty-one species, for only females in nine species and for only males in one species.
• 5 The prevalence of brachypters in males, but not in females, found in Anoscopus flavostriatus, is probably the first such documented case in Auchenorrhyncha.
• 6 The hypothesis is proposed that in temporary habitats, density-dependent production of macropters in wing dimorphic species is an adaptation to frequent habitat deterioration caused by factors independent of the density of the species.
• 7 The predominance of brachypters in permanent habitats indicates that a density-dependent decrease in fitness usually does not offset the potential decrease in fitness connected with macroptery and dispersal. Because of this inability of leafhopper populations to decrease significantly the quality of their resources, a high population density cannot be used as a predictor of future quality of these resources, which is information essential for efficient dispersal behaviour.

     

Infection process and the interaction of rice roots with rhizobia

Most rhizobial strains inhibit rice root growth in the presence of calcium or potassium nitrates, but not ammonium nitrate. Certain rhizobial strains, however, such as strain R4, do not inhibit rice growth and can enter rice roots and multiply in the intercellular spaces. By using the green fluorescent protein (GFP) as a visual marker, it was found that Rhizobium became intimately associated with rice seedling roots within 24-48 h. During this initial period it was observed that strain R4 could cause structural changes resembling infection threads within the rice root hairs. Generally, the sites of the emerging lateral roots provide a temporary entry point for rhizobia, either by root hair entry or crack entry. All tested GFP-labelled Rhizobium strains infected the root hairs near the base of growing lateral roots. This study suggests that some strains may have the ability to infect rice root tissues via root hairs located at the emerging lateral roots and to spread extensively throughout the rice root.     

Structure of the unusual explosive fruits of the early diverging angiosperm Illicium (Schisandraceae s.l., Austrobaileyales)

All Illicium spp. have explosive fruits, which is a unique character among the basal grade of angiosperms. Illicium fruits consist of several ventrally dehiscing follicles developing from conduplicate carpels, with a prominent, slightly postgenitally fused ventral slit. The closure of the ventral slit is also secured by two mirror‐symmetrical massive longitudinal sclerenchymatous bands in the mesocarp along the edges and by turgor pressure. The pericarp differentiates into a fleshy (or coriaceous) peripheral zone (exocarp and mesocarp) with numerous ethereal‐oil‐containing cells and a sclerenchymatous (single‐layered, palisade) inner zone (endocarp). Dehydration of the fleshy zone of the pericarp and partial compression of the epidermal sclereids with U‐shaped wall thickenings lining the ventral suture are instrumental in explosive fruitlet dehiscence. Generally, the fruit structure of Illicium differs dramatically from those in other early diverging angiosperms. Gynoecium and fruit structure (and a probable early Cretaceous divergence from the Schisandra‐Kadsura clade) provide evidence for treatment of Illicium as separate from Schisandraceae s.s. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013 , 171 , 640–654.     

Effect of sub-optimal root zone temperatures at varied nutrient supply and shoot meristem temperature on growth and nutrient concentrations in maize seedlings (Zea mays L.)

Maize seedlings were grown for 10 to 20 days in either nutrient solution or in soils with or without fertilizer supply. Air temperature was kept uniform for all treatments, while root zone temperature (RZT) was varied between 12 and 24°C. In some treatments the basal part of the shoot (with apical shoot meristem and zone of leaf elongation) was lifted up to separate the indirect effects of root zone temperature on shoot growth from the direct effects of temperature on the shoot meristem.Shoot and root growth were decreased by low RZT to a similar extent irrespective of the growth medium (i.e. nutrient solution, fertilized or unfertilized soil). In all culture media Ca concentration was similar or even higher in plants grown at 12 as compared to 24°. At lower RZT concentrations of N, P and K in the shoot dry matter decreased in unfertilized soil, whereas in nutrient solution and fertilized soil only the K concentration decreased.When direct temperature effects on the shoot meristem were reduced by lifting the basal part of the shoot above the temperature-controlled root zone, shoot growth at low RZT was significantly increased in nutrient solution and fertilized soil, but not in unfertilized soil. In fertilized soil and nutrient solution at low RZT the uptake of K increased to a similar extent as plant growth, and thus shoot K concentration was not reduced by increasing shoot growth rates. In contrast, uptake of N and P was not increased, resulting in significantly decreased shoot concentrations.It is concluded that shoot growth at suboptimal RZT was limited both by a direct temperature effect on shoot activity and by a reduced nutrient supply through the roots. Nutrient concentrations in the shoot tissue at low RZT were not only influenced by availability in the substrate and dilution by growth, but also by the internal demand for growth.     

Plasmid-associated genes in the model micro-symbiont Sinorhizobium meliloti 1021 affect the growth and development of young rice seedlings

Sinorhizobium meliloti strain 1021 and its closely related strain Rm2011 inhibit rice seedling (Oryza sativa L. cv. Pelde) growth and development under certain rice-growing conditions. Experiments showed that inoculation of seedlings with approximately less than 10 cells of 1021 was sufficient to cause this inhibition. By using a series of plasmid-cured and plasmid-deleted derivatives of Rm2011, it was found that interactions between genes encoded on pSymA, and possibly pSymB, of Rm2011, affected rice growth and development by affecting both/either the plant and/or the bacteria. Further studies found that genes potentially related to indole-3-acetic acid (IAA) synthesis and nitrate metabolism, encoded on pSymA, were involved in rice growth inhibition in Sm1021- and Sm2011-treated rice seedlings. We conclude that the rice growth inhibition by S. meliloti Sm1021 is pSymA-associated and is induced by environmental nitrate.     

C-Jun N-terminal kinase controls TDP-43 accumulation in stress granules induced by oxidative stress

Background

TDP-43 proteinopathies are characterized by loss of nuclear TDP-43 expression and formation of C-terminal TDP-43 fragmentation and accumulation in the cytoplasm. Recent studies have shown that TDP-43 can accumulate in RNA stress granules (SGs) in response to cell stresses and this could be associated with subsequent formation of TDP-43 ubiquinated protein aggregates. However, the initial mechanisms controlling endogenous TDP-43 accumulation in SGs during chronic disease are not understood. In this study we investigated the mechanism of TDP-43 processing and accumulation in SGs in SH-SY5Y neuronal-like cells exposed to chronic oxidative stress. Cell cultures were treated overnight with the mitochondrial inhibitor paraquat and examined for TDP-43 and SG processing.

Results

We found that mild stress induced by paraquat led to formation of TDP-43 and HuR-positive SGs, a proportion of which were ubiquitinated. The co-localization of TDP-43 with SGs could be fully prevented by inhibition of c-Jun N-terminal kinase (JNK). JNK inhibition did not prevent formation of HuR-positive SGs and did not prevent diffuse TDP-43 accumulation in the cytosol. In contrast, ERK or p38 inhibition prevented formation of both TDP-43 and HuR-positive SGs. JNK inhibition also inhibited TDP-43 SG localization in cells acutely treated with sodium arsenite and reduced the number of aggregates per cell in cultures transfected with C-terminal TDP-43 162-414 and 219-414 constructs.

Conclusions

Our studies are the first to demonstrate a critical role for kinase control of TDP-43 accumulation in SGs and may have important implications for development of treatments for FTD and ALS, targeting cell signal pathway control of TDP-43 aggregation.     

Growth and reproductive responses to elevated CO2 in wild cereals of the northern Negev of Israel

How might wild relatives of modern cereals have responded to past, and how might they respond to future, atmospheric CO₂ enrichment under competitive situations in a dry, low‐nutrient environment? In order to test this, Aegilops and Hordeum species, common in semiarid annual grasslands of the Middle East, were grown in nine model ecosystems (400 kg each) with a natural matrix of highly diverse Negev vegetation established on native soil shipped to Basel, Switzerland. In a simulated, seasonally variable climate of the northern Negev, communities experienced a full life‐cycle in 280 (preindustrial), 440 (immediate future) and 600 ppm of CO₂ (end of the next century). Neither Aegilops (A. kotschyi and A. peregrina), nor Hordeum spontaneum showed a significant biomass response to CO₂ concentrations exceeding 280 ppm The reproductive output remained unaffected or even declined (A. peregrina) under elevated CO₂. Non‐structural carbohydrates in leaf tissues increased and N concentration decreased with increasing CO₂ concentration. N concentration, germination success and seedling development of newly formed grains were either unchanged or reduced in response to high CO₂ treatment of parent plants. In a separate fertilizer × CO₂ trial with A. kotschyi nested in smaller model communities, we found no effect of P addition, but a 2–3‐fold biomass increase by NPK addition compared to the unfertilized control. A significant stimulation of biomass by CO₂ enrichment (+ 44% between 280 and 600 ppm) was obtained only in the NPK treatment. These data suggest that increased CO₂ concentration had little direct effect on growth and reproduction in these ‘wild cereals’ in the recent past, and the same seems to hold for their future, except if N‐rich fertilizer is added.     

Use of fatty acids for the assessment of zooplankton grazing on bacteria, protozoans and microalgae

1. The distribution of fatty acids in different groups of bacteria, ciliated protozoans and microalgae is reviewed emphasizing specific fatty acids like odd-branched fatty acids and ( n -3) polyunsaturated fatty acids.
2. Odd-branched fatty acids and ( n -6) fatty acids appear to be good indicators of zooplankton grazing on bacteria and ciliates when they are detected in microcrustacean triacylglycerols. We give several examples where these fatty acids may be used as markers. The value of ( n -3) fatty acids in describing zooplankton grazing on phytoplankton seems to be low.     

Carbohydrate cytochemistry on hypodermic lymphatic endothelium of the green lizard,Lacerta hispanica

Summary A cytochemical study on the endothelium of the hypodermic lymphatic capillaries of the green lizard,Lacerta hispanica, has been carried out. The dialysed iron method produced a homogeneous precipitate on the surface of the endothelial cells and on the inside of the endocytic vesicles. The periodic acid-thiocarbohydrazide-silver proteinate, low pH phosphotungstic acid and high iron diamine techniques gave negative results. The carbohydrates in the capillaries thus seem to be glycosaminoglycans with carboxyl groups. The possible role of these glycosaminoglycans in the formation of the endocytic vesicles is discussed.