Ozone Sensitivity in Hybrid Poplar Is Correlated with a Lack of Defense-Gene Activation

Ozone is a major gaseous pollutant thought to contribute to forest decline. Although the physiological and morphological responses of forest trees to ozone have been well characterized, little is known about the molecular basis for these responses. Our studies compared the response to ozone of ozone-sensitive and ozone-tolerant clones of hybrid poplar (Populus maximowizii × Populus trichocarpa) at the physiological and molecular levels. Gas-exchange analyses demonstrated clear differences between the ozone-sensitive clone 388 and the ozone-tolerant clone 245. Although ozone induced a decrease in photosynthetic rate and stomatal conductance in both clones, the magnitude of the decrease in stomatal conductance was significantly greater in the ozone-tolerant clone. RNA-blot analysis established that ozone-induced mRNA levels for phenylalanine ammonia-lyase, O-methyltransferase, a pathogenesis-related protein, and a wound-inducible gene were significantly higher in the ozone-tolerant than in the ozone-sensitive plants. Wound- and pathogen-induced levels of these mRNAs were also higher in the ozone-tolerant compared with the ozone-sensitive plants. The different physiological and molecular responses to ozone exposure exhibited by clones 245 and 388 suggest that ozone tolerance involves the activation of salicylic-acid- and jasmonic-acid-mediated signaling pathways, which may be important in triggering defense responses against oxidative stress.     

Physiological studies on pea tendrils. XII. Effects of temperature on contact coiling and uncoiling

When excised tendrils of pea ( Pisum sativum L. cv. Alaska 2B) are mechanically perturbed and allowed to coil at different constant temperatures, the greatest amount of coiling occurs between 27°C and 33°C. Coiling of tendrils continues for about 2 h after mechanical perturbation at which time uncoiling usually begins. The temperature at which the rate of uncoiling is greatest appears to be influenced, at least in part, by the temperature at which the tendrils coiled. For example, when tendrils coil at 20°C their rate of uncoiling at 20°C is less than if they had coiled at 23°C. Estimated activation energies for the uncoiling process are greater than for coiling, with 35 J/mol × s and 97 J/mol × s for uncoiling in the temperature ranges 18°C to 23°C and 10°C to 18°C, respectively. The estimated activation energy for coiling is 5.4 J/mol × s. It is suggested that the process of tendril uncoiling, as well as tendril coiling, might be an active, energy requiring process.
When mechanically perturbed tendrils are placed in the cold (5°C) they do not coil. But this interruption of the coiling process with a cold (5°C) treatment, either immediately after mechanical perturbation or after coiling has begun, does not prevent coiling from continuing after tendrils are again given a more suitable temperature. It is concluded that the cessation of coiling during the cold period may be due to a slowdown in metabolism. It is suggested that there may be a factor which is responsible for the motor response and which is retained during the cold treatment.     

Lipovitellin-phosvitin crystals with orthorhombic features: thin-section electron microscopy, gel electrophoresis, and microanalysis in teleost and amphibian yolk platelets and a comparison with other vertebrates

Yolk-platelet crystals in the teleosts Pelvicachromis pulcher and Noemacheilus barbatulus and the amphibians Xenopus laevis, Rana temporaria, R. esculenta, and Triturus sp. have been studied by electron diffraction and imaging using a standardized processing (glutaraldehyde-osmium tetroxide fixation, glutaraldehyde-urea embedding, thin-section staining), by X-ray microanalysis, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of their constituents. The crystal lattice is orthorhombic having--following standardized processing--in three amphibians a = 9.0 nm, b = 17.6 nm, c = 19.2 nm, and in the two teleosts a = 8.9 nm, b = 17.6 nm, c = 20.0 nm (averages). These values are very close to X-ray data from wet crystals (Xenopus laevis). Crystal images in the three axial projections point to the presence of space group P212121 (or an approximation of it since the lipovitellin dimers cannot be fully equivalent in some cases), to differences between the phosvitins of the two teleosts, and to a highly unusual stain exclusion from large crystal constituents interpreted as representing lipovitellin dimers. Microanalysis in ultrathin cryosections and other preparations revealed K and Cl to be the prominent ions in the crystals (and in the superficial layer of the platelet). Gel electrophoresis (including data of cyclostomes) showed considerable molecular variations despite a closely similar crystal architecture, emphasizing a physiological significance of the architecture, which may have remained conserved for nearly 400 million years according to paleontologic views.     

Die Oocyten der GrundelPomatoschistus minutus

The egg membrane and follicle of the oocytes ofPomatoschistus minutus were investigated by light and electron microscopy. The formation of the cortex radiatus begins in late stage I and is concluded in stage III. In stage II bundle structures appear at the base of the cortex radiatus. These bundle structures cannot be identified in stage III. The cortex radiatus differentiates into the cortex radiatus externus and the cortex radiatus internus. Up to 220 attaching filaments originate in stage II. They are connected with the egg membrane at the animal pole. The attaching filaments are a modified part of the cortex radiatus externus. They consist of two substances which differ in their electron density. The attaching filaments lie between the cells of the follicle epithelium and are probably formed by these cells. They are adapted for attaching the eggs. The follicle epithelium is always single-layered. The cross-section of the spindle-shaped follicle cells is quadratic in stage I and II and quadrilateral in stage III. The cells of the follicle epithelium contain a lot of rough ER and are thus divided into many compartments. The primary oocyte membrane (oolemma) shows considerable pinocytosis activity in stage II and there are many polysomes in the peripheral cytoplasm. Possible functions of the pinocytotic vesicles and the polysomes are discussed.     

Effect of elongation factor Tu on the conformation of phenylalanyl-tRNAPhe

Structural features of the tRNAPhe molecule upon ternary complex formation with the bacterial elongation factor Tu were investigated. Phosphodiester bonds at positions 18 and 34 were found to be labilized in bound tRNA. Conversely, a higher stability of the phosphodiester links at positions 20, 21 and 36 was detected. Using ethylnitrosourea as a chemical probe a conformational change occurring at phosphate position 53 was observed in complexed tRNA. These results are interpreted by a structural rearrangement of the nucleic acid induced by complex formation.     

Localization of carbonic anhydrase in identified glial cells of the leech central nervous system: application of histochemical and immunocytochemical methods

We localized the enzyme carbonic anhydrase (CA) in frozen sections of the leech (Hirudo medicinalis) central nervous system by two histochemical techniques and the indirect immunofluorescence technique. Hansson's cobalt precipitation method and the use of 1-dimethylamino-naphthalene-5-sulfonamide (DNSA) to build a fluorescent enzyme-substrate complex showed that glial cells are the sites of CA activity in the leech. Neuropil and connective glial cells surrounding the axons had strong CA activity, whereas packet glial cells, which surround neuron cell bodies, and neurons themselves remained unstained. Glial cells reacted markedly with FITC-coupled antibodies against CA isoenzyme II, but experiments with antibodies against CA isoenzyme I showed no reaction.     

Mid-Holocene vegetation change in the Troad (W Anatolia): man-made or natural?

New wood charcoal data from two archaeological sites in western Anatolia (Kumtepe and Troy/Çanakkale province) enabled a review of earlier reconstruction of the mid-Holocene vegetation and land use patterns in the region. Multi-proxy data from archaeology, zooarchaeology and climatology are combined to evaluate the relationship of climate-induced and man-made environmental change for a period spanning the Late Neolithic to the Early Bronze Age (ca. 5000–2450 cal b.c.). During the first settlement period (Kumtepe A: ca. 5000–4600 cal b.c.) lush vegetation with high proportions of deciduous oak and pine prevailed, enabling the intense use of natural resources by the late Neolithic population, which use might be reflected in the first few representatives of maquis vegetation. A settlement hiatus at the site between roughly 4600 and 3500 cal b.c. includes a cooling event in the Aegean and may have supported persistence and/or development of open vegetation units. However, the hiatus may have ended with a period of regeneration of the vegetation. From Kumtepe B2 (ca. 3300 cal b.c.) onward, human impact becomes clearly visible, although the main woodland taxa continue to prevail. In all, environmental and economic dynamics between 5000 and 2300 cal b.c. in the Troad can be characterised as at least two alternating developmental sequences of climate-induced vegetation change and reinforcement of woodland degradation by human activity.     

Genetic diversity of Cedrela fissilis (Meliaceae) in the Brazilian Atlantic Forest reveals a complex phylogeographic history driven by Quaternary climatic fluctuations

Quaternary climatic fluctuations have shaped the geographic distribution of lineages, potentially affecting the demography, genetic structure, and patterns of genetic diversity of extant species. Different phylogeographic scenarios have been proposed for plants in neotropical cloud forests during the Last Glacial Maximum based on paleoecological data: the dry refugia hypothesis (DRH) and the moist forest hypothesis. We specifically focus on the Brazilian Atlantic Forest (BAF) range of Cedrela fissilis (Meliaceae), sampling 410 specimens from 50 localities. Our study combines analyses of the genetic diversity, phylogeographic patterns, and past geographic distributions with a particular focus on highland populations. We identified 283 alleles across the 11 microsatellite loci, ranging from 18 to 33 alleles per locus, distributed across five genetic groups. Most populations of C. fissilis from the BAF exhibited a diffuse genetic structure, reflected in low pairwise F_ST values, which could be the consequence of high gene flow. In addition, the plastid data showed a connection between the western, southern, and eastern populations in the North‐East of Brazil, but no association between genetic data and elevation was observed. Habitat suitability projections over the past 140 000 years showed less fragmentation relative to the present, indicating a higher connectivity and gene flow. Our results provide support for both the moist forest as well as the DRH, suggesting that most likely, a mixture of these processes has acted through space and time.