Protein tyrosine kinase Wee1B is essential for metaphase II exit in mouse oocytes

Waves of cyclin synthesis and degradation regulate the activity of Cdc2 protein kinase during the cell cycle. Cdc2 inactivation by Wee1B-mediated phosphorylation is necessary for arrest of the oocyte at G2-prophase, but it is unclear whether this regulation functions later during the metaphase-to-anaphase transition. We show that reactivation of a Wee1B pathway triggers the decrease in Cdc2 activity during egg activation. When Wee1B is down-regulated, oocytes fail to form a pronucleus in response to Ca(2+) signals. Calcium-calmodulin-dependent kinase II (CaMKII) activates Wee1B, and CaMKII-driven exit from metaphase II is inhibited by Wee1B down-regulation, demonstrating that exit from metaphase requires not only a proteolytic degradation of cyclin B but also the inhibitory phosphorylation of Cdc2 by Wee1B.     

Chemical and biochemical properties as potential indicators of disturbances

 The response of a series of soil microbial, chemical, and enzymatic chacacteristics to two different tillage systems (conventional and no-tillage) and two crop rotations (continuous corn and soybean–corn) was evaluated in a long-term field experiment in the Rolling Pampas Region, Marcos Juárez, Córdoba, Argentina. The parameters studied included: oxidizable, soluble and respiration C, total and hydrolyzable N, microbial activity, ammonifiers, nitrifiers, cellulolytic and total microflora, protease and urease activities. After 15 years, oxidizable C, total N and hydrolyzable N showed no differences regarding no-tillage systems. However, differences were found regarding control soil. While soluble C did not exhibit any significant differences, respiration C and microbial activity were indicators sensitive to different treatments. Enzymatic activities, protease in particular, did reflect changes due to management. Fluctuation in microbial population counts were more related to plant residues than to tillage systems. Received: 29 May 1999     

Role of secondary metabolites in the biocontrol activity of <Emphasis Type="Italic">Pseudomonas corrugata</Emphasis> and <Emphasis Type="Italic">Pseudomonas mediterranea</Emphasis>

Colletotrichum gloeosporioides is the causal agent of Camellia oleifera anthracnose, mainly infecting fruits and leaves. The fungus secretes degrading enzymes to destroy the cuticle of aerial plant parts and help infect the host successfully. To validate whether a cutinase gene (CglCUT1) was required for cutinase activity and pathogenicity of C. gloeosporioides, the CglCUT1 gene was cloned and analyzed. The characterization of CglCUT1 predicted protein suggests that the cloned DNA encoded a cutinase in C. gloeosporioides affecting C. oleifera. The CglCUT1 showed a high homology to those from C. gloeosporioides causing papaya anthracnose and C. capsici causing pepper anthracnose, as well as those of other ascomycetes. The whole CglCUT1 gene was knocked-out and the knockout mutant (?CglCUT39) was subsequently complemented using Agrobacterium tumefaciens mediated transformation. The knockout transformants exhibited significant decreases in cutinase activity and virulence compared with the wild-type strain. The complemented transformants of the disrupted transformant ?CglCUT39 showed a significant increase in cutinase activity and virulence compared with the disrupted transformant ?CglCUT39. This study suggests that the CglCUT1 gene has a positive effect on fungal virulence of the hemibiotrophic C. gloeosporioides on C. oleifera.     

Response of maize inbred lines to a defoliation treatment inducing tolerance to cold at germination

Defoliation during maize (Zea mays L.) kernel development has been observed to induce tolerance to cold of germinating seeds in responsive genotypes. The objectives of this study were to evaluate the response to defoliation of immature embryo and mature seed germinability at cold and to verify if the response was influenced by the developmental stage at which the treatment was applied. In three environments, six inbred lines (B73, IABO78, Lo1016, Lo964, Mo17, Os420) were defoliated (D) approximately 20 days after pollination (DAP) or not defoliated (ND). Immature embryos were excised three days after defoliation and germinated in vitro at 9 or 25 ^∘C. At maturation, kernel germination was tested at the same temperatures. Defoliation improved cold tolerance and mean time to germination (MTG) at 9 ^∘C of both embryos and kernels of Lo1016. To study the effect of kernel developmental stage on response to defoliation, plants of B73, Lo1016 and Lo964 were defoliated at 15, 18, 21, 24, 27, 30, 33, 36, and 39 DAP, or not defoliated. At the same DAP, immature grains were analyzed for dry weight, water and abscisic acid (ABA) content. In Lo1016, low amounts of kernel ABA were detected at all stages, while in Lo964 and B73 ABA increased during development. Lo1016 mature kernels showed an improvement of cold tolerance due to defoliation at all times, while the other genotypes did not. In conclusion inbred lines showed variability for mature seed and immature embryo tolerance to cold at germination and for the ability to acquire tolerance after defoliation.     

<Emphasis Type="Italic">Vicia faba</Emphasis> plants respond to oviposition by invasive <Emphasis Type="Italic">Halyomorpha halys</Emphasis> activating direct defences against offspring

The invasive stink bug Halyomorpha halys is established in many European and American agro-ecosystems, where it causes severe crop losses. Potential control measures might include enhancement of plant defences. When attacked by herbivorous insects that oviposit on it, the plant may respond by priming direct defences, which might affect the development of future brood. Halyomorpha halys attacks numerous plant species in the invaded areas. Here, we investigated whether Vicia faba plants challenged by H. halys females can impair the development of its offspring through the activation of induced direct defences. We measured the weight and dimension of nymphs that developed on oviposition-experienced plants after 7 and 17 days from hatching. Nymphs that developed on oviposition-experienced plants weighed less compared to those that developed either on control plants or on plants solely subjected to H. halys feeding, and third instars showed shorter dimensions (tibia length). In addition, when oviposition-experienced plants were attacked by nymphs, higher and more rapid expression of two jasmonic acid-dependent genes (cysteine proteinase inhibitor gene and NAI1) was detected, possibly due to a mechanism of priming. Increased expression of the salicylic acid-responsive PR1 gene was also detected in egg-experienced plants, although the response was delayed compared to JA-dependent genes. Our results suggest that V. faba plants recognize H. halys oviposition as a warning signal and pre-activate defences against future nymphal herbivory.     

Hyptis suaveolens and Hyptis spicigera (Lamiaceae) essential oils: qualitative analysis, contact toxicity and repellent activity against Sitophilus granarius (L.) (Coleoptera: Dryophthoridae)

Essential oils from Hyptis suaveolens (L.) Poiteau (Lamiaceae) and Hyptis spicigera Lamarck (Lamiaceae) were first analysed by gas chromatography and by gas chromatography/electron impact mass spectroscopy and then evaluated for toxicity and repellent activity against Sitophilus granarius (L.) (Coleoptera: Dryophthoridae), one of the most serious worldwide stored grain pests. Fifty-six compounds have been identified in the essential oil of H. suaveolens: monoterpene hydrocarbons were the most represented volatiles (64.1%), followed by sesquiterpene hydrocarbons (24.0%), oxygenated monoterpenes (8.1%) and oxygenated sesquiterpenes (2.4%). Diterpenes and non-terpene derivatives were scarcely represented. Sixty compounds have been identified in the essential oil of H. spicigera: monoterpene hydrocarbons were the most represented class of volatiles (70.4%), followed by sesquiterpene hydrocarbons (22.6%). Results from topical applications on insects showed that both essential oils had an effective insecticidal activity. The complete kill of S. granarius was observed 24 h after treatment at a minimum effective dose of 0.4 and 0.6 μl per insect with H. suaveolens and H. spicigera oil, respectively. Results from repellency tests showed that the two essential oils had a repellent activity on S. granarius adults: at the lowest dose (2 × 10⁻⁴ μl oil per cm²), H. spicigera essential oil exhibited a higher repellent effect in comparison to H. suaveolens. No significant differences were observed for the repellent effect between the two essential oils at the highest dose (2 × 10⁻² μl oil per cm²).     

Ethnobotanical knowledge of the Istro-Romanians of Zejane in Croatia

An ethno-pharmacognostic survey was carried out in one of the smallest ethnic and linguistic groups in Europe: the Istro-Romanians of the village of Zejane (in Croatia), which has a population of approximately 140 persons, mainly elderly. Using an intensive field participant observation methodology, we recorded about 60 remedies of the local folk pharmacopoeia, and mainly derived from plants. Among them, the uncommon traditions to use homemade vinegar from wild apple (Malus sylvestris) and Cornelian cherries (Cornus mas) for diverse medical purposes, and houseleek (Sempervivum tectorum) against ear pains have been briefly discussed.     

Effect of inhibitors of cytoplasmic structures and functions on rabies virus infection in vitro

The effect in vitro of some cytoplasmic structure and function inhibitors on the different stages of rabies virus infection was investigated. Treatment of fibroblasts (CER) and human neuroblastoma cells (IMR-32) with substances acting on low pH intracellular compartments (methylamine and monensin) prevented rabies virus genome delivery in the cytosol. An early inhibition of viral infection was also obtained in the presence of B and D cytochalasins and trifluoperazine which interact with microfilament structures. Treatment with colchicine and vinblastine did not affect rabies multiplication, suggesting that microtubules are not involved in this process. However, the multiplication of prebound virions did not take place in the presence of inhibitors of oxidative phosphorylation (sodium azide and CCCP) and of glycolysis (2-deoxy-D-glucose) indicating that rabies virus replication is largely energy-dependent in both host cells examined.