Plasticity of parental CENH3 incorporation into the centromeres in wheat × barley F1 hybrids

Incorporating the centromere-specific histone H3 protein CENH3 into the centromeric nucleosomes is indispensable for accurate centromere function and balanced chromosome segregation in most eukaryotes, including higher plants. In the cell nuclei of interspecific hybrids, divergent centromeric DNAs cohabit and lead the corresponding parental chromosomes through the mitotic and meiotic cell divisions. Depending on the transmission of the parental chromosomes carrying the CENH3-encoding genes, CENH3 proteins from one or both parents may be present in these hybrids. The incorporation of parental CENH3 proteins into the divergent centromeres and their role in the chromosome elimination process in interspecific hybrids is still poorly understood. Here, we produced wheat × barley F1 hybrids that carried different combinations of barley chromosomes with genes encoding for either one (αCENH3) or both barley CENH3 protein variants (α- and βCENH3). We generated specific antibodies distinguishing between the wheat CENH3 proteins and barley αCENH3 and applied them together with FISH probes to detect the precise pattern of parental CENH3 deposition into the wheat and barley centromeric nucleosomes. Analysis of somatic and meiotic nuclei of the wheat × barley hybrids revealed the plasticity of the maternal (wheat) CENH3 proteins to become incorporated into the paternal (barley) centromeric nucleosomes. However, no evidence for paternal CENH3 plasticity was detected in this study. The significance of the unilateral centromere plasticity and possible patterns of CENH3 incorporation into centromeres in interspecific hybrids are discussed.

Heat stress during male meiosis impairs cytoskeletal organization, spindle assembly and tapetum degeneration in wheat

The significance of heat stress in agriculture is ever-increasing with the progress of global climate changes. Due to a negative effect on the yield of staple crops, including wheat, the impairment of plant reproductive development triggered by high ambient temperature became a restraint in food production. Although the heat sensitivity of male meiosis and the following gamete development in wheat has long been recognized, a detailed structural characterization combined with a comprehensive gene expression analysis has not been done about this phenomenon. We demonstrate here that heat stress severely alters the cytoskeletal configuration, triggers the failure of meiotic division in wheat. Moreover, it changes the expression of genes related to gamete development in male meiocytes and the tapetum layer in a genotype-dependent manner. 'Ellvis', a heat-tolerant winter wheat cultivar, showed high spikelet fertility rate and only scarce structural aberrations upon exposure to high temperature. In addition, heat shock genes and genes involved in scavenging reactive oxygen species were significantly upregulated in 'Ellvis', and the expression of meiosis-specific and major developmental genes showed high stability in this cultivar. In the heat-sensitive 'Mv 17-09', however, genes participating in cytoskeletal fiber nucleation, the spindle assembly checkpoint genes, and tapetum-specific developmental regulators were downregulated. These alterations may be related to the decreased cytoskeleton content, frequent micronuclei formation, and the erroneous persistence of the tapetum layer observed in the sensitive genotype. Our results suggest that understanding the heat-sensitive regulation of these gene functions would be an essential contribution to the development of new, heat-tolerant cultivars.

Morpho-Anatomical, Physiological and Biochemical Adjustments in Response to Heat and Drought Co-Stress in Winter Barley

This study aimed to investigate the combined effect of high temperatures 10 °C above the optimum and water withholding during microgametogenesis on vegetative processes and determine the response of winter barley genotypes with contrasting tolerance. For this purpose, two barley varieties were analyzed to compare the effect of heat and drought co-stress on their phenology, morpho-anatomy, physiological and biochemical responses and yield constituents. Genotypic variation was observed in response to heat and drought co-stress, which was attributed to differences in anatomy, ultrastructure and physiological and metabolic processes. The co-stress-induced reduction in relative water content, total soluble protein and carbohydrate contents, photosynthetic pigment contents and photosynthetic efficiency of the sensitive Spinner variety was significantly greater than the tolerant Lambada genotype. Based on these observations, it has been concluded that the heat-and-drought stress-tolerance of the Lambada variety is related to the lower initial chlorophyll content of the leaves, the relative resistance of photosynthetic pigments towards stress-triggered degradation, retained photosynthetic parameters and better-preserved leaf ultrastructure. Understanding the key factors underlying heat and drought co-stress tolerance in barley may enable breeders to create barley varieties with improved yield stability under a changing climate.

Global transcriptome and targeted metabolite analyses of roots reveal different defence mechanisms against Ralstonia solanacearum infection in two resistant potato cultivars

Ralstonia solanacearum (Rs), the causal agent of bacterial wilt disease in an unusually wide range of host plants, including potato (Solanum tuberosum), is one of the most destructive phytopathogens that seriously reduces crop yields worldwide. Identification of defence mechanisms underlying bacterial wilt resistance is a prerequisite for biotechnological approaches to resistance breeding. Resistance to Rs has been reported only in a few potato landraces and cultivars. Our in vitro inoculation bioassays confirmed that the cultivars 'Calalo Gaspar' (CG) and 'Cruza 148' (CR) are resistant to Rs infection. Comparative transcriptome analyses of CG and CR roots, as well as of the roots of an Rs-susceptible cultivar, 'Désirée' (DES), were carried out two days after Rs infection, in parallel with their respective noninfected controls. In CR and DES, the upregulation of chitin interactions and cell wall-related genes was detected. The phenylpropanoid biosynthesis and glutathione metabolism pathways were induced only in CR, as confirmed by high levels of lignification over the whole stele in CR roots six days after Rs infection. At the same time, Rs infection greatly increased the concentrations of chlorogenic acid and quercetin derivatives in CG roots as it was detected using ultra-performance liquid chromatography - tandem mass spectrometry. Characteristic increases in the expression of MAP kinase signalling pathway genes and in the concentrations of jasmonic, salicylic, abscisic and indoleacetic acid were measured in DES roots. These results indicate different Rs defence mechanisms in the two resistant potato cultivars and a different response to Rs infection in the susceptible cultivar.

Peanut stunt virus movement protein is the limiting factor in Capsicum annuum infection

Cucumber mosaic virus (CMV) is one of the most devastating plant viruses, with more than 1,200 species of host plants. The host range and economic importance of peanut stunt virus (PSV) are mostly limited to legumes, despite the similar taxonomy and genome structure with CMV. Since no data are available on the background of the limited host range of PSV, RNA 3 recombinant and reassortant viruses were generated (C12P3, P12C3, C12CP3, C12PC3, C12PΔC3) to study their infection phenotype on a common host (Nicotiana benthamiana) and on a selective host (Capsicum annuum cv. Brody). The PSV movement protein (MP) was not able to function with the coat protein (CP) of CMV unless the C-terminal 42 amino acids were deleted from the PSV MP. As a result of the inoculation experiments, MP was considered the protein influencing symptom phenotypes on N. benthamiana and responsible for the host range difference on the pepper. Since plasmodesmata (PD) localization of viral MPs is essential for cell-to-cell movement, subcellular localization of GFP-tagged MPs (CMV-MP-eGFP, PSV-MP-eGFP) was observed. In the case of CMV-MP-eGFP, clear colocalization with PD was detected in both hosts, but PSV-MP-eGFP was not tightly connected to the PD in N. benthamiana and barely localized to the PD in C. annuum epidermal cells. Measuring Pearson correlation coefficients (PCCs) also supported the visual observation.

Pericentromeric chromatin reorganisation follows the initiation of recombination and coincides with early events of synapsis in cereals

The reciprocal exchange of genetic information between homologous chromosomes during meiotic recombination is essential to secure balanced chromosome segregation and to promote genetic diversity. The chromosomal position and frequency of reciprocal genetic exchange shapes the efficiency of breeding programmes and influences crop improvement under a changing climate. In large genome cereals, such as wheat and barley, crossovers are consistently restricted to subtelomeric chromosomal regions, thus preventing favourable allele combinations being formed within a considerable proportion of the genome, including interstitial and pericentromeric chromatin. Understanding the key elements driving crossover designation is therefore essential to broaden the regions available for crossovers. Here, we followed early meiotic chromatin dynamism in cereals through the visualisation of a homologous barley chromosome arm pair stably transferred into the wheat genetic background. By capturing the dynamics of a single chromosome arm at the same time as detecting the undergoing events of meiotic recombination and synapsis, we showed that subtelomeric chromatin of homologues synchronously transitions to an open chromatin structure during recombination initiation. By contrast, pericentromeric and interstitial regions preserved their closed chromatin organisation and become unpackaged only later, concomitant with initiation of recombinatorial repair and the initial assembly of the synaptonemal complex. Our results raise the possibility that the closed pericentromeric chromatin structure in cereals may influence the fate decision during recombination initiation, as well as the spatial development of synapsis, and may also explain the suppression of crossover events in the proximity of the centromeres.

The 28 Ser Amino Acid of Cucumber Mosaic Virus Movement Protein Has a Role in Symptom Formation and Plasmodesmata Localization

Cucumber mosaic virus (CMV, Cucumovirus, Bromoviridae) is an economically significant virus infecting important horticultural and field crops. Current knowledge regarding the specific functions of its movement protein (MP) is still incomplete. In the present study, potential post-translational modification sites of its MP were assayed with mutant viruses: MP/S28A, MP/S28D, MP/S120A and MP/S120D. Ser28 was identified as an important factor in viral pathogenicity on Nicotiana tabacum cv. Xanthi, Cucumis sativus and Chenopodium murale. The subcellular localization of GFP-tagged movement proteins was determined with confocal laser-scanning microscopy. The wild type movement protein fused to green fluorescent protein (GFP) (MP-eGFP) greatly colocalized with callose at plasmodesmata, while MP/S28A-eGFP and MP/S28D-eGFP were detected as punctate spots along the cell membrane without callose colocalization. These results underline the importance of phosphorylatable amino acids in symptom formation and provide data regarding the essential factors for plasmodesmata localization of CMV MP.

Translating Scientific Knowledge to Government Decision Makers Has Crucial Importance in the Management of the COVID-19 Pandemic

In times of epidemics and humanitarian crises, it is essential to translate scientific findings into digestible information for government policy makers who have a short time to make critical decisions. To predict how far and fast the disease would spread across Hungary and to support the epidemiological decision-making process, a multidisciplinary research team performed a large amount of scientific data analysis and mathematical and socioeconomic modeling of the COVID-19 epidemic in Hungary, including modeling the medical resources and capacities, the regional differences, gross domestic product loss, the impact of closing and reopening elementary schools, and the optimal nationwide screening strategy for various virus-spreading scenarios and R metrics. KETLAK prepared 2 extensive reports on the problems identified and suggested solutions, and presented these directly to the National Epidemiological Policy-Making Body. The findings provided crucial data for the government to address critical measures regarding health care capacity, decide on restriction maintenance, change the actual testing strategy, and take regional economic, social, and health differences into account. Hungary managed the first part of the COVID-19 pandemic with low mortality rate. In times of epidemics, the formation of multidisciplinary research groups is essential for policy makers. The establishment, research activity, and participation in decision-making of these groups, such as KETLAK, can serve as a model for other countries, researchers, and policy makers not only in managing the challenges of COVID-19, but in future pandemics as well.

Stigma Functionality and Fertility Are Reduced by Heat and Drought Co-stress in Wheat

As a consequence of climate change, unpredictable extremely hot and dry periods are becoming more frequent during the early stages of reproductive development in wheat (Triticum aestivum L.). Pollen sterility has long been known as a major determinant of fertility loss under high temperature and water scarcity, but it will be demonstrated here that this is not the exclusive cause and that damage to female reproductive organs also contributes to losses of fertility and production. Changes in the phenology, morphology, and anatomy of female reproductive cells and organs, in the ROS and RNS generation of stigmatic papilla cells, and in fertility and yield components in response to simultaneous high temperature and drought at gametogenesis were studied in two wheat genotypes with contrasting stress responses. The combination of high temperature (32/24°C) and total water withdrawal for 5 days at gametogenesis altered the phenology of the plants, reduced pollen viability, modified the morphology and the anatomy of the pistils, enhanced the generation of ROS and RNS, intensified lipid peroxidation and decreased the NO production of stigmatic papilla cells, all leading to reduced fertility and to production loss in the sensitive genotype, depending on the position of the floret on the spike. Reduced functionality of female and male reproductive parts accounted for 34% and 66%, respectively, of the total generative cell- and organ-triggered fertility loss.

A single point mutation on the cucumber mosaic virus surface induces an unexpected and strong interaction with the F1 complex of the ATP synthase in Nicotiana clevelandii plants

A previous study showed that a single amino acid difference in the cucumber mosaic virus (CMV) capsid protein (CP) elicits unusual symptoms. The wild-type strain (CMV-R) induces green mosaic symptoms and malformation while the mutant strain (CMV-R3E79R) causes chlorotic lesions on inoculated leaves and strong stunting with necrosis on systemic leaves. Virion preparations of CMV-R and CMV-R3E79R were partially purified from Nicotiana clevelandii A. Gray and analysed by two-dimensional gel electrophoresis. Their separated protein patterns showed remarkable differences at the 50-75 kDa range, both in numbers and intensity of spots, with more protein spots for the mutant CMV. Mass spectrometry analysis demonstrated that the virion preparations contained host proteins identified as ATP synthase alpha and beta subunits as well as small and large Rubisco subunits, respectively. Virus overlay protein binding assay (VOPBA), immunogold electron microscopy and modified ELISA experiments were used to prove the direct interaction between the virus particle and the N. clevelandii ATP synthase F1 motor complex. Protein-protein docking study revealed that the electrostatic change in the mutant CMV can introduce stronger interactions with ATP synthase F1 complex. Based on our findings we suggest that the mutation present in the CP can have a direct effect on the long-distance movement and systemic symptoms. In molecular view the mutant CMV virion can lethally block the rotation of the ATP synthase F1 motor complex which may lead to cell apoptosis, and finally to plant death.

ImmunoFISH: Simultaneous Visualisation of Proteins and DNA Sequences Gives Insight Into Meiotic Processes in Nuclei of Grasses

ImmunoFISH is a method combining immunolabelling (IL) with fluorescent in situ hybridisation (FISH) to simultaneously detect the nuclear distribution of proteins and specific DNA sequences within chromosomes. This approach is particularly important when analysing meiotic cell division where morphogenesis of individual proteins follows stage-specific changes and is accompanied by a noticeable chromatin dynamism. The method presented here is simple and provides reliable results of high quality signal, low background staining and can be completed within 2 days following preparation. Conventional widefield epifluorescent or laser scanning microscopy can be used for high resolution and three-dimensional analysis. Fixation and preparation techniques were optimised to best preserve nuclear morphology and protein epitopes without the need for any antigen retrieval. Preparation of plant material involved short cross-linking fixation of meiotic tissues with paraformaldehyde (PFA) followed by enzyme digestion and slide-mounting. In order to avoid rapid sample degradation typical of shortly fixed plant materials, and to be able to perform IL later, slides were snap-frozen and stored at -80°C. Ultra-freezing produced a remarkable degree of structural preservation for up to 12 months, whereby sample quality was similar to that of fresh material. Harsh chemicals and sample dehydration were avoided throughout the procedure and permeability was ensured by a 0.1-0.3% detergent treatment. The ImmunoFISH method was developed specifically for studying meiosis in Triticeae, but should also be applicable to other grass and plant species.

Comprehensive Analysis of DWARF14-LIKE2 (DLK2) Reveals Its Functional Divergence from Strigolactone-Related Paralogs

Strigolactones (SLs) and related butenolides, originally identified as active seed germination stimulants of parasitic weeds, play important roles in many aspects of plant development. Two members of the D14 α/β hydrolase protein family, DWARF14 (D14) and KARRIKIN INSENSITIVE2 (KAI2) are essential for SL/butenolide signaling. The third member of the family in Arabidopsis, DWARF 14-LIKE2 (DLK2) is structurally very similar to D14 and KAI2, but its function is unknown. We demonstrated that DLK2 does not bind nor hydrolyze natural (+)5-deoxystrigol [(+)5DS], and weakly hydrolyzes non-natural strigolactone (-)5DS. A detailed genetic analysis revealed that DLK2 does not affect SL responses and can regulate seedling photomorphogenesis. DLK2 is upregulated in the dark dependent upon KAI2 and PHYTOCHROME INTERACTING FACTORS (PIFs), indicating that DLK2 might function in light signaling pathways. In addition, unlike its paralog proteins, DLK2 is not subject to rac-GR24-induced degradation, suggesting that DLK2 acts independently of MORE AXILLARY GROWTH2 (MAX2); however, regulation of DLK2 transcription is mostly accomplished through MAX2. In conclusion, these data suggest that DLK2 represents a divergent member of the DWARF14 family.

Powdery Mildew Resistance in Wheat Cultivar Mv Hombár is Conferred by a New Gene, PmHo

A new powdery mildew resistance gene designated as PmHo was identified in 'Mv Hombár' winter wheat, bred in Martonvásár, Hungary. It has exhibited a high level of resistance over the last two decades. Genetic mapping of recombinant inbred lines derived from the cross 'Ukrainka'/Mv Hombár located this gene on chromosome 2AL. The segregation ratio and consistent effect in all environments indicated that PmHo is a major dominant powdery mildew resistance gene. The race-specific nature of resistance in Mv Hombár was shown by the emergence of a single virulent pathotype designated as 51-Ho. This pathotype was, to some extent, able to infect Mv Hombár, developing visible symptoms with sporulating colonies. Microscopic studies revealed that, in incompatible interactions, posthaustorial hypersensitivity reaction was the most prevalent but not exclusive plant defense response in Mv Hombár, and fungal growth was mostly arrested during haustorium formation or in the early stages of colony development. The delayed fungal development of the virulent pathotype 51-Ho may be explained by additional effects of other loci that were also involved in the powdery mildew resistance of Mv Hombár.

New Insights into the Life Cycle of the Wheat Powdery Mildew: Direct Observation of Ascosporic Infection in Blumeria graminis f. sp. tritici

Although Blumeria graminis is an intensively studied pathogen, an important part of its life cycle (namely, the way ascospores initiate primary infections on cereal leaves) has not yet been explored in detail. This study reports, for the first time, the direct observation of this process in B. graminis f. sp. tritici using light and confocal laser-scanning microscopy. All the germinated ascospores produced a single germ tube type both in vitro and on host plant surfaces; therefore, the ascosporic and conidial germination patterns are markedly different in this fungus, in contrast to other powdery mildews. Germinated ascospores penetrated the epidermal cells of wheat leaves and produced haustoria as known in the case of conidial infections. This work confirmed earlier studies reporting that B. graminis chasmothecia collected from the field do not contain mature ascospores, only asci filled with protoplasm; ascospore development is induced by moist conditions and is a fast process compared with other powdery mildews. Although ascosporic infections are frequent in B. graminis f. sp. tritici in the field, as shown by this study and other works as well, a recent analysis of the genomes of four isolates revealed the signs of clonal or near-clonal reproduction. Therefore, chasmothecia and ascospores are probably more important as oversummering structures than genetic recombination factors in the life cycle of this pathogen.

A morpho-physiological approach differentiates bread wheat cultivars of contrasting tolerance under cyclic water stress

Leaf micromorphological traits and some physiological parameters with potential relevance to drought tolerance mechanisms were investigated in four selected winter wheat varieties. Plants were subjected to two cycles of drought treatment at anthesis. Yield components confirmed contrasting drought-sensitive and -tolerant behavior of the genotypes. Drought tolerance was associated with small flag leaf surfaces and less frequent occurrence of stomata. Substantial variation of leaf cuticular thickness was found among the cultivars. Thin cuticle coincided with drought sensitivity and correlated with a high rate of dark-adapted water loss from leaves. Unlike in Arabidopsis, thickening of the cuticular matrix in response to water deprivation did not occur. Water stress induced epicuticular wax crystal depositions preferentially on the abaxial leaf surfaces. According to microscopy and electrolyte leakage measurements from leaf tissues, membrane integrity was lost earlier or to a higher extent in sensitive than in tolerant genotypes. Cellular damage and a decline of relative water content of leaves in sensitive cultivars became distinctive during the second cycle of water deprivation. Our results indicate strong variation of traits with potential contribution to the complex phenotype of drought tolerance in wheat genotypes. The maintained membrane integrity and relative water content values during repeated water limited periods were found to correlate with drought tolerance in the selection of cultivars investigated.

Embryo and endosperm development in wheat (Triticum aestivum L.) kernels subjected to drought stress

The aim of the present work was to reveal the histological alterations triggered in developing wheat kernels by soil drought stress during early seed development resulting in yield losses at harvest. For this purpose, observations were made on the effect of drought stress, applied in a controlled environment from the 5th to the 9th day after pollination, on the kernel morphology, starch content and grain yield of the drought-sensitive Cappelle Desprez and drought-tolerant Plainsman V winter wheat (Triticum aestivum L.) varieties. As a consequence of water withdrawal, there was a decrease in the size of the embryos and the number of A-type starch granules deposited in the endosperm, while the development of aleurone cells and the degradation of the cell layers surrounding the ovule were significantly accelerated in both genotypes. In addition, the number of B-type starch granules per cell was significantly reduced. Drought stress affected the rate of grain filling shortened the grain-filling and ripening period and severely reduced the yield. With respect to the recovery of vegetative tissues, seed set and yield, the drought-tolerant Plainsman V responded significantly better to drought stress than Cappelle Desprez. The reduction in the size of the mature embryos was significantly greater in the sensitive genotype. Compared to Plainsman V, the endosperm cells of Cappelle Desprez accumulated significantly fewer B-type starch granules. In stressed kernels of the tolerant genotype, the accumulation of protein bodies occurred significantly earlier than in the sensitive variety.

New phenotypes of the drought-tolerant cbp20 Arabidopsis thaliana mutant have changed epidermal morphology

This paper provides a detailed phenotypic analysis of the abscisic acid (ABA) hypersensitive Cap Binding Protein 20 (cbp20) mutant. Some hitherto undescribed changes were found in the tissue structure and epidermal morphology of this mutant. These include more and smaller cells in the epidermis, a thicker cuticle and more frequent occurrence of trichomes on leaf surfaces. Some of these traits may contribute to the physiological processes responsible for the water-saving behaviour of the mutant. Abnormal spatial patterns between stomatal pore complexes were also found on various organs of the mutant. All these observations indicate profoundly disturbed development of epidermal tissue in the cbp20 mutant, which has not previously been reported for this class of mutants. A potential connection between the new phenotypes and disturbed miRNA metabolism and mRNA splicing of the mutant is discussed.

Low and high ψ ways from post-transcriptional RNA regulation to drought tolerance

Plants withstand adverse environmental effects by stress responses governed by a complex multilayer regulatory network. Besides well established transcriptional cascades posttranscriptional modifications give more plasticity to the plant's behavior under unfavorable circumstances. These modifications include various RNA alterations typically interlaced with transcriptional or translational regulation. Recent examples have been described in RNA splicing, processing, translation and degradation, some of which operate through effects of small non-coding RNAs. So far details of physiological output mechanisms affected by RNA regulation have been uncovered in a few cases only, some of those will be detailed in this review. In the well documented example of the nuclear cap binding complex (nCBC) mutants, molecular mechanisms of the regulatory switch and downstream events have been established in detail. New results directly link nCBC function to splicing, RNA processing and abscisic acid (ABA). Potential output mechanisms of this control point have also been implicated, both in fast stress responses and in developmental regulation. This latter aspect provides a new insight into how RNA regulation may contribute to acclimation by facilitating drought tolerant morphology. Recent results pinpoint the importance of cuticular structure in acclimation to drought stress at high water potential (ψ).

Histological and microarray analysis of the direct effect of water shortage alone or combined with heat on early grain development in wheat (Triticum aestivum)

Based on the in silico analysis of the representation of expressed sequence tags (ESTs) in wheat grain-related cDNA libraries, a specific 15k oligonucleotide microarray has been developed in order to monitor environmental stress-dependent gene expression changes in the wheat caryopses. Using this array, the effect of water withdrawal, with and without additional heat stress, has been investigated during the first five days of kernel development on two wheat cultivars differing in their drought sensitivity. Water shortage affected (more than twofold change) the expression of only 0.5% of the investigated genes. A parallel heat treatment increased the ratio of responding genes to 5-7% because of the temperature stress and/or the increased water deficit because of enhanced evaporation. It could be established that the two cultivars, differing in their long-term adaptation capabilities to drought, responded to the short and direct stress treatments on the same way. In response to the combined drought and heat treatment, the coordinately altered expression of genes coding for storage proteins, enzymes involved in sugar/starch metabolism, histone proteins, heat shock proteins, proteases, tonoplast aquaporins as well as several transcription factors has been observed. These gene expression changes were in agreement with histological data that demonstrated the accelerated development of the embryo as well as the endosperm.

Isolated microspore cultures of a Hungarian durum wheat ( Triticum turgidum L.) cultivar, Martondur 1

A number of sporophytically induced microspores and embryo-like structures (ELS) were obtained from isolated microspore cultures of durum wheat ( Triticum turgidum L. cv. Martondur 1). Various pre-treatments were screened, involving spike treatment at 4°C for 2, 7 or 14 days; anther treatment in 0.4 M mannitol containing macroelements at 33°C for 3 days, and various combinations of these. The frequency of embryogenic (star-like) microspores and the number of ELS showed a very high positive correlation in the cultures. Starvation at high temperature was necessary to achieve a reasonable frequency of microspore embryogenesis. The best results were achieved when starvation at high temperature was combined with no or short (2-day) cold treatment (212±77 and 203±34 ELS/100 anthers, respectively). However, the ELS failed to regenerate; only a few of them produced poorly-developed albino shoots. The present work could be a promising starting point for the production of doubled haploid durum wheat plants in Hungary via isolated microspore culture.

Current-induced two-level fluctuations in pseudo-spin-valve (Co/Cu/Co) nanostructures

Two-level fluctuations of the magnetization state of pseudo-spin-valve pillars Co(10 nm)/Cu(10 nm)/Co(30 nm) embedded in electrodeposited nanowires ( approximately 40 nm in diameter, 6000 nm in length) are triggered by spin-polarized currents of 10(7) A/cm(2) at room temperature. The statistical properties of the residence times in the parallel and antiparallel magnetization states reveal two effects with qualitatively different dependences on current intensity. The current appears to have the effect of a field determined as the bias field required to equalize these times. The bias field changes sign when the current polarity is reversed. At this field, the effect of a current density of 10(7) A/cm(2) is to lower the mean time for switching down to the microsecond range. This effect is independent of the sign of the current and is interpreted in terms of an effective temperature for the magnetization.

A novel, selective synthetic acetamide containing culture medium for isolating Pseudomonas aeruginosa from milk

A selective synthetic medium has been developed both in liquid (Z-broth) and solid (Z-agar) forms for selective isolation of Pseudomonas aeruginosa from foods. The simple, easy to prepare peptone-free synthetic medium contained acetamide that is metabolized to ammonia and acetic acid providing nitrogen and carbon supply. The medium contained no inhibitors. Selectivity of the liquid medium was tested by inoculation of pure cultures of different bacteria belonging to the groups Bacillus, Pseudomonas, Enterobacteriaceae and Staphylococcus. It was found that the selectivity of the medium was complete for the examined range of bacteria. However, a similar result was obtained when nitrofurantoin broth was used. Applicability of the synthetic agar medium was also tested by a nation-wide inter-laboratory test using two milk samples containing 10(3)/ml (sample I) and 10(5)/ml (sample II) Pseudomonas aeruginosa. According to this test, no microbiologically relevant differences were found between the results obtained by Z-agar and cetrimide-agar a frequently used selective agar in case of sample II. However, a relevant and statistically significant difference was found in the results of sample I in favour of the Z-agar, that could indicate the presence of a low number of bacteria. Concerning repeatability and reproducibility, Z-agar proved to be superior to cetrimide agar.

[Prenatal ultrasonic diagnosis of cleft lips and palates]

The purpose of this communication is to demonstrate the possibility of prenatal diagnosis of cleft lips and palates by routine ultrasound screening. As obstetrical ultrasound improves, anomalies of the fetal face can be diagnosed more and more frequently in utero. From 1991 to 1994 9 cases with cleft face syndrome were detected prenatally. In 8 cases the presence of cleft lip and palate was isolated. In one case the cleft lip and palate was associated with phocomelia. In cases with cleft palate the widening of nasal cavity was observed. In cases with bilateral cleft palate polyhydramnions were observed twice and undulating movements of the tongue were also seen.

The role of intestinal volatile fatty acids in the Salmonella shedding of pigs

Factors affecting colonization of the intestinal tract by salmonellas were studied in two pig herds. In herd H 18% of the faecal samples taken from live pigs and 30% of the colon content samples collected at slaughter contained salmonellas. In contrast, the 50 faecal samples taken from pigs of herd L were negative and only 2% of the colon contents collected at the yielded salmonellas. An antibacterial effect inhibiting salmonella multiplication was demonstrable in vitro in colon contents from pigs of herd L. No such effect was found to exist in samples taken from pigs of herd H. The antibacterial effect is due to the non-dissociated volatile fatty acid (VFA) molecules present in the colon content. As the degree of VFA dissociation depends on the pH of the environment, at lower pH values (pH 6.1 +/- 0.2) of the colon contents from herd L the ratio of non-dissociated VFA molecules is higher and the resulting antibacterial effect is stronger than in samples from herd H (pH 7.1 +/- 0.3).