SYNAPTONEMAL COMPLEX KARYOTYPING OF TRADESCANTIA ZYGOTENE NUCLEI

Zygotene synaptonemal complex karyotyping of five strains of diploid Tradescantia was carried out using the whole mount spreading technique. The presence of pairing partner switches in the zygotene preparations suggested the presence of chromosomal structural heterozygosity. Metaphase and Anaphase I analysis confirmed the presence of heterozygous translocations and inversions. Two plants analyzed had large centric fragments. In a nucleus from one, the fragments were completely synapsed; in a nucleus from the other, there was very little synapsis. Difficulties arose in adapting the whole mount spreading technique to the long Tradescantia chromosomes. Variability was encountered in both the contrast obtained and in the degree to which the chromosomal axes were stretched. Possible sources of the variability are discussed.     

Fourier Power Spectrum Characteristics of Face Photographs: Attractiveness Perception Depends on Low-Level Image Properties

We investigated whether low-level processed image properties that are shared by natural scenes and artworks – but not veridical face photographs – affect the perception of facial attractiveness and age. Specifically, we considered the slope of the radially averaged Fourier power spectrum in a log-log plot. This slope is a measure of the distribution of special frequency power in an image. Images of natural scenes and artworks possess – compared to face images – a relatively shallow slope (i.e., increased high spatial frequency power). Since aesthetic perception might be based on the efficient processing of images with natural scene statistics, we assumed that the perception of facial attractiveness might also be affected by these properties. We calculated Fourier slope and other beauty-associated measurements in face images and correlated them with ratings of attractiveness and age of the depicted persons (Study 1). We found that Fourier slope – in contrast to the other tested image properties – did not predict attractiveness ratings when we controlled for age. In Study 2A, we overlaid face images with random-phase patterns with different statistics. Patterns with a slope similar to those in natural scenes and artworks resulted in lower attractiveness and higher age ratings. In Studies 2B and 2C, we directly manipulated the Fourier slope of face images and found that images with shallower slopes were rated as more attractive. Additionally, attractiveness of unaltered faces was affected by the Fourier slope of a random-phase background (Study 3). Faces in front of backgrounds with statistics similar to natural scenes and faces were rated as more attractive. We conclude that facial attractiveness ratings are affected by specific image properties. An explanation might be the efficient coding hypothesis.     

Frequency of inversions affects senescence phenology of Acer pseudoplatanus and Fagus sylvatica

In mountainous regions, inversion situations with cold-air pools in the valleys occur frequently, especially in fall and winter. With the accumulation of inversion days, trees in lower elevations experience lower temperature sums than those in middle elevations. In a two-year observational study, deciduous trees, such as Acer pseudoplatanus and Fagus sylvatica, on altitudinal transects responded in their fall leaf senescence phenology. Phenological phases were advanced and senescence duration was shortened by the cold temperatures in the valley. This effect was more distinct for late phases than for early phases since they experienced more inversion days. The higher the inversion frequency, the stronger the signal was. Acer pseudoplatanus proved to be more sensitive to cold temperatures compared to Fagus sylvatica. We conclude that cold-air pools have a considerable impact on the vegetation period of deciduous trees. Considering this effect, trees in the mid hillside slopes gain advantages compared to lower elevations. Our findings will help to improve knowledge about ecological drivers and responses in mountainous forest ecosystems.     

Arabidopsis MPK6 is involved in cell division plane control during early root development,and localizes to the pre‐prophase band,phragmoplast, trans‐Golgi network and plasma membrane

The proper spatial and temporal expression and localization of mitogen‐activated protein kinases (MAPKs) is essential for developmental and cellular signalling in all eukaryotes. Here, we analysed expression, subcellular localization and function of MPK6 in roots of Arabidopsis thaliana using wild‐type plants and three mpk6 knock‐out mutant lines. The MPK6 promoter showed two expression maxima in the most apical part of the root meristem and in the root transition zone. This expression pattern was highly consistent with ‘no root’ and ‘short root’ phenotypes, as well as with ectopic cell divisions and aberrant cell division planes, resulting in disordered cell files in the roots of these mpk6 knock‐out mutants. In dividing root cells, MPK6 was localized on the subcellular level to distinct fine spots in the pre‐prophase band and phragmoplast, representing the two most important cytoskeletal structures controlling the cell division plane. By combining subcellular fractionation and microscopic in situ and in vivo co‐localization methods, MPK6 was localized to the plasma membrane (PM) and the trans‐Golgi network (TGN). In summary, these data suggest that MPK6 localizing to mitotic microtubules, secretory TGN vesicles and the PM is involved in cell division plane control and root development in Arabidopsis.     

Innervation pattern of suboesophageal ventral unpaired median neurones in the honeybee brain

In honeybees (Apis mellifera), the biogenic amine octopamine has been shown to play a role in associative and non-associative learning and in the division of labour in the hive. Immunohistochemical studies indicate that the ventral unpaired median (VUM) neurones in the suboesophageal ganglion (SOG) are putatively octopaminergic and therefore might be involved in the octopaminergic modulation of behaviour. In contrast to our knowledge about the behavioural effects of octopamine, only one neurone (VUMmx1) has been related to a behavioural effect (the reward function during olfactory learning). In this study, we have investigated suboesophageal VUM neurones with fluorescent dye-tracing techniques and intracellular recordings combined with intracellular staining. Ten different VUM neurones have been found including six VUM neurones innervating neuropile regions of the brain and the SOG exclusively (central VUM neurones) and four VUM neurones with axons in peripheral nerves (peripheral VUM neurones). The central VUM neurones innervate the antennal lobes, the protocerebral lobes (including the lateral horn) and the mushroom body calyces. Of these, a novel mandibular VUM neurone, VUMmd1, exhibits the same branching pattern in the brain as VUMmx1 and responds to sucrose and odours in a similar way. The peripheral VUM neurones innervate the antennal and the mandibular nerves. In addition, we describe one labial unpaired median neurone with a dorsal cell body, DUMlb1. The possible homology between the honeybee VUM neurones and the unpaired median neurones in other insects is discussed. This work was supported by the DFG ME 365/24-2.     

Mutations in autism susceptibility candidate 2 (AUTS2) in patients with mental retardation

We report on three unrelated mentally disabled patients, each carrying a de novo balanced translocation that truncates the autism susceptibility candidate 2 (AUTS2) gene at 7q11.2. One of our patients shows relatively mild mental retardation; the other two display more profound disorders. One patient is also physically disabled, exhibiting urogenital and limb malformations in addition to severe mental retardation. The function of AUTS2 is presently unknown, but it has been shown to be disrupted in monozygotic twins with autism and mental retardation, both carrying a translocation t(7;20)(q11.2;p11.2) (de la Barra et al. in Rev Chil Pediatr 57:549–554, 1986; Sultana et al. in Genomics 80:129–134, 2002). Given the overlap of this autism/mental retardation (MR) phenotype and the MR-associated disorders in our patients, together with the fact that mapping of the additional autosomal breakpoints involved did not disclose obvious candidate disease genes, we ascertain with this study that AUTS2 mutations are clearly linked to autosomal dominant mental retardation.     

Specialization, constraints, and conflicting interests in mutualistic networks

The topology of ecological interaction webs holds important information for theories of coevolution, biodiversity, and ecosystem stability . However, most previous network analyses solely counted the number of links and ignored variation in link strength. Because of this crude resolution, results vary with scale and sampling intensity, thus hampering a comparison of network patterns at different levels . We applied a recently developed quantitative and scale-independent analysis based on information theory to 51 mutualistic plant-animal networks, with interaction frequency as measure of link strength. Most networks were highly structured, deviating significantly from random associations. The degree of specialization was independent of network size. Pollination webs were significantly more specialized than seed-dispersal webs, and obligate symbiotic ant-plant mutualisms were more specialized than nectar-mediated facultative ones. Across networks, the average specialization of animal and plants was correlated, but is constrained by the ratio of plant to animal species involved. In pollination webs, rarely visited plants were on average more specialized than frequently attended ones, whereas specialization of pollinators was positively correlated with their interaction frequency. We conclude that quantitative specialization in ecological communities mirrors evolutionary trade-offs and constraints of web architecture. This approach can be easily expanded to other types of biological interactions.