Phylogenetic and ecological analyses of soil and sporocarp DNA sequences reveal high diversity and strong habitat partitioning in the boreal ectomycorrhizal genus Russula (Russulales; Basidiomycota).

SUMMARY: *Although critical for the functioning of ecosystems, fungi are poorly known in high-latitude regions. Here, we provide the first genetic diversity assessment of one of the most diverse and abundant ectomycorrhizal genera in Alaska: Russula. *We analyzed internal transcribed spacer rDNA sequences from sporocarps and soil samples using phylogenetic methods, operational taxonomic unit (OTU) delimitations and ordinations to compare species composition in various types of boreal forest. *The genus Russula is highly diverse in Alaska, with at least 42 nonsingleton OTUs (soil) and 50 phylogroups (soil + sporocarp). Russula taxa showed strong habitat preference to one of the two major forest types in the sampled regions (black spruce and birch-aspen-white spruce), and some preference for soil horizon. *Our results show that the vast majority of Russula species are present in the soil samples, although some additional taxa are expected to be found with extended sampling. OTU diversity in black spruce forests was only one-third of the diversity observed in mixed upland forests. Our findings suggest that some of the diversity is niche based, especially along host and successional axes, because most OTUs predictably occurred in specific habitats, regardless of geographical location.

Beringian origins and cryptic speciation events in the fly agaric (Amanita muscaria).

Amanita muscaria sensu lato has a wide geographic distribution, occurring in Europe, Asia, Africa, Australia, New Zealand, and North, Central and South America. Previous phylogenetic work by others indicates three geographic clades (i.e. 'Eurasian', 'Eurasian-alpine' and 'North American' groups) within A. muscaria. However, the historical dispersal patterns of A. muscaria remained unclear. In our project, we collected specimens from arctic, boreal and humid temperate regions in Alaska, and generated DNA sequence data from the protein-coding beta-tubulin gene and the internal transcribed spacer (ITS) and large subunit (LSU) regions of the ribosomal DNA repeat. Homologous sequences from additional A. muscaria isolates were downloaded from GenBank. We conducted phylogenetic and nested clade analyses (NCA) to reveal the phylogeographic history of the species complex. Although phylogenetic analyses confirmed the existence of the three above-mentioned clades, representatives of all three groups were found to occur sympatrically in Alaska, suggesting that they represent cryptic phylogenetic species with partially overlapping geographic distributions rather than being allopatric populations. All phylogenetic species share at least two morphological varieties with other species, suggesting ancestral polymorphism in pileus and wart colour pre-dating their speciations. The ancestral population of A. muscaria likely evolved in the Siberian-Beringian region and underwent fragmentation as inferred from NCA and the coalescent analyses. The data suggest that these populations later evolved into species, expanded their range in North America and Eurasia. In addition to range expansions, populations of all three species remained in Beringia and adapted to the cooling climate.

Explaining math: gesturing lightens the load.

Why is it that people cannot keep their hands still when they talk? One reason may be that gesturing actually lightens cognitive load while a person is thinking of what to say. We asked adults and children to remember a list of letters or words while explaining how they solved a math problem. Both groups remembered significantly more items when they gestured during their math explanations than when they did not gesture. Gesturing appeared to save the speakers' cognitive resources on the explanation task, permitting the speakers to allocate more resources to the memory task. It is widely accepted that gesturing reflects a speaker's cognitive state, but our observations suggest that, by reducing cognitive load, gesturing may also play a role in shaping that state.

Effects of training on attention to acoustic cues.

Learning new phonetic categories in a second language may be thought of in terms of learning to focus one's attention on those parts of the acoustic-phonetic structure of speech that are phonologically relevant in any given context. As yet, however, no study has demonstrated directly that training can shift listeners' attention between acoustic cues given feedback about the linguistic phonetic category alone. In this paper we discuss the results of a training study in which subjects learned to shift their attention from one acoustic cue to another using only category-level identification as feedback. Results demonstrate that training redirects listeners' attention to acoustic cues and that this shift of attention generalizes to novel (untrained) phonetic contexts.

A physical map of 30,000 human genes.

A map of 30,181 human gene-based markers was assembled and integrated with the current genetic map by radiation hybrid mapping. The new gene map contains nearly twice as many genes as the previous release, includes most genes that encode proteins of known function, and is twofold to threefold more accurate than the previous version. A redesigned, more informative and functional World Wide Web site (www.ncbi.nlm.nih.gov/genemap) provides the mapping information and associated data and annotations. This resource constitutes an important infrastructure and tool for the study of complex genetic traits, the positional cloning of disease genes, the cross-referencing of mammalian genomes, and validated human transcribed sequences for large-scale studies of gene expression.

Hemispheric involvement in the perception of syntactic prosody is dynamically dependent on task demands.

The first aim of this study was to determine if there was a significant perceptual asymmetry for syntactic prosody and if it differed from the perceptual asymmetry for emotional prosody. The second aim of this study was to determine if the observed asymmetries were the product of task demands or stimulus features. Experiment 1 consisted of a Syntactic task and an Emotional task. In the Syntactic task, subjects identified Statement and Question prosody in dichotically presented sentences. In the Emotional task, subjects identified Angry and Sad prosody in dichotically presented sentences. There was a significant left ear advantage for the Emotional task and no significant ear advantage for the Syntactic task. In Experiment 2, subjects had to perform an Emotional prosody task with the syntactic Statement and Question prosody stimuli from Experiment 1. There was a significant left ear advantage, indicating that the perceptual asymmetry was determined by task demands and not stimulus features.

Characterization of short tandem repeats from thirty-one human telomeres.

Completion of genetic and physical maps requires markers from the ends (telomeres) of every human chromosome. We have searched for short tandem repeats (microsatellites) in cosmid and P1 clones and generated 661 sequence-tagged sites (STS) from the terminal 300 kb of 31 human chromosome ends. PCR assays were successfully designed for 58 microsatellites and mapped both genetically and on radiation hybrids (RHs) to confirm their telomeric location. Sequence analysis revealed marked variation in sequence composition, consistent with the hypothesis that even very highly GC-rich chromosome bands (the T bands) are not homogenous. The STSs that we have generated will be a necessary resource for the construction of physical maps of these complex regions of the genome.

A gene map of the human genome.

The human genome is thought to harbor 50,000 to 100,000 genes, of which about half have been sampled to date in the form of expressed sequence tags. An international consortium was organized to develop and map gene-based sequence tagged site markers on a set of two radiation hybrid panels and a yeast artificial chromosome library. More than 16,000 human genes have been mapped relative to a framework map that contains about 1000 polymorphic genetic markers. The gene map unifies the existing genetic and physical maps with the nucleotide and protein sequence databases in a fashion that should speed the discovery of genes underlying inherited human disease. The integrated resource is available through a site on the World Wide Web at http://www.ncbi.nlm.nih.gov/SCIENCE96/.

Cellular and molecular events in a newly organizing lateral root meristem.

Spontaneous or auxin-induced lateral root formation in radish and Arabidopis provides an efficient system in which to examine molecular and cellular events associated with the initiation of a new meristem. Subtracted cDNA libraries made at different times in lateral root initiation were used as a source of genes that are expressed differentially during this developmental process, and expression studies on a small gene family of ribosomal protein genes were conducted. From analysis of cell division patterns in pericycle cells the number of founder cells for lateral roots was established. By the use of in vitro growth assays lateral root formation was determined to be a two-stage process. First a primordium is formed, and subsequently a subset of primordial cells begins to function as the lateral root apical meristem. This mode of root development has implications for pattern formation in newly organizing organs.

Formation of lateral root meristems is a two-stage process.

In both radish and Arabidopsis, lateral root initiation involves a series of rapid divisions in pericycle cells located on the xylem radius of the root. In Arabidopsis, the number of pericycle cells that divide to form a primordium was estimated to be about 11. To determine the stage at which primordia are able to function as root meristems, primordia of different stages were excised and cultured without added hormones. Under these conditions, primordia that consist of 2 cell layers fail to develop while primordia that consist of at least 3-5 cell layers develop as lateral roots. We hypothesize that meristem formation is a two-step process involving an initial period during which a population of rapidly dividing, approximately isodiametric cells that constitutes the primordium is formed, and a subsequent stage during which meristem organization takes place within the primordium.

Processing interactions between segmental and suprasegmental information in native speakers of English and Mandarin Chinese.

The processing interactions between segmental and suprasegmental information in native speakers of English and Mandarin Chinese were investigated in a speeded classification task. Since in Chinese, unlike in English, tones convey lexically meaningful information, native speakers of these languages may process combinations of segmental and suprasegmental information differently. Subjects heard consonant-vowel syllables varying on a consonantal (segmental) dimension and either a Mandarin Chinese or constant-pitch (non-Mandarin) suprasegmental dimension. The English listeners showed mutual integrality with the Mandarin Chinese stimuli, but not the constant-pitch stimuli. The native Chinese listeners processed these dimensions with mutual integrality for both the Mandarin Chinese and the constant-pitch stimuli. These results were interpreted in terms of the linguistic function and the structure of suprasegmental information in Chinese and English. The results suggest that the way listeners perceive speech depends on the interaction between the structure of the signal and the processing strategies of the listener.

Transitions in learning: evidence for simultaneously activated strategies.

Children in transition with respect to a concept, when asked to explain that concept, often convey one strategy in speech and a different one in gesture. Are both strategies activated when that child solves problems instantiating the concept? While solving a math task, discordant children (who produced different strategies in gesture and speech on a pretest) and concordant children (who produced a single strategy) were given a word recall task. All of the children solved the math task incorrectly. However, if discordant children are activating two strategies to arrive at these incorrect solutions, they should expend more effort on this task than concordant children, and consequently have less capacity left over for word-recall and perform less well on it. This prediction was confirmed, suggesting that the transitional state is characterized by dual representations, both of which are activated when attempting to explain or solve a problem.

Initial evaluation of a hidden agenda method of teaching the interview.

A structured role-playing method of teaching the biopsychosocial interview using hidden agendas and videotape feedback was developed and evaluated. The teaching method significantly improved medical student interviewing skills as reflected by pre-post scores of 83 third-year students on the Facilitating Response Index. The teaching method is described in detail and recommendations for future research are presented.

Perceptual learning of synthetic speech produced by rule.

To examine the effects of stimulus structure and variability on perceptual learning, we compared transcription accuracy before and after training with synthetic speech produced by rule. Subjects were trained with either isolated words or fluent sentences of synthetic speech that were either novel stimuli or a fixed list of stimuli that was repeated. Subjects who were trained on the same stimuli every day improved as much as did the subjects who were given novel stimuli. In a second experiment, the size of the repeated stimulus set was reduced. Under these conditions, subjects trained with repeated stimuli did not generalize to novel stimuli as well as did subjects trained with novel stimuli. Our results suggest that perceptual learning depends on the degree to which the training stimuli characterize the underlying structure of the full stimulus set. Furthermore, we found that training with isolated words only increased the intelligibility of isolated words, although training with sentences increased the intelligibility of both isolated words and sentences.

Phonological priming in auditory word recognition.

Cohort theory, developed by Marslen-Wilson and Welsh (1978), proposes that a "cohort" of all the words beginning with a particular sound sequence will be activated during the initial stage of the word recognition process. We used a priming technique to test specific predictions regarding cohort activation in three experiments. In each experiment, subjects identified target words embedded in noise at different signal-to-noise ratios. The target words were either presented in isolation or preceded by a prime item that shared phonological information with the target. In Experiment 1, primes and targets were English words that shared zero, one, two, three, or all phonemes from the beginning of the word. In Experiment 2, nonword primes preceded word targets and shared initial phonemes. In Experiment 3, word primes and word targets shared phonemes from the end of a word. Evidence of reliable phonological priming was observed in all three experiments. The results of the first two experiments support the assumption of activation of lexical candidates based on word-initial information, as proposed in cohort theory. However, the results of the third experiment, which showed increased probability of correctly identifying targets that shared phonemes from the end of words, did not support the predictions derived from the theory. The findings are discussed in terms of current models of auditory word recognition and recent approaches to spoken-language understanding.

Amplification, enhanced expression and possible rearrangement of EGF receptor gene in primary human brain tumours of glial origin.

Epidermal growth factor (EGF), through interaction with specific cell surface receptors, generates a pleiotropic response that, by a poorly defined mechanism, can induce proliferation of target cells. Subversion of the EGF mitogenic signal through expression of a truncated receptor may be involved in transformation by the avian erythroblastosis virus (AEV) oncogene v-erb-B, suggesting that similar EGF receptor defects may be found in human neoplasias. Overexpression of EGF receptors has been reported on the epidermoid carcinoma cell line A431, in various primary brain tumours and in squamous carcinomas. In A431 cells the receptor gene is amplified. Here we show that 4 of 10 primary brain tumours of glial origin which express levels of EGF receptors that are higher than normal also have amplified EGF receptor genes. Amplified receptor genes were not detected in the other brain tumours examined. Further analysis of EGF receptor defects may show that such altered expression and amplification is a particular feature of certain human tumours.

Amplification and overexpression of the EGF receptor gene in primary human glioblastomas.

The expression of epidermal growth factor (EGF) receptor in brain tumours of glial origin was studied at the protein, mRNA and genomic levels. Four out of 10 glioblastomas that overexpress EGF receptor also have gene amplification. The amplified genes appear to be rearranged, generating an aberrant mRNA in at least one of these tumours. Such receptor defects may be relevant to tumorigenesis of human glioblastomas.