Variation in serotiny of three Banksia species along a climatic gradient

The degree of serotiny (i.e. the proportion of follicles remaining closed in each year's crop of cones since the last fire) was measured in Bank-sia attenuata, B. menziesii and B. prionotes at five sites along a climatic gradient extending 500 km north of Perth, Western Australia. The decrease in annual rainfall and increase in average temperature along the gradient paralleled a decrease in plant height and an increase in the degree of serotiny of all species. Extreme serotiny was recorded in the scrub-heath at the xeric end of the gradient whereas two species were essentially non-serotinous in the low woodland at the most mesic site. It is concluded that degree of serotiny is related to the fire characteristics of the site which depend on plant height. In xeric scrub-heath, the entire canopies of the Banksia spp. are consumed by fire which promotes massive release of seed. This facilitates recruitment in an otherwise unpredictable and unreliable seedbed. In mesic woodland, where cones rarely come into contact With flames, seeds are released spontaneously and site conditions are more conducive to recruitment in the inter-fire period.     

Flower colour change in Banksia ilicifolia: A signal for pollinators

Both birds and insects visit yellow flower heads of Banksia ilicifolia rather than those in the pink or red phases. Birds carry most pollen. Substantial nectar and pollen rewards are present only in the yellow phase. The timing of flower colour change also corresponds to a decline in viability of presented pollen and stigma receptivity. Colour change is age-dependent rather than pollinator-induced. Bird visits to yellow or red heads are essentially determined by the availability of nectar in each rather than differences in their visibility. Fruit set is negligible in the absence of pollinators but still < 1% in their presence. Banksia ilicifolia has the smallest heads and is the most localized of five co-occurring and partly co-flowering Banksia species. It is hypothesized that the restriction of flower colour change to B. ilicifolia increases the competitiveness of this species: bird visitors are directed to flower heads with abundant nectar, viable pollen and receptive stigmas, foraging and pollination efficiency thereby being enhanced without a marked reduction in long-distance attractiveness of the tree to potential pollinators.     

In Vitro Excystation of Cryptosporidium baileyi from Chickens1

Release of sporozoites from the oocysts of Cryptosporidium baileyi is described from Nomarski interference-contrast microscopy. Just prior to excystation, the four sporozoites became motile and rearranged themselves within the oocyst. The sporozoites were then rapidly expelled through an opening that formed in the oocyst wall, and the residuum was either released or retained within the oocyst. Excysted sporozoites were crescent shaped and measured 5.0–9.0 μm × 1.0–1.6 μm (x?= 6.8 × 1.1 μm). Excystation occurred when sodium taurocholate or a mixture of trypsin and sodium taurocholate was present in the incubation medium. High levels of excystation occurred at 37° or 40°C, but excystation did not occur at 4°C. The ability of biles from two avian and two mammalian hosts to produce excystation of C. baileyi was also studied. After a 2-h incubation at 40°C, the percentages of excystation were 69.5% in goat bile, 45.0% in pig bile, 33.0% in chicken bile, and 34.5% in turkey bile.     

Gas Content of Berries of the Australian Mistletoe Amyema preissii and the Effect of Maturity, Viscin, Temperature and Carbon Dioxide on Germination

Experiments conducted at light intensities equivalent to thosereaching the embryo through the intact pericarp showed that: (a) excised embryos from green berries would not germinate,but those from transitional and pink (mature) berries begangermination immediately; (b) the viscid layer neither stimulated nor inhibited germination; (c) there was 100% germination at 10–25°C but maximumelongation at 25–30 °C, with a minimum at 4 °Cand death at 40°C; (d) there was 100% germination at 1–5% CO₂ in air, butmaximum elongation at 1%. with>90% germination in air minusCO₂ and negligible at 20% CO₂, 16% O₂, 64% N₂|| or higher concentrationsof CO₂; (e) the average gas concentration in mature berries, as measuredby gas spectrometry, was 127% CO₂, 12% O₂, 61% N₂||. Minor fluctuationsin CO₂/O₂ content indicated limited photosynthesis as well asrespiration in both green and mature berries. The high CO₂ concentrationin the berry is sufficient in itself to explain the maintenanceof dormancy until the seed is excised by birds; (f) contrary to previous assumptions, most elongation of theembryo was due to growth of the cotyledons rather than of thehypocotyl or radicle.     

A high density physical map of chromosome 1BL supports evolutionary studies,map-based cloning and sequencing in wheat

Background

As for other major crops, achieving a complete wheat genome sequence is essential for the application of genomics to breeding new and improved varieties. To overcome the complexities of the large, highly repetitive and hexaploid wheat genome, the International Wheat Genome Sequencing Consortium established a chromosome-based strategy that was validated by the construction of the physical map of chromosome 3B. Here, we present improved strategies for the construction of highly integrated and ordered wheat physical maps, using chromosome 1BL as a template, and illustrate their potential for evolutionary studies and map-based cloning.

Results

Using a combination of novel high throughput marker assays and an assembly program, we developed a high quality physical map representing 93% of wheat chromosome 1BL, anchored and ordered with 5,489 markers including 1,161 genes. Analysis of the gene space organization and evolution revealed that gene distribution and conservation along the chromosome results from the superimposition of the ancestral grass and recent wheat evolutionary patterns, leading to a peak of synteny in the central part of the chromosome arm and an increased density of non-collinear genes towards the telomere. With a density of about 11 markers per Mb, the 1BL physical map provides 916 markers, including 193 genes, for fine mapping the 40 QTLs mapped on this chromosome.

Conclusions

Here, we demonstrate that high marker density physical maps can be developed in complex genomes such as wheat to accelerate map-based cloning, gain new insights into genome evolution, and provide a foundation for reference sequencing.     

Evaluation and classification of RING-finger domains encoded by the <Emphasis Type="Italic">Arabidopsis</Emphasis> genome

Background

In computational analysis, the RING-finger domain is one of the most frequently detected domains in the Arabidopsis proteome. In fact, it is more abundant in Arabidopsis than in other eukaryotic genomes. However, computational analysis might classify ambiguous domains of the closely related PHD and LIM motifs as RING domains by mistake. Thus, we set out to define an ordered set of Arabidopsis RING domains by evaluating predicted domains on the basis of recent structural data.

Results

Inspection of the proteome with a current InterPro release predicts 446 RING domains. We evaluated each detected domain and as a result eliminated 59 false positives. The remaining 387 domains were grouped by cluster analysis and according to their metal-ligand arrangement. We further defined novel patterns for additional computational analyses of the proteome. They were based on recent structural data that enable discrimination between the related RING, PHD and LIM domains. These patterns allow us to predict with different degrees of certainty whether a particular domain is indeed likely to form a RING finger.

Conclusions

In summary, 387 domains have a significant potential to form a RING-type cross-brace structure. Many of these RING domains overlap with predicted PHD domains; however, the RING domain signature mostly prevails. Thus, the abundance of PHD domains in Arabidopsis has been significantly overestimated. Cluster analysis of the RING domains defines groups of proteins, which frequently show significant similarity outside the RING domain. These groups document a common evolutionary origin of their members and potentially represent genes of overlapping functionality.

     

Limited direct effects of a massive wildfire on its sagebrush steppe bee community

1. Fire can affect bees directly through exposure to heat and smoke. Direct effects include mortality, injury, and displacement affecting at most two generations – adults and any immature progeny present during the fire. To study the direct effects of fire on bees, two criteria must be met. First, bees must be sampled soon after the fire event, before colonists arrive from outside the burn. Second, sampling locations must be far enough into the burned habitat to ensure that bees observed are survivors, and not foragers nesting outside the burn. 2. Bees were systematically sampled far inside (>7 km) and outside the burn perimeter immediately following a massive wildfire that burned primarily at night in sagebrush steppe habitat. Because adult females sleep in their nests, it was hypothesised that females of species with nests >10 cm underground would be safe from lethal heat, whereas females with shallow or above‐ground nests would be vulnerable. It was also hypothesised that fire would kill proportionately more males, as they typically sleep above ground. 3. Adult bees were present at all burned sample sites 14 and 21 days after the fire started. Many females were observed transporting pollen, indicative of active nest provisioning. Among the guild of bees surveyed at wild sunflowers (the only surviving flowering plant), fewer species were active within the burn. Guild composition was significantly altered, particularly by loss or depletion of several (but not all) sunflower specialists. Sex ratios did not shift, possibly due to surviving males aggregating in remaining patches of sunflowers.