Isolation Conditions for High Yields of Protoplasts from Laminaria saccharina and L. digitata (Phaeophyceae)

In an investigation of the main factors determining protoplastyield in Laminaria saccharina and L. digitata, protoplasts wereisolated from epidermal, cortical and medullary cells of vegetativethallus by incubation with commercial cellulases, crude andpurified mannuronate lyases and purified guluronate lyases.Treatment of the tissue with the calcium chelator EGTA beforeenzymatic digestion greatly increased the protoplast yield.Preplasmolysis was also necessary to obtain large numbers ofhealthy protoplasts and this was most effective when carriedout during chelation with EGTA. Purification of the mannuronatelyases by ion exchange chromatography reduced the toxicity ofthe crude enzyme preparation. The activities of the wall degradingenzymes were differentially influenced by pH and the optimumfor alginate-lyase activity (8.0) was higher than that for cellulaseactivity (<6.0). Protoplast yield decreased linearly withincreasing pH in the enzyme medium over the range tested (6.0–8.0),and this suggests that cellulases are more critical to walldigestion than alginate-lyases. Ionic osmotica gave improvedyields compared with sugar alcohols or sugars. Increasing thecalcium concentration of the enzyme medium brought about anexponential decrease in protoplast yield and wall digestionwas almost completely inhibited at concentrations exceeding8.0 mol m^–3. However, low levels of calcium (<2.0 molm^–3) were beneficial to protoplast viability. Yields of10⁷ to 10⁸ protoplasts g^–1 fr. wt. were consistently obtainedand 20% to 30% of these regenerated new cell walls within 1–2d of culture. Key words: Laminaria protoplasts, cell wall, alginate-lyases     

Diversity patterns amongst herbivorous dinosaurs and plants during the Cretaceous: implications for hypotheses of dinosaur/angiosperm co‐evolution

Abstract Palaeobiologists frequently attempt to identify examples of co‐evolutionary interactions over extended geological timescales. These hypotheses are often intuitively appealing, as co‐evolution is so prevalent in extant ecosystems, and are easy to formulate; however, they are much more difficult to test than their modern analogues. Among the more intriguing deep time co‐evolutionary scenarios are those that relate changes in Cretaceous dinosaur faunas to the primary radiation of flowering plants. Demonstration of temporal congruence between the diversifications of co‐evolving groups is necessary to establish whether co‐evolution could have occurred in such cases, but is insufficient to prove whether it actually did take place. Diversity patterns do, however, provide a means for falsifying such hypotheses. We have compiled a new database of Cretaceous dinosaur and plant distributions from information in the primary literature. This is used as the basis for plotting taxonomic diversity and occurrence curves for herbivorous dinosaurs (Sauropodomorpha, Stegosauria, Ankylosauria, Ornithopoda, Ceratopsia, Pachycephalosauria and herbivorous theropods) and major groups of plants (angiosperms, Bennettitales, cycads, cycadophytes, conifers, Filicales and Ginkgoales) that co‐occur in dinosaur‐bearing formations. Pairwise statistical comparisons were made between various floral and faunal groups to test for any significant similarities in the shapes of their diversity curves through time. We show that, with one possible exception, diversity patterns for major groups of herbivorous dinosaurs are not positively correlated with angiosperm diversity. In other words, at the level of major clades, there is no support for any diffuse co‐evolutionary relationship between herbivorous dinosaurs and flowering plants. The diversification of Late Cretaceous pachycephalosaurs (excluding the problematic taxon Stenopelix) shows a positive correlation, but this might be spuriously related to poor sampling in the Turonian–Santonian interval. Stegosauria shows a significant negative correlation with flowering plants and a significant positive correlation with the nonflowering cycadophytes (cycads, Bennettitales). This interesting pattern is worthy of further investigation, and it reflects the decline of both stegosaurs and cycadophytes during the Early Cretaceous.     

Changes in sperm tail development associated with Y chromosome meiotic drive leading to an excess of males in the medfly Ceratitis capitata (Diptera: Tephritidae)

The Mediterranean fruit fly Ceratitis capitata (Wied.) normally produces the sexes in equal ratio but strains carrying the Y chromosome meiotic drive MP (male‐producing) factor show an excess of males. This is associated with a loss of sperm, and abnormal sperm structure in terms of multiple axonemes, atypical numbers of mitochondrial derivatives, and sometimes an incorrect initial orientation of paracrystalline bodies to the axoneme. Sperms are bundled together within spermatocysts, and those with depleted content and abnormalities occur in the same MP testes as normal spermatocysts. The maximum number of sperms per cyst in control strains was 256, each with a single axoneme originating from a single centriole (kinetosome). The maximum per cyst in MP strains was also 256 but MP cysts contained up to 300 axonemes, providing evidence of multiplication of centrioles. The structural changes in MP sperm are discussed in relation to similar abnormalities reported in the mosquito Aedes aegypti inheriting the Y chromosome meiotic drive haplotype MD. The evolutionary significance of this phenomenon is considered. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 351–359.     

What makes a good psychiatrist? A survey of clinical tutors responsible for psychiatric training in the UK and Eire

The characteristics of a good psychiatrist practising in the UK health services have been described in policy but not in practice. We set out to determine what key characteristics are required for an individual to be identified as a good psychiatrist to become a member of the Royal College of Psychiatrists. A postal survey of all clinical tutors responsible for psychiatric training in the UK and Eire was carried out. These tutors are approved by the Royal College of Psychiatrists. 113 tutors responded (out of 163, 69.3% return). The most important identified characteristic was overall competency in diagnosis, management and investigations (98%) and the least desirable was ability to appraise staff (13%). With recent changes in training and assessment in the UK, further surveys of this kind are indicated to understand the trainers’ views, and should be extended also to trainees     

Resistance of potatoes transgenic for a cry1Ac9 gene, to Phthorimaea operculella (Lepidoptera: Gelechiidae) over field seasons and between plant organs

Stable performance of insect‐resistant transgenic plants across field seasons and between plant organs damaged by the insect pest is critical for management of this resistance in the field. To evaluate this, potato (Solanum tuberosum) lines transgenic for a cry1Ac9 gene with resistance to potato tuber moth (Phthorimaea operculella) were established in the field during the southern hemisphere summers of 1997/98, 1998/99 and 1999/00 as small field plots, each of 10 plants. Replicate plots of the non‐transgenic parent cultivars (at least one for every three independently derived transgenic lines) were planted randomly throughout the trials. Field‐grown foliage was challenged with larvae in the laboratory and a growth index (GI) was calculated for recovered larvae from each transgenic and non‐transgenic potato line. Larval growth on young and mature leaves, and on newly harvested or stored tubers was also measured in the laboratory. Foliage from the transgenic lines inhibited larval growth in all seasons tested. For both control and transgenic lines, larvae had slightly lower GIs when reared on mature leaves compared with young leaves, although the correlation between mean GI for young and mature transgenic leaves was high (r = 0.97). The correlation between the mean GIs of larvae on newly harvested tubers and on those stored for 5 months was also high (r = 1.0). However, the GIs of larvae on newly harvested transgenic tubers were larger than on transgenic tubers stored for 5 months. The relative growth indices (RGI = mean GI/number days before final weighing) of larvae reared on newly harvested tubers from transgenic lines were generally higher than those from young transgenic foliage, while the RGIs of larvae reared on non‐transgenic tubers were slightly lower than those fed non‐transgenic foliage. The correlation between mean RGIs of larvae fed tubers or foliage was 0.62. The transgenic potato lines exhibited stable resistance to larvae across field seasons, between affected plant organs, and between plant organs of different ages.     

Growth and development of Avena fatua (Wild-oat) in the field

The growth and development of field-grown Avena fatua plants were studied for autumn and spring sowings in two consecutive years. The duration of various growth stages from sowing until anthesis was quantified in terms of thermal time (accumulated degree days) or photothermal time (degree days modified by photoperiod). Base temperatures and photoperiods for developmental phases were estimated as those which minimised the coefficient of variation among sowing dates. Relationships were derived between leaf emergence, canopy height, plant leaf area, and photothermal time. Stem extension and flowering occurred earlier in autumn-sown plants than spring-sown plants. Autumn-sown plants produced more leaves on the main stem, and had greater leaf area and above-ground biomass at anthesis than spring-sown plants.