The plant isoflavenoid genistein activates p53 and Chk2 in an ATM-dependent manner

Genistein is an isoflavenoid that is abundant in soy beans. Genistein has been reported to have a wide range of biological activities and to play a role in the diminished incidence of breast cancer in populations that consume a soy-rich diet. Genistein was originally identified as an inhibitor of tyrosine kinases; however, it also inhibits topoisomerase II by stabilizing the covalent DNA cleavage complex, an event predicted to cause DNA damage. The topoisomerase II inhibitor etoposide acts in a similar manner. Here we show that genistein induces the up-regulation of p53 protein, phosphorylation of p53 at serine 15, activation of the sequence-specific DNA binding properties of p53, and phosphorylation of the hCds1/Chk2 protein kinase at threonine 68. Phosphorylation and activation of p53 and phosphorylation of Chk2 were not observed in ATM-deficient cells. In contrast, the topoisomerase II inhibitor etoposide induced phosphorylation of p53 and Chk2 in ATM-positive and ATM-deficient cells. In addition, genistein-treated ATM-deficient cells were significantly more susceptible to genistein-induced killing than were ATM-positive cells. Together our data suggest that ATM is required for activation of a DNA damage-induced pathway that activates p53 and Chk2 in response to genistein.

'Neighbourhood' size, dispersal and density estimates in the prickly forest skink (Gnypetoscincus queenslandiae) using individual genetic and demographic methods

Dispersal, or the amount of dispersion between an individual's birthplace and that of its offspring, is of great importance in population biology, behavioural ecology and conservation, however, obtaining direct estimates from field data on natural populations can be problematic. The prickly forest skink, Gnypetoscincus queenslandiae, is a rainforest endemic skink from the wet tropics of Australia. Because of its log-dwelling habits and lack of definite nesting sites, a demographic estimate of dispersal distance is difficult to obtain. Neighbourhood size, defined as 4 piD sigma (2) (where D is the population density and sigma (2) the mean axial squared parent-offspring dispersal rate), dispersal and density were estimated directly and indirectly for this species using mark-recapture and microsatellite data, respectively, on lizards captured at a local geographical scale of 3 ha. Mark-recapture data gave a dispersal rate of 843 m(2)/generation (assuming a generation time of 6.5 years), a time-scaled density of 13 635 individuals * generation/km(2) and, hence, a neighbourhood size of 144 individuals. A genetic method based on the multilocus (10 loci) microsatellite genotypes of individuals and their geographical location indicated that there is a significant isolation by distance pattern, and gave a neighbourhood size of 69 individuals, with a 95% confidence interval between 48 and 184. This translates into a dispersal rate of 404 m(2)/generation when using the mark-recapture density estimation, or an estimate of time-scaled population density of 6520 individuals * generation/km(2) when using the mark-recapture dispersal rate estimate. The relationship between the two categories of neighbourhood size, dispersal and density estimates and reasons for any disparities are discussed.

Host plant specificity in several species of generalist mite predators

1. Species in the genus Neoseiulus are considered to be generalist predators. with some species used in biological control programmes against phytophagous mites and insects. 2. A general survey of Neoseiulus species in inland Australia indicated that different species are associated with particular tree species. This pattern of host plant use was investigated for four Neoseiulus species (N. buxeus, N. cappari, N. brigarinus, N. eremitus) by means of a sampling programme through time and across space. 3. Each species of Neoseiulus was collected entirely or mostly from one species of tree: little or no overlap was detected despite the tree species growing in well-mixed stands. Host plant specificity thus appears to be strong in this genus. 4. Species in two other genera (Pholaseius and Australiseiulus), also considered to be predatory, showed a similar association with particular tree species. 5. The implications for the use of these predators in biological control are considerable. In particular, phytoseiid species with specific needs in terms of host plants may not be suitable for use as general purpose predators. Meeting the needs of phytoseiids through the modification of host plant attributes may be a step towards enhancing their efficacy as biological control agents.

Breeding for low input conditions and consequences for participatory plant breeding: Examples from tropical maize and wheat

Participatory plant breeding (PPB) has been suggested as an effective alternative to formal plant breeding (FPB) as a breeding strategy for achieving productivity gains under low input conditions. With genetic progress through PPB and FPB being determined by the same genetic variables, the likelihood of success of PPB approaches applied in low input target conditions was analyzed using two case studies from FPB that have resulted in significant productivity gains under low input conditions: (1) breeding tropical maize for low input conditions by CIMMYT, and (2) breeding of spring wheat for the highly variable low input rainfed farming systems in Australia. In both cases, genetic improvement was an outcome of long-term investment in a sustained research effort aimed at understanding the detail of the important environmental constraints to productivity and the plant requirements for improved adaptation to the identified constraints, followed up by the design and continued evaluation of efficient breeding strategies. The breeding strategies used differed between the two case studies but were consistent in their attention to the key determinants of response to selection: (1) ensuring adequate sources of genetic variation and high selection pressures for the important traits at all stages of the breeding program, (2) use of experimental procedures to achieve high levels of heritability in the breeding trials, and (3) testing strategies that achieved a high genetic correlation between performance of germplasm in the breeding trials and under on-farm conditions. The implications of the outcomes from these FPB case studies for realizing the positive motivations for adopting PPB strategies are discussed with particular reference for low input target environment conditions.

Mineral nutrition and plant morphogenesis

Plant morphogenesis in vitro can be achieved via two pathways, somatic embryogenesis or organogenesis. Relationships between the culture medium and explant leading to morphogenesis are complex and, despite extensive study, remain poorly understood. Primarily the composition and ratio of plant growth regulators are manipulated to optimize the, quality and numbers of embryos or organs initiated. However, many species and varieties do not respond to this classical approach and require further optimization by the variation of other chemical or physical factors. Mineral nutrients form a significant component of culture media but are often overlooked as possible morphogenic elicitors. The combination of minerals for a particular plant species and developmental pathway are usually determined by the empirical manipulation of one or a combination of existing published formulations. Often only one medium type is used for the duration of culture even though this formulation may not be optimal for the different stages of explant growth and development. Furthermore, mineral studies have often focused on growth rather than morphogenesis with very little known of the relationships between mineral uptake and morphogenesis. This article examines the present knowledge of the main effects that mineral nutrients have on plant morphogenesis in vitro. In particular, the dynamics of nitrogen, phosphorus, and calcium supply during development are discussed.

A general model for host plant selection in phytophagous insects

We develop a general theoretical framework for exploring the host plant selection behaviour of herbivorous insects. This model can be used to address a number of questions, including the evolution of specialists, generalists, preference hierarchies, and learning. We use our model to: (i) demonstrate the consequences of the extent to which the reproductive success of a foraging female is limited by the rate at which they find host plants (host limitation) or the number of eggs they carry (egg limitation); (ii) emphasize the different consequences of variation in behaviour before and after landing on (locating) a host (termed pre- and post-alighting, respectively); (iii) show that, in contrast to previous predictions, learning can be favoured in post-alighting behaviour-in particular, individuals can be selected to concentrate oviposition on an abundant low-quality host, whilst ignoring a rare higher-quality host; (iv) emphasize the importance of interactions between mechanisms in favouring specialization or learning. (C) 2002 Elsevier Science Ltd.

Constitutive expression of a phenylalanine ammonia-lyase gene from Stylosanthes humilis in transgenic tobacco leads to enhanced disease resistance but impaired plant growth

Transgenic tobacco plants expressing a phenylalanine ammonia-lyase cDNA (ShPAL), isolated from Stylosanthes humilis, under the control of the 35S promoter of the cauliflower mosaic virus were produced to test the effect of high level PAL expression on disease resistance. The transgenic plants showed up to eightfold PAL activity and were slowed in growth and flowering relative to non-transgenic controls which have segregated out the transgene. The expression of the ShPAL transgene and elevated PAL levels were correlated and stably inherited. In T-1 and T-2 tobacco plants with increased PAL activity, lesion expansion was significantly reduced by up to 55% on stems inoculated with the Oomycete pathogen Phytophthora parasitica pv. nicotianae, Lesion area was significantly reduced by up to 50% on leaves inoculated with the fungal pathogen Cercospora nicotianae. This study provides further evidence that PAL has a role in plant defence. (C) 2002 Elsevier Science Ltd. All rights reserved.

Dispersal strategies in Tasmanian native hens (Gallinula mortierii)

Individuals in cooperatively breeding species face a complex set of decisions when they reach reproductive maturity. During an 8-year study, we examined the histories of 214 Tasmanian native hens (Gallinula mortierii) from hatching to examine the strategies they used to acquire breeding positions and the reproductive success they experienced in those breeding positions. Two-thirds of young delayed dispersal from their natal groups for at least a year. Ecological constraints were a partial cause of delayed dispersal; high-quality territories were rare and remained occupied due to high adult survivorship. There were also clear benefits of philopatry. Individuals that inherited breeding positions on their natal territories gained better quality positions and experienced higher reproductive success in their first breeding attempts than did individuals who dispersed to other groups. Multivariate analyses showed that the method of acquisition of breeding positions was the only factor significantly related to the quality of the breeding positions attained. Males were more likely to inherit breeding positions in their natal groups than were females. The compositions of individuals' natal groups had no effect on whether they inherited breeding positions or dispersed. In contrast, the compositions of groups did appear to affect whether other birds dispersed into them, with birds rarely moving into groups that contained breeders or nonbreeders of the same sex as the potential dispersers. Short-term removals of breeders confirmed this finding. These results suggest that both ecological constraints and benefits of philopatry explain delayed dispersal in this species.

Molecular rates parallel diversification contrasts between carnivorous plant sister lineages

In the carnivorous plant family Lentibulariaceae, the bladderwort lineage (Utricularia and Genlisea) is substantially more species-rich and morphologically divergent than its sister lineage, the butterworts (Pinguicula). Bladderworts have a relaxed body plan that has permitted the evolution of terrestrial, epiphytic, and aquatic forms that capture prey in intricately designed suction bladders or corkscrew-shaped lobster-pot traps. In contrast, the flypaper-trapping butterworts maintain vegetative structures typical of angiosperms. We found that bladderwort genomes evolve significantly faster across seven loci (the trnL intron, the second trnL exon, the trnL-F intergenic spacer, the rps16 intron, rbcL, coxI, and 5.8S rDNA) representing all three genomic compartments. Generation time differences did not show a significant association. We relate these findings to the contested speciation rate hypothesis, which postulates a relationship between increased nucleotide substitution and increased cladogenesis. (C) 2002 The Willi Hennig Society.

Callus induction and plant regeneration from broccoli (Brassica oleracea var. italica) for transformation

We evaluated the efficiency of callus induction and plantlet regeneration from hypocotyl explants of broccoli (Brassica oleracea var. italica). The cultivars were ‘Marathon’, ‘Greenbelt’, and ‘Shogun’. Transformation success was not affected by the presence of tobacco feeder-cell layers on the culture media. The frequency of shoot regeneration was greater from 10-d-old hypocotyls than from 14-d-old hypocotyls. Both ‘Marathon’ and ‘Greenbelt’ had higher potentials for tissue regeneration than did ‘Shogun’. We found that for transformation selection, the optimum concentration was either 50 mg/L kanamycin or 100 mg/L genetkin.

Effectiveness of Three Seed-Trap Designs

Vegetation monitoring is essential to evaluate management and assess condition. However, methods that have been used cannot assess the viability of the community or provide indicators of future condition. Seed traps can be used to measure reproductive potential of a vegetation community via seed rain. This study evaluates three different seed-trap designs and compares their effectiveness in terms of the diversity and abundance of seed captured, the presence of seed-predating insects, cost, manufacturing ease and serviceability. Field trials were conducted in open, grassy woodlands in south-western and south-eastern Queensland. The results showed that the tall funnel-trap design was the least effective, while the wet wind trap and pitfall funnel trap proved more effective. On the basis of the results of this study, further investigations are recommended for testing trap performance in different vegetation communities, seed predation in relation to seed production and variation in seed production over time. Seed traps that monitor seed rain are potentially useful in assessing the health and viability of a vegetation community. Used in conjunction with other monitoring methods, they may offer valuable insights about the dynamics of entire communities and/or individual species, and therefore appropriate management strategies.

Simulation of insect movement with respect to plant architecture and morphogenesis

Developments in computer and three dimensional (3D) digitiser technologies have made it possible to keep track of the broad range of data required to simulate an insect moving around or over the highly heterogeneous habitat of a plant's surface. Properties of plant parts vary within a complex canopy architecture, and insect damage can induce further changes that affect an animal's movements, development and likelihood of survival. Models of plant architectural development based on Lindenmayer systems (L-systems) serve as dynamic platforms for simulation of insect movement, providing ail explicit model of the developing 3D structure of a plant as well as allowing physiological processes associated with plant growth and responses to damage to be described and Simulated. Simple examples of the use of the L-system formalism to model insect movement, operating Lit different spatial scales-from insects foraging on an individual plant to insects flying around plants in a field-are presented. Such models can be used to explore questions about the consequences of changes in environmental architecture and configuration on host finding, exploitation and its population consequences. In effect this model is a 'virtual ecosystem' laboratory to address local as well as landscape-level questions pertinent to plant-insect interactions, taking plant architecture into account. (C) 2002 Elsevier Science B.V. All rights reserved.