Witches' Broom Disease of Lime Contributes to Phytoplasma Epidemics and Attracts Insect Vectors.

An insect-transmitted phytoplasma causing Witches' Broom Disease of Lime (WBDL) is responsible for the drastic decline in lime production in several countries. However, it is unclear how WBDL phytoplasma (WBDLp) induces witches' broom symptoms and if these symptoms contribute to the spread of phytoplasma. Here we show that the gene encoding SAP11 of WBDLp (SAP11WBDL) is present in all WBDLp isolates collected from diseased trees. SAP11WBDL interacts with acid lime (Citrus aurantifolia) TCP transcription factors, specifically members of the TB1/CYC class that have a role in suppressing axillary branching in plants. Sampling of WBDLp-infected lime trees revealed that WBDLp titers and SAP11WBDL expression levels were higher in symptomatic leaves compared with asymptomatic sections of the same trees. Moreover, the witches' brooms were found to attract the vector leafhopper. Defense genes that have a role in plant defense responses to bacteria and insects are more downregulated in witches' brooms compared with asymptomatic sections of trees. These findings suggest that witches' broom-affected parts of the trees contribute to WBDL epidemics by supporting higher phytoplasma titers and attracting insect vectors.

Persistence and transgenerational effect of plant-mediated RNAi in aphids.

Plant-mediated RNA interference (RNAi) has been successfully used as a tool to study gene function in aphids. The persistence and transgenerational effects of plant-mediated RNAi in the green peach aphid (GPA) Myzus persicae were investigated, with a focus on three genes with different functions in the aphid. Rack1 is a key component of various cellular processes inside aphids, while candidate effector genes MpC002 and MpPIntO2 (Mp2) modulate aphid-plant interactions. The gene sequences and functions did not affect RNAi-mediated down-regulation and persistence levels in the aphids. Maximal reduction of gene expression was ~70% and this was achieved at between 4 d and 8 d of exposure of the aphids to double-stranded RNA (dsRNA)-producing transgenic Arabidopsis thaliana. Moreover, gene expression levels returned to wild-type levels within ~6 d after removal of the aphids from the transgenic plants, indicating that a continuous supply of dsRNA is required to maintain the RNAi effect. Target genes were also down-regulated in nymphs born from mothers exposed to dsRNA-producing transgenic plants, and the RNAi effect lasted twice as long (12-14 d) in these nymphs. Investigations of the impact of RNAi over three generations of aphids revealed that aphids reared on dsMpC002 transgenic plants experienced a 60% decline in aphid reproduction levels compared with a 40% decline of aphids reared on dsRack1 and dsMpPIntO2 plants. In a field setting, a reduction of the aphid reproduction by 40-60% would dramatically decrease aphid population growth, contributing to a substantial reduction in agricultural losses.

Least bad solutions to the 'drugs problem'.

This paper examines the current difficulties being faced in Australia by policy-makers attempting to regulate the non-medical use of illegal drugs, and it is suggested that the difficulties centre upon two aspects. First, existing prohibitions are unsuccessful, with use levels rising and, in some arenas (e.g. cocaine use in the USA), quite out of control. On the other hand, a move towards decriminalization or legalization is difficult because past propaganda has been so vehement that a change now apparently risks sending the wrong messages to young people. This dilemma means that there is no solution, including inertia, which is risk-free, nor is there one free of difficulties. It is thus relevant to think in terms of 'least bad' rather than 'best' when formulating a system to face these problems. The exploration of what this least bad solution might be begins with the examination of the prominent myths (such as 'the drug-free society', 'the evil pusher', 'the user as victim' and 'the young person as cultural dope') that hinder our reasoning. Secondly, by suggesting that, in a climate of increasing crime related to drugs, inability of prohibitions to control that use and escalating health risks attendant on use (including the AIDS problem), the central policy thrust must be harm reduction and damage minimization rather than illusory goals such as widespread abstinence. The paper concludes with a discussion of some relevant evidence on alternative options.

Social change and the control of psychotropic drugs-risk management, harm reduction and 'postmodernity'.

This paper argues that in order to understand the broad tide of change in drug control in recent times, we need to link these changes to a general understanding of social change. The paper sketches out how modern society arose and how it is giving way to the postmodern. Two themes are then developed. The first concerns the way that the state shrinks in postmodernity and links this to drug control, mentioning the example of random drug testing in the workplace as a good example of the change. It then moves to looking at the related shift in social control regimes from the 'corporal' regime of the premodern through the 'carceral' regime of the modern to population and risk management in the postmodern. It argues that in society in general there is a tension between carceral discipline and the amoral management of risk and that this is exhibited in drug control as a struggle between individual treatment and law enforcement on the one hand and 'harm reduction' on the other. This is illustrated by reference to a persistent tension within the NCADA enterprise.

The Canberra mental health survey: further analysis of the adult sample.

Secondary analysis of the Canberra Mental Health Survey (adult sample) extends the results of earlier analysis. New relationships between independent and dependent variables are revealed. Marital status previously not associated with mental health proves important when sex and socioeconomic status are controlled. Participation in organizations is strongly associated with social variables and mental health adjustment, suggesting explanations of mental health in relation to social support.