Benzoxazinoids in Root Exudates of Maize Attract Pseudomonas putida to the Rhizosphere

Benzoxazinoids, such as 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA), are secondary metabolites in grasses. In addition to their function in plant defence against pests and diseases above-ground, benzoxazinoids (BXs) have also been implicated in defence below-ground, where they can exert allelochemical or antimicrobial activities. We have studied the impact of BXs on the interaction between maize and Pseudomonas putida KT2440, a competitive coloniser of the maize rhizosphere with plant-beneficial traits. Chromatographic analyses revealed that DIMBOA is the main BX compound in root exudates of maize. In vitro analysis of DIMBOA stability indicated that KT2440 tolerance of DIMBOA is based on metabolism-dependent breakdown of this BX compound. Transcriptome analysis of DIMBOA-exposed P. putida identified increased transcription of genes controlling benzoate catabolism and chemotaxis. Chemotaxis assays confirmed motility of P. putida towards DIMBOA. Moreover, colonisation essays in soil with Green Fluorescent Protein (GFP)-expressing P. putida showed that DIMBOA-producing roots of wild-type maize attract significantly higher numbers of P. putida cells than roots of the DIMBOA-deficient bx1 mutant. Our results demonstrate a central role for DIMBOA as a below-ground semiochemical for recruitment of plant-beneficial rhizobacteria during the relatively young and vulnerable growth stages of maize

Host Shifts from Lamiales to Brassicaceae in the Sawfly Genus Athalia

Plant chemistry can be a key driver of host shifts in herbivores. Several species in the sawfly genus Athalia are important economic pests on Brassicaceae, whereas other Athalia species are specialized on Lamiales. These host plants have glucosides in common, which are sequestered by larvae. To disentangle the possible direction of host shifts in this genus, we examined the sequestration specificity and feeding deterrence of iridoid glucosides (IGs) and glucosinolates (GSs) in larvae of five species which either naturally sequester IGs from their hosts within the Plantaginaceae (Lamiales) or GSs from Brassicaceae, respectively. Furthermore, adults were tested for feeding stimulation by a neo-clerodane diterpenoid which occurs in Lamiales. Larvae of the Plantaginaceae-feeders did not sequester artificially administered p-hydroxybenzylGS and were more deterred by GSs than Brassicaceae-feeders were by IGs. In contrast, larvae of Brassicaceae-feeders were able to sequester artificially administered catalpol (IG), which points to an ancestral association with Lamiales. In line with this finding, adults of all tested species were stimulated by the neo-clerodane diterpenoid. Finally, in a phylogenetic tree inferred from genetic marker sequences of 21 Athalia species, the sister species of all remaining 20 Athalia species also turned out to be a Lamiales-feeder. Fundamental physiological pre-adaptations, such as the establishment of a glucoside transporter, and mechanisms to circumvent activation of glucosides by glucosidases are therefore necessary prerequisites for successful host shifts between Lamiales and Brassicaceae

Public discourse on mental health and psychiatry: Representations in Swedish newspapers

Mass media plays a central role in shaping public discourse on health and illness. In order to examine media representations of mental health and expert knowledge in this field, two major Swedish daily newspapers from the year 2009 were qualitatively analysed. Drawing on the theory of social representations, the analysis focused on how issues concerning mental health and different perspectives are represented. The results show how the concept of mental illness is used in different and often taken-for-granted ways and how the distinction between normal and pathological is a central underlying question. Laypersons’ perspectives are supplemented by views of professionals in the newspapers, where signs of confidence and dependence on expert knowledge are juxtaposed with critique and expressions of distrust. The newspaper discourse thus has salient argumentative features and the way that conflicts are made explicit and issues concerning authoritative knowledge are addressed indicates ambivalence towards the authoritative role of expert knowledge concerning mental health. In this way, the newspapers provide a complex epistemic context for everyday sense-making that can be assumed to have implications for relations between laypersons and professionals in the field of mental health.</p

The limitations of locust preventive management faced with spatial uncertainty: exploration with a multi-agent model

International audienceBACKGROUND The spatial structure of locust outbreaks is a major aspect of preventive management that relies on where survey teams have to be sent if they are to react in time to any upsurge. The concentration of areas propitious to outbreaks has been documented for many species. Areas where preventive management fails to collect information because of insecurity or remoteness constitute other limits. We explored these conditions using a spatially explicit multi-agent model representing a preventive management system. We simulated areas where field teams had limited or no access and areas where the probability of initial outbreaks was concentrated in hotspots. RESULTS A strong effort by the budget holder to maintain funding over time might be cancelled out with 5% of a territory having limited access. The larger the area of no access, the worse the proportion of plague years. Multiple no access areas generated more plagues than only one no access area of an equivalent size because more fronts must be controlled. Concentrating outbreaks in hotspots increased the probability of plagues. One hotspot alone was easier to control than several same-sized hotspots. The period of the budget holder's cyclical behaviour between awareness and reduction in funding was longer with one hotspot than with several. CONCLUSION These results highlight the need to consider the spatial conditions and accessibility of locust species when planning the sustainability of management systems. Despite significant budgets to set in place a preventive management system, cyclical locust outbreaks may be related to these spatial conditions. (c) 2019 Society of Chemical Industr

Consequences of transferring three sorghum genes for secondary metabolite (cyanogenic glucoside) biosynthesis to grapevine hairy roots

The original publication can be found at www.springerlink.comA multigenic trait (biosynthesis of the secondary metabolite, dhurrin cyanogenic glucoside) was engineered de novo in grapevine (Vitis vinifera L.). This follows a recent report of transfer of the same trait to Arabidopsis (Arabidopsis thaliana) using three genetic sequences from sorghum (Sorghum bicolor): two cytochrome P450-encoding cDNAs (CYP79A1 and CYP71E1) and a UDPG-glucosyltransferase-encoding cDNA (sbHMNGT). Here we describe the two-step process involving whole plant transformation followed by hairy root transformation, which was used to transfer the same three sorghum sequences to grapevine. Transgenic grapevine hairy root lines that accumulated transcript from none, one (sbHMNGT), two (CYP79A1 and CYP71E1) or all three transgenes were recovered and characterisation of these lines provided information about the requirements for dhurrin biosynthesis in grapevine. Only lines that accumulated transcripts from all three transgenes had significantly elevated cyanide potential (up to the equivalent of about 100 mg HCN kg−1 fresh weight), and levels were highly variable. One dhurrin-positive line was tested and found to release cyanide upon maceration and can therefore be considered ‘cyanogenic’. In in vitro dual co-culture of this cyanogenic hairy root line or an acyanogenic line with the specialist root-sucking, gall-forming, aphid-like insect, grapevine phylloxera (Daktulosphaira vitifoliae, Fitch), there was no evidence for protection of the cyanogenic plant tissue from infestation by the insect. Consistently high levels of dhurrin accumulation may be required for this to occur. The possibility that endogenous grapevine gene expression is modulated in response to engineered dhurrin biosynthesis was investigated using microarray analysis of 1225 grapevine ESTs, but differences in patterns of gene expression associated with dhurrin-positive and dhurrin-negative phenotypes were not identified.T. K. Franks, K. S. Powell, S. Choimes, E. Marsh, P. Iocco, B. J. Sinclair, C. M. Ford and R. van Heeswijc