The chemical signatures underlying host plant discrimination by aphids

The diversity of phytophagous insects is largely attributable to speciation involving shifts between host plants. These shifts are mediated by the close interaction between insects and plant metabolites. However, there has been limited progress in understanding the chemical signatures that underlie host preferences. We use the pea aphid (Acyrthosiphon pisum) to address this problem. Host-associated races of pea aphid discriminate between plant species in race-specific ways. We combined metabolomic profiling of multiple plant species with behavioural tests on two A. pisum races, to identify metabolites that explain variation in either acceptance or discrimination. Candidate compounds were identified using tandem mass spectrometry. Our results reveal a small number of compounds that explain a large proportion of variation in the differential acceptability of plants to A. pisum races. Two of these were identified as L-phenylalanine and L-tyrosine but it may be that metabolically-related compounds directly influence insect behaviour. The compounds implicated in differential acceptability were not related to the set correlated with general acceptability of plants to aphids, regardless of host race. Small changes in response to common metabolites may underlie host shifts. This study opens new opportunities for understanding the mechanistic basis of host discrimination and host shifts in insects

The injecting ‘event’: harm reduction beyond the human

Since the 1980s, the primary public health response to injecting drug use in the UK has been one of harm reduction. That is, reducing the harms associated with drug use without necessarily reducing consumption itself. Rooted in a post-Enlightenment idea of rationalism, interventions are premised on the rational individual who, given the right means, will choose to avoid harm. This lies in stark contrast to dominant addiction models that pervade popular images of the ‘out of control’ drug user, or worse, ‘junkie’. Whilst harm reduction has undoubtedly had vast successes, including challenging the otherwise pathologising and often stigmatising model of addiction, I argue that it has not gone far enough in addressing aspects of drug use that go beyond ‘rational’ and ‘human’ control. Drawing on my doctoral research with people who inject drugs, conducted in London, UK, this paper highlights the role of the injecting ‘event’, which far from being directed or controlled by a pre-defined individual or ‘body’ was composed by a fragile assemblage of bodies, human and nonhuman. Furthermore, in line with the ‘event’s’ heterogeneous and precarious make-up, multiple ways of ‘becoming’ through these events were possible. I look here at these ‘becomings’ as both stabilising and destabilising ways of being in the world, and argue that we need to pay closer attention to these events and what people are actually in the process of becoming in order to enact more accountable and ‘response-able’ harm reduction

Activity of Aspartate Aminotransferase and Alanine Aminotransferase Within Winter Triticale Seedlings Infested by Grain Aphid (Sitobion Avenae F.)

Amino acid level is well known indicator of plant resistance to aphids. Our earlier studies showed that grain aphid (Sitobion avenae F.) infestation caused changes in the activity of the enzymes connected with amino acid biosynthesis and the transformation to defensive secondary metabolites within triticale tissues. However, there are not data on the significance of aminotransferases in these processes. The aim of our study was the quantification of changes in the activity of aspartate aminotransferase (AspAT) and alanine aminotransferase (AlaAT) in winter triticale seedlings caused by the feeding of the grain aphid. The study results showed that aphid feeding caused an increase in AlaAT activity and a decrease in AspAT activity within tissues of the triticale. The induced mechanisms of the triticale resistance to the grain aphid are discussed

Changes in content and amino acid composition of soluble protein in winter triticale cultivars caused by grain aphid feeding

The obtained results showed that grain aphid (Sitobion avenae Fabr.) feeding caused an increase of the total protein content and a decrease of soluble protein level in the ears of both studied winter triticale cultivars (i.e. susceptible cultivar Grado and relatively resistant- Lasko). Moreover, the content of amino acids in soluble protein increased in Grado plants infested with the aphid, and reduced - in Lasko.Celem podjętych badań było określenie wpływu żerowania mszycy zbożowej na zawartość i skład aminokwasowy białka rozpuszczalnego wyizolowanego z kłosów dwóch odmian pszenżyta ozimego o zróżnicowanym stopniu odporności na tego szkodnika. W oparciu o uzyskane rezultaty stwierdzono, że żerowanie bezskrzydłych samic S. avenae wywołuje wzrost zawartości zarówno białka ogólnego jak i rozpuszczalnego w podatnej odmianie Grado. Natomiast w zasiedlonych przez mszyce roślinach względnie odpornej odmiany Lasko wzrastało stężenie białka ogólnego przy równoczesnym spadku poziomu białka rozpuszczalnego. Analiza składu aminokwasowego białka rozpuszczalnego wykazała, że pod wpływem żerowania S. avenae w pszenżycie Grado wzrasta zawartość aminokwasów egzogennych i endogennych, a w odmianie Lasko - obniża się. Otrzymane rezultaty dowiodły ponadto, że zmiany w zawartości i składzie aminokwasowym analizowanych frakcji białka uzależnione są w dużej mierze od czasu żerowania szkodnika

Reduktaza azotanowa siewek pszenzyta ozimego

Nitrite reductase (NiR) was extracted from seedlings of winter triticale cultivar Moreno in the form of homogenous protein fraction with molecular weight of about 61 kDa, characterised by maximum of absorption at 280 and 390 nm. Differences in specific activity of enzyme isolated from plants cultivated in different conditions (garden soil, Hoagland's diet) suggest that NiR may be induced by light and nitrate ions presence in arable medium

Activity of arginase within winter triticale seedlings attacked by grain aphid [Sitobion avenae F.]

Arginase (EC 3.5.3.1) catalyses biodegradation of L-arginine to L‑ornithine and urea. The aim of the study was to determine changes in arginase activity within seedlings of winter triticale caused by Sitobion avenae feeding. Obtained results showed an increase in the arginase activity within shoots of winter triticale seedlings susceptible Tornado cv and decrease in less susceptible Witon cv after 24 h of the grain aphid feeding. Further aphid feeding caused decrease in activity of the enzyme within shoots of the both studied cultivars and final induction after two weeks of feeding. In the roots of Tornado cv the enzyme activity decreased during the first week of the aphid feeding and slightly increased after two weeks. However, in analogous parts of the Witon cv seedlings settled by S. avenae an increase in arginase activity was observed after 24 h and decrease after one week was noticed. Importance of the arginase in interactions between the winter triticale and S. avenae is discussed

The influence of selected plant polyamines on feeding and survival of grain aphid (Sitobion avenae F.)

The influence of common plant polyamines on feeding behaviour and survival of grain aphid (Sitobion avenae F., Hemiptera: Aphididae) has been studied. Laboratory tests showed that wingless females of S. avenae assimilated higher quantities of food from triticale seedlings placed in 0.01% solutions of agmatine and cadaverine, and lower in case of spermidine and spermine. Increase in the polyamines concentrations up to 0.10% caused strong decrease in food assimilation, especially under the agmatine, cadaverine and putrescine treatment. Moreover, 0.10% concentration of the all analyzed polyamines decreased body mass and reduced survival of grain aphid wingless females. The 0.01% concentration of the polyamines were not affecting survival and body mass of S. avenae with exception of spermidine. Importance of the polyamines as potential natural biopesticides to the grain aphid is discussed