Behavioral and morphological responses of an insect herbivore to low nutrient quality are inhibited by plant chemical defenses

Animals have several strategies to contend with nutritionally poor diets, including compensatory consumption and enhanced food utilization efficiencies. Plants produce a diversity of defense compounds that affect the ability of herbivores to utilize these strategies in response to variation in food nutritional quality. Little is known, however, about effects of allelochemicals on herbivores utilizing integrated behavioral and morphological responses to reduced food quality. Our objectives were to (1) examine how variation in diet nutritional quality influences compensatory responses of a generalist insect herbivore, and (2) determine how plant defenses affect these processes. Gypsy moth (Lymantria dispar) larvae were administered one of nine combinations of diet having low, moderate, or high nutritional quality and 0, 2, or 4 % purified aspen (Populus tremuloides) salicinoids. We quantified larval growth, consumption, frass production, and biomass allocation to midgut tissue over a 4-day bioassay. In the absence of salicinoids, larvae compensated for reduced nutritional quality and maintained similar growth across all diets through increased consumption, altered midgut biomass allocation, and improved processing efficiencies. Dietary salicinoids reduced larval consumption, midgut biomass allocation, digestive efficiencies, and growth at all nutritional levels, but the effect size was more pronounced when larvae were fed nutritionally suboptimal diets. Our findings demonstrate that integrated behavioral and morphological compensatory responses to reduced food quality are affected by plant defenses, ultimately limiting compensatory responses and reducing larval performance

Stability of p53 Homologs

<div><p>Most proteins have not evolved for maximal thermal stability. Some are only marginally stable, as for example, the DNA-binding domains of p53 and its homologs, whose kinetic and thermodynamic stabilities are strongly correlated. Here, we applied high-throughput methods using a real-time PCR thermocycler to study the stability of several full-length orthologs and paralogs of the p53 family of transcription factors, which have diverse functions, ranging from tumour suppression to control of developmental processes. From isothermal denaturation fluorimetry and differential scanning fluorimetry, we found that full-length proteins showed the same correlation between kinetic and thermodynamic stability as their isolated DNA-binding domains. The stabilities of the full-length p53 orthologs were marginal and correlated with the temperature of their organism, paralleling the stability of the isolated DNA-binding domains. Additionally, the paralogs p63 and p73 were significantly more stable and long-lived than p53. The short half-life of p53 orthologs and the greater persistence of the paralogs may be biologically relevant.</p> </div