Gall inducer Dasineura sp. alters the polyphenol profile and antioxidant activity of Peumus boldus stems.

Peumus boldus, a tree native to Chile, is extensively used for medicinal purposes due to its richness in alkaloids and antioxidant polyphenols. A species of galling insect, Dasineura sp. induces structural and chemical changes on P. boldus stems while its galls are established and developed. Taking into account the antioxidant properties of P. boldus polyphenols, it would be expected that Dasineura sp. induces changes in the accumulation sites, chemical profile, and antioxidant activity of the P. boldus stem polyphenols, related to different reactive oxygen species (ROS) production levels during gall development. Dasineura sp. induces changes in the accumulation sites of total polyphenols, flavonols, and lignin, redirecting their accumulation toward the sites of greatest production of H2O2 and O2.-. Although changes in total polyphenol content would be expected, this did not vary significantly between non-galled and galled stems. However, the galling insect induced changes in the profile and concentration of soluble polyphenols, leading to the gall extracts' antioxidant capacity decreasing significantly during the maturation and senescence stages. Additionally, during the maturation stage, lignin deposition increases in the more peripheral gall tissues, which also contributes to ROS dissipation. The differences in the different gall developmental stages' antioxidant activity could be related to the identity and concentration of phenolic compounds in each gall extract, rather than to the total phenol content. Regardless of the mechanisms involved, the dissipation of the ROS generated by Dasineura sp. activity occurs, restoring the redox balance in galls and guaranteeing the success of the inducer.

Alterations induced by Colomerus vitis on the structural and physiological leaf features of two grape cultivars.

Vitis vinifera is cultivated worldwide for its high nutritional and commercial value. More than 60 grape cultivars are cultivated in Chile. Two of these, the país and the corinto cultivars, are the oldest known and widely used for the preparation of traditional homemade drinks and consumption as table grapes. These two grape cultivars are affected by Colomerus vitis, an eriophyid mite which establishes on their leaves and forms erinea, where the mite and its offspring obtain shelter and food. Although C. vitis has a cosmopolitan distribution, few studies of its impact on the structure and physiology of affected plants have been reported. Herein we aimed to evaluate the impact of C. vitis infection on the structural and physiological leaf performance of the two grape cultivars. The results showed tissue hyperplasia and cell hypertrophy in the epidermis, with an overproduction of trichomes and emergences in the abaxial epidermis in both cultivars. The anatomical changes were similar between the país and corinto cultivars, but they were proportionally greater in the país, where the area affected by the erinea were greater. No significant changes were detected in the photosynthetic pigment content; however, there was an increase in the total soluble sugars content in the erineum leaves of the país cultivar. Higher contents of anthocyanins and total phenols, as well as the presence of the pinocembrin in the corinto cultivar, which was less affected by C. vitis, could also indicate some resistance to mites' attack, which should be investigated in future studies.

Phenolic Antioxidant Protection in the Initial Growth of Cryptocarya alba: Two Different Responses against Two Invasive Fabaceae.

The allelophatic effect of the invasive Fabaceae, Ulex europaeus and Teline monspessulana, on the production of phenolic compounds in C. alba seedlings was investigated. It was expected that the oxidative stress caused by the allelochemicals released by both invaders would induce a differential response in the production of phenolic compounds in C. alba seedlings. These antioxidant mechanisms guaranteed C. alba plants' survival, even to the detriment of their initial growth. Cryptocarya alba seedlings were irrigated with T. monspessulana (TE) and U. europaeus (UE) extracts and water as a control. After eight months, morphometric variables were evaluated, and leaves were collected for histochemical analysis. The methanol extracts from treatments and control leaves were used for anthocyanin, phenol, and antioxidant activity quantifications. Both invasive species induced an inhibitory effect on the morphometric variables. Teline monspessulana induced leaf damage and increased the anthocyanin content by 4.9-fold, but did not affect the phenol content. Ulex europaeus induces root damage and a decrease in phenol content, but does not affect the anthocyanin content. Both Fabaceae extracts affected the profile and polyphenol concentration and consequently decreased the antioxidant capacity of C. alba leaves at low extract concentrations. Phenols, lignin, and ROS accumulate on C. alba leaves, but the histochemical reactions were less intense under UE. Although C. alba develops different antioxidant protection mechanisms against stress induced by UE and TE, its survival is guaranteed, even to the detriment of its initial growth.

Gall-inducing Eriophyes tiliae stimulates the metabolism of Tilia platyphyllos leaves towards oxidative protection.

Red galls have high levels of anthocyanins which perform different physiological functions, such as antioxidants and protection against UVB radiation. High levels of anthocyanins and other polyphenols have been associated with low photosynthetic pigment content. In environments with high levels of UVB radiation, it would thus be expected that red galls would have high anthocyanin and polyphenol levels and low photosynthetic pigment contents, enabling the gall with high antioxidant capacity compared to its host organ. The red galls induced by Eriophyes tiliae, and their host environment of Tilia platyphyllos leaves in the Mediterranean climate of Chile, were investigated in relation to their anatomy, histochemistry, pigment, sugar, protein, and polyphenol contents, and antioxidant capacity. The anthocyanin, sugars, and polyphenol contents and the antioxidant capacity were increased in galls. Photosynthetic pigment and protein contents were higher in non-galled leaves. The high levels of anthocyanin and total polyphenols increase the galls' antioxidant capacity in the high UV radiation environment of a Mediterranean climate. The establishment of E. tiliae induced redifferentiation of nutritive tissue, rich in sugars, proteins, and lipids, and an inner epidermis with trichomes and long emergences. E. tiliae galls' structural and metabolic features are probably enhanced towards mite nutrition and protection. The current results shed light on the role of anthocyanin in the antioxidant protection of plant galls in environments with high UV irradiance.

Numerical solution of a spatio-temporal predator-prey model with infected prey.

A spatio-temporal eco-epidemiological model is formulated by combining an available non-spatial model for predator-prey dynamics with infected prey [D. Greenhalgh and M. Haque, Math. Meth. Appl. Sci., 30 (2007), 911-929] with a spatio-temporal susceptible-infective (SI)-type epidemic model of pattern formation due to diffusion [G.-Q. Sun, Nonlinear Dynamics, 69 (2012), 1097-1104]. It is assumed that predators exclusively eat infected prey, in agreement with the hypothesis that the infection weakens the prey, making it available for predation otherwise we assume that the predator has essentially no access to healthy prey of the same species. Furthermore, the movement of predators is described by a non-local convolution of the density of infected prey as proposed in [R.M. Colombo and E. Rossi, Commun. Math. Sci., 13 (2015), 369-400]. The resulting convection-diffusion-reaction system of three partial differential equations for the densities of susceptible and infected prey and predators is solved by an efficient method that combines weighted essentially non-oscillatory (WENO) reconstructions and an implicit-explicit Runge-Kutta (IMEX-RK) method for time stepping. Numerical examples illustrate the formation of spatial patterns involving all three species.

Numerical solution of a spatio-temporal gender-structured model for hantavirus infection in rodents.

In this article we describe the transmission dynamics of hantavirus in rodents using a spatio-temporal susceptible-exposed-infective-recovered (SEIR) compartmental model that distinguishes between male and female subpopulations [L.J.S. Allen, R.K. McCormack and C.B. Jonsson, Bull. Math. Biol. 68 (2006), 511--524]. Both subpopulations are assumed to differ in their movement with respect to local variations in the densities of their own and the opposite gender group. Three alternative models for the movement of the male individuals are examined. In some cases the movement is not only directed by the gradient of a density (as in the standard diffusive case), but also by a non-local convolution of density values as proposed, in another context, in [R.M. Colombo and E. Rossi, Commun. Math. Sci., 13 (2015), 369--400]. An efficient numerical method for the resulting convection-diffusion-reaction system of partial differential equations is proposed. This method involves techniques of weighted essentially non-oscillatory (WENO) reconstructions in combination with implicit-explicit Runge-Kutta (IMEX-RK) methods for time stepping. The numerical results demonstrate significant differences in the spatio-temporal behavior predicted by the different models, which suggest future research directions.