Cross-talk between high light stress and plant defence to the two-spotted spider mite in Arabidopsis thaliana

Little is known about how plants deal with arthropod herbivores under the fluctuating light intensity and spectra which occur in natural environments. Moreover, the role of simultaneous stress such as excess light (EL) in the regulation of plant responses to herbivores is poorly characterized. In the current study, we focused on a mite-herbivore, specifically, the two-spotted spider mite (TSSM), which is one of the major agricultural pests worldwide. Our results showed that TSSM-induced leaf damage (visualized by trypan blue staining) and oviposition rate (measured as daily female fecundity) decreased after EL pre-treatment in wild-type Arabidopsis plants, but the observed responses were not wavelength specific. Thus, we established that EL pre-treatment reduced Arabidopsis susceptibility to TSSM infestation. Due to the fact that a portion of EL energy is dissipated by plants as heat in the mechanism known as non-photochemical quenching (NPQ) of chlorophyll fluorescence, we tested an Arabidopsis npq4-1 mutant impaired in NPQ. We showed that npq4-1 plants are significantly less susceptible to TSSM feeding activity, and this result was not dependent on light pre-treatment. Therefore, our findings strongly support the role of light in plant defence against TSSM, pointing to a key role for a photo-protective mechanism such as NPQ in this regulation. We hypothesize that plants impaired in NPQ are constantly primed to mite attack, as this seems to be a universal evolutionarily conserved mechanism for herbivores

Mutation Analysis of NR5A1 Encoding Steroidogenic Factor 1 in 77 Patients with 46, XY Disorders of Sex Development (DSD) Including Hypospadias

BACKGROUND: Mutations of the NR5A1 gene encoding steroidogenic factor-1 have been reported in association with a wide spectrum of 46,XY DSD (Disorder of Sex Development) phenotypes including severe forms of hypospadias. METHODOLOGY/PRINCIPAL FINDINGS: We evaluated the frequency of NR5A1 gene mutations in a large series of patients presenting with 46,XY DSD and hypospadias. Based on their clinical presentation 77 patients were classified either as complete or partial gonadal dysgenesis (uterus seen at genitography and/or surgery, n = 11), ambiguous external genitalia without uterus (n = 33) or hypospadias (n = 33). We identified heterozygous NR5A1 mutations in 4 cases of ambiguous external genitalia without uterus (12.1%; p.Trp279Arg, pArg39Pro, c.390delG, c140_141insCACG) and a de novo missense mutation in one case with distal hypospadias (3%; p.Arg313Cys). Mutant proteins showed reduced transactivation activity and mutants p.Arg39Pro and p.Arg313Cys did not synergize with the GATA4 cofactor to stimulate reporter gene activity, although they retained their ability to physically interact with the GATA4 protein. CONCLUSIONS/SIGNIFICANCE: Mutations in NR5A1 were observed in 5/77 (6.5%) cases of 46,XY DSD including hypospadias. Excluding the cases of 46,XY gonadal dysgenesis the incidence of NR5A1 mutations was 5/66 (7.6%). An individual with isolated distal hypopadias carried a de novo heterozygous missense mutation, thus extending the range of phenotypes associated with NR5A1 mutations and suggesting that this group of patients should be screened for NR5A1 mutations

Influences of the Method of Introduction of Prey (tetranychus-urticae) and Predators (phytoseiulus-persimilis) On the Development of Plant Injury in Tomato Crops Under Glass

Two variants of the ''pest in first'' method of introduction of prey (Tetranychus urticae Koch) and predators (Phytoseiulus persimilis Athias-Henriot) on tomato crops were compared in a 80 M2 glasshouse. As opposed to the second crop, the first crop was protected against spider mites by early and multiple releases of predators ensuring high spatial coincidence between prey and predators. Plant injury gradually increased in crop 1, whereas it first peaked and then decreased to low values in crop 2. Mean plant injury was higher in the former crop, and so was the degree of spatial variability. The lack of persistent control in crop 1 indicates that the predators suppressed, but did not annihilate the spider mites in the prey patches where the predators were introduced. This enabled the spider mites to resurge shortly after their enemies had disappeared due to lack of food. In crop 2, the way the biological control was conducted permitted the predators to achieve so high densities that they could annihilate the spider mites in most patches. Not only did this synchronize the prey populations but it also prevented the pest from a fast recovery. Moreover, predators did not disappear and maintained spider mite populations at low levels

Phenology of Glandular Trichomes Related To Entrapment of Phytoseiulus-ersimilis A-h in the Glasshouse Tomato

High rates of mortality in populations of the predatory mite Phytoseiulus persimilis on tomato plants in spring and summer are due to entrapment by exudate from trichomes. Trichome phenology under glasshouse conditions was analyzed from March to November; their density, size, and amounts of trichome exudate fluctuated seasonally, increasing gradually in spring and decreasing in the autumn. A growth cabinet at 22-degrees-C and 65 % r.h. was used to measure the percentage of predators immobilized by trichome exudate within one hour on cut leaflet stalks from glasshouse plants. The rate of immobilization was correlated positively with the difference in temperature between the growth cabinet and the glasshouse when the temperature difference was more than +1 K. Otherwise, entrapment was correlated with trichome size and amount of exudate on stems

Asynchronous Populations of Phytoseiulus-persimilis Athias-henriot and Effective Control of Tetranychus-urticae Koch On Tomatoes Under Glass

A stable equilibrium between the predatory mite Phytoseiulus persimilis and the spider mite Tetranychus urticae in a tomato crop was attributed to asynchronous development of local populations of the predatory mites. This was achieved by introducing predatory mites into one half of the glasshouse at the beginning of the pest infestation period, while at the same time spraying acaricides in the other half. Thus, initial populations of both species of mites, and their subsequent development, were spatially different. Predator dispersal was responsible for maintaining the system and only 3,300 predators per 100 m2, combined with three acaricidal treatments applied to half the plants were necessary to protect the crop for a 30 week period. The system having been established, the mean number of spider mites per damaged leaflet was only 31 and the highest number of spider mite individuals per attacked leaflet was 160. In the last 14 weeks of the crop only 13% of the leaflets on the upper ten leaves showed feeding marks

Controlling Glasshouse Climate Influences the Interaction Between Tomato Glandular Trichome, Spider-mite and Predatory Mite

The effectiveness of the predatory mite Phytoseiulus persimilis in controlling spider mites on tomato crops depends on the climate which affects the balance between predator and prey. The effect of controlling glasshouse climatic conditions on the development of spider mite damage on tomato foliage was, therefore, examined. Climate was controlled by using a humidifying system and whitewash spray. Damage caused by spider mites was reduced, but the prey-predator system was more sensitive to unexpected changes in climate. After the whitewash was removed by thundery showers, more damage was caused by spider mites, there was a higher density of glandular trichomes on leaflets and a higher percentage of predators was stuck to leaflet trichomes than in the glasshouse control. This was attributed to increases in temperature and light intensity