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Localized hormone fluxes and early haustorium development in the hemiparasitic plant Triphysaria versicolor
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Perhaps the most obvious phenotypes associated with chemical signaling between plants are manifested by parasitic species of Orobanchaceae. The development of haustoria, invasive root structures that allow hemiparasitic plants to transition from autotrophic to heterotrophic growth, is rapid, highly synchronous, and readily observed in vitro. Haustorium development is initiated in aseptic roots of the facultative parasite Triphysaria versicolor when exposed to phenolic molecules associated with host root exudates and rhizosphere bioactivity. Morphological features of early haustorium ontogeny include rapid cessation of root elongation, expansion, and differentiation of epidermal cells into haustorial hairs, and cortical cell expansion. These developmental processes were stimulated in aseptic T. versicolor seedlings by the application of exogenous phytohormones and inhibited by the application of hormone antagonists. Surgically dissected root tips formed haustoria if the root was exposed to haustorial-inducing factors prior to dissection. In contrast, root tips that were dissected prior to inducing-factor treatment were unable to form haustoria unless supplemented with indole-3-acetic acid. A transient transformation assay demonstrated that auxin and ethylene-responsive promoters were up-regulated when T. versicolor was exposed to either exogenous hormones or purified haustoria-inducing factors. These experiments demonstrate that localized auxin and ethylene accumulation are early events in haustorium development and that parasitic plants recruit established plant developmental mechanisms to realize parasite-specific functions. 相似文献
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Parasitic plant responses to host plant signals: a model for subterranean plant-plant interactions 总被引:1,自引:0,他引:1
Yoder JI 《Current opinion in plant biology》1999,2(1):65-70
The ability of plants to fulfill nutritional needs by parasitizing neighboring plants has originated several times in angiosperm evolution. Molecular tools are now being exploited to investigate the evolutionary origins of plant parasitism and to dissect the genetic mechanisms governing parasitic plant-host plant interactions. Investigating the nature of signal exchanges between parasitic plants and their hosts serves as a tractable system for understanding how plants in general communicate in the environment. This work should also lead to the development of novel strategies for minimizing the devastation caused by parasitic weeds in international agriculture. 相似文献
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Heritable variation in quinone-induced haustorium development in the parasitic plant Triphysaria
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We are using the facultative hemiparasite, Triphysaria, as a model for studying host-parasite signaling in the Scrophulariaceae. Parasitic members of this family form subterranean connections, or haustoria, on neighboring host roots to access host water and nutrients. These parasitic organs develop in response to haustorial-inducing factors contained in host root exudates. A well-characterized inducing factor, 2, 6-dimethoxy-p-benzoquinone (DMBQ), can be used to trigger in vitro haustorium formation in the roots of Triphysaria. We have assayed three species, Triphysaria eriantha (Benth.) Chuang and Heckard, Triphysaria pusilla (Benth.) Chuang and Heckard, and Triphysaria versicolor Fischer and C. Meyer, for haustorium development in response to DMBQ. There were significant differences between the species in their ability to recognize and respond to this quinone. Ninety percent of T. versicolor individuals responded, whereas only 40% of T. pusilla and less than 10% of T. eriantha formed haustoria. Within field collections of self-pollinating T. pusilla, differential responsiveness to DMBQ was seen in distinct maternal families. Assaying haustorium development in subsequent generations of self-pollinated T. pusilla showed that DMBQ responsiveness was heritable. Reciprocal crosses between T. eriantha and T. versicolor demonstrated that DMBQ responsiveness was influenced by maternal factors. These results demonstrate heritable, natural variation in the recognition of a haustorial-inducing factor by a parasitic member of the Scrophulariaceae. 相似文献
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The high dependence of herbivorous insects on their host plants implies that plant invaders can affect these insects directly,
by not providing a suitable habitat, or indirectly, by altering host plant availability. In this study, we sampled Asteraceae
flower heads in cerrado remnants with varying levels of exotic grass invasion to evaluate whether invasive grasses have a
direct effect on herbivore richness independent of the current disturbance level and host plant richness. By classifying herbivores
according to the degree of host plant specialization, we also investigated whether invasive grasses reduce the uniqueness
of the herbivorous assemblages. Herbivorous insect richness showed a unimodal relationship with invasive grass cover that
was significantly explained only by way of the variation in host plant richness. The same result was found for polyphagous
and oligophagous insects, but monophages showed a significant negative response to the intensity of the grass invasion that
was independent of host plant richness. Our findings lend support to the hypothesis that the aggregate effect of invasive
plants on herbivores tends to mirror the effects of invasive plants on host plants. In addition, exotic plants affect specialist
insects differently from generalist insects; thus exotic plants affect not only the size but also the structural profile of
herbivorous insect assemblages. 相似文献
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Ai-Rong Li Yun-Ju Li Sally E. Smith F. Andrew Smith Kai-Yun Guan 《Annals of botany》2013,112(6):1099-1106
Background and Aims
Facultative root hemiparasitic plants generally have a wide host range, but in most cases show an obvious host preference. The reasons for the marked difference in growth performance of hemiparasites when attached to different hosts are not fully understood. In this study, the hypothesis was tested that hemiparasites showing a preference for different hosts have different nutrient requirements.Methods
Two facultative root hemiparasitic Pedicularis species (P. rex and P. tricolor) with a different host dependency and preference were used to test their responses to inorganic solutes. The effects of nitrogen, phosphorus and potassium on growth of the hemiparasitic plants not attached to a host were determined, using an orthogonal design in pot cultivation under greenhouse conditions. Variables including biomass, shoot nutrient concentration, root:shoot (R:S) ratios and the number of haustoria were measured.Key Results
As in autotrophic plants, nutrient deficiency reduced dry weight (DW) and nutrient concentrations in the root hemiparasites. Nitrogen and phosphorus significantly influenced growth of both Pedicularis species, while potassium availability influenced only shoot DW of P. rex. Nitrogen had far more effect on growth of P. rex than on P. tricolor, while phosphorus deficiency caused more marked growth depression in P. tricolor than in P. rex. Pedicularis rex grew faster than P. tricolor in a range of nutrient supplies. Different patterns of biomass allocation between the two Pedicularis species were observed. While P. rex invested more into roots (particularly fine rootlets) than P. tricolor, the number of haustoria produced by P. rex was relatively much lower than that produced by P. tricolor, which had a much smaller root system.Conclusions
The two Pedicularis species differ in nutrient requirements and biomass allocation. Distinct interspecific traits in growth and nutrient requirements can be driving forces for the differential interactions between hemiparasites and their hosts. 相似文献11.
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The plasma membrane (PM) of eukaryotic cells is not only an outermost covering to contain and protect inner molecules required for cell viability but also a place where communications dynamically occur with adjacent cells and environments including pathogens. However the selective permeability limits the free translocation of information across the PM between cells. Therefore, eukaryotic cells have invented an elaborate machinery to safely export and import proteins and small molecules within a membrane-wrapped container called a vesicle. Upon infection, a host plant cell also actively interacts with a phytopathogen to achieve its goal, defense to frustrate the pathogen attempt. To understand communications between pathogens and plants, hence this review is mainly focused on molecular transport events that occur at the host PM during plant immune responses. 相似文献
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Catherine E. Bach 《Oecologia》1986,68(4):580-584
Summary The effects of host plant patch size on the abundances of two specialist herbivores (the chrysomelid beetle, Acalymma innubum and the pentatomid bug, Piezosternum subulatum) were investigated in a natural forest community in the Virgin Islands. Abundances were compared early and late in the season in different sized patches of the cucurbit host plant (Cayaponia americana) growing in open habitat (with no surrounding plant community) and forest habitat (with diverse surrounding plant community). For both herbivore species, adult abundances per patch were positively correlated with patch leaf area, but there was a significant patch size effect (i.e., correlation between herbivore density per unit plant and patch leaf area) only for beetles in the forest habitat. Both herbivore species were significantly affected by surrounding plant diversity, but in opposite ways: beetles were more abundant in open patches whereas bugs were more abundant in forest patches. Relationships between abundance and patch size in open and forest patches changed through the season for both herbivore species. These changing abundance patterns are discussed with respect to (1) increases in the diversity of the plant community surrounding host plant patches, and (2) differences in herbivore movement patterns. 相似文献
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Millar AJ 《Journal of experimental botany》2004,55(395):277-283
Eukaryotes and some prokaryotes have adapted to the 24 h day/night cycle by evolving circadian clocks, which now control very many aspects of metabolism, physiology and behaviour. Circadian clocks in plants are entrained by light and temperature signals from the environment. The relative timing of internal and external events depends upon a complex interplay of interacting rhythmic controls and environmental signals, including changes in the period of the clock. Several of the phytochrome and cryptochrome photoreceptors responsible have been identified. This review concentrates on the resulting patterns of entrainment and on the multiple proposed mechanisms of light input to the circadian oscillator components. 相似文献
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John I. Yoder 《Planta》1997,202(4):407-413
Parasitic plants use host molecules to trigger developmental programs essential for parasitism. One such program governs
the initiation, development, and function of haustoria, parasite-specific organs responsible for attachment and invasion of
host tissues. Haustoria development can be initiated by several different molecules produced by appropriate host species.
We are interested in understanding how these signals are interpreted by two related facultative parasites, Triphysaria eriantha (Benth.) Chuang and Heckard, and T. versicolor Fischer and C. Meyer, to distinguish their own roots from those of potential hosts. We used an in vitro bioassay to determine
what proportion of different Triphysaria populations formed haustoria in the presence and absence of closely related and unrelated host species. We found that the
proportion of plants with haustoria was the same whether the plants were grown in isolation or with a conspecific host. In
contrast, a significantly higher proportion of plants made haustoria when the host was a congeneric Triphysaria. Plants with haustoria neither enhanced nor inhibited other plants' propensity to form haustoria. Together these results
indicate that qualitative differences exist in haustorium-inducing factors exuded by closely related species. The highest
proportion of Triphysaria had haustoria when grown with Arabidopsis thaliana (L.) Heynh. Even in this case, however, some Triphysaria failed to develop haustoria. Interestingly, the percentage of haustoria that had vessel elements was higher when connections
were made with Arabidopsis than with another Triphysaria. These results demonstrate that host recognition can be manifested at multiple points in haustorium development.
Received: 18 December 1996 / Accepted: 14 February 1997 相似文献
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Bioassay approaches to observing behavioural responses of adult female Cydia molesta to host plant odour 总被引:1,自引:0,他引:1
D. Natale L. Mattiacci A. Hern E. Pasqualini S. Dorn 《Journal of Applied Entomology》2004,128(3):182-187
Abstract: Three different olfactometers were evaluated in order to develop a bioassay procedure testing for the olfactory responses of Cydia molesta . Females were tested individually using a linear and a Y-tube olfactometer, and in groups using a dual-choice arena. Room temperature, relative humidity, light intensity, airflow, age of the moths and odour source were kept constant during experiments. The odour source tested was a green shoot of peach excised 10 min before experiments started. Cydia molesta females showed a significant response to this plant odour in all olfactometers. A number of qualitative aspects were found to be in favour of the dual choice arena as a tool for screening potentially attractive odour sources. It allowed for a differentiation of the response of mated and virgin females. Experimental conditions allowed the circadian rhythm of insects to be mimicked. Manipulation of individuals is reduced and flight is not precluded. 相似文献