Zea mays
not annotated - annotated - LINNAEUS only
20840610
The role of abscisic acid and water stress in root herbivore-induced leaf resistance.
* Herbivore-induced systemic resistance occurs in many plants and is commonly assumed to be adaptive. The mechanisms triggered by leaf-herbivores that lead to systemic resistance are largely understood, but it remains unknown how and why root herbivory also increases resistance in leaves. * To resolve this, we investigated the mechanism by which the root herbivore Diabrotica virgifera induces resistance against lepidopteran herbivores in the leaves of Zea mays. * Diabrotica virgifera infested plants suffered less aboveground herbivory in the field and showed reduced growth of Spodoptera littoralis caterpillars in the laboratory. Root herbivory did not lead to a jasmonate-dependent response in the leaves, but specifically triggered water loss and abscisic acid (ABA) accumulation. The induction of ABA by itself was partly responsible for the induction of leaf defenses, but not for the resistance against S. littoralis. Root-herbivore induced hydraulic changes in the leaves, however, were crucial for the increase in insect resistance. * We conclude that the induced leaf resistance after root feeding is the result of hydraulic changes, which reduce the quality of the leaves for chewing herbivores. This finding calls into question whether root-herbivore induced leaf-resistance is an evolved response.
20880205
Factors required for the high CO2 specificity of the anaerobically induced maize GapC4 promoter in transgenic tobacco.
Flooding, a natural cause of anaerobiosis, is often accompanied by high CO(2) concentrations in the flood water. Plants need to respond to these environmental conditions. Strong anaerobic reporter gene activity in tobacco (Nicotiana tabacum) controlled by the glycolytic glyceraldehyde-3-phosphate dehydrogenase (GapC4) promoter from maize (Zea mays) depends on the presence of CO(2) and light. To identify factors required for CO(2) regulated gene expression, promoter deletions fused to the Beta-glucuronidase reporter gene were studied in transgenic tobacco. Deletion of a 40 bp fragment directly upstream of the TATA box leads to increased anaerobic reporter gene activity both, in the presence and absence of CO(2). This deletion does not affect light specific anaerobic expression. A positive correlation between increasing CO(2) concentrations and gene activity is observed. Electrophoretic mobility shift experiments indicate that tobacco nuclear extracts harbour proteins that bind to part of the 40 bp fragment. Database assisted as well as experimental analysis reveal a role for AP2/EREBP transcription factors for conferring the high CO(2) specificity to the GapC4 promoter in tobacco leaves. This work highlights the importance for plants to respond to high environmental CO(2) concentrations under anaerobic conditions.
20946131
Host plant secondary metabolite profiling shows a complex, strain-dependent response of maize to plant growth-promoting rhizobacteria of the genus Azospirillum.
Most Azospirillum plant growth-promoting rhizobacteria (PGPR) benefit plant growth through source effects related to free nitrogen fixation and/or phytohormone production, but little is known about their potential effects on plant physiology. These effects were assessed by comparing the early impacts of three Azospirillum inoculant strains on secondary metabolite profiles of two different maize (Zea mays) cultivars. After 10d of growth in nonsterile soil, maize methanolic extracts were analyzed by reverse-phase high-performance liquid chromatography (RP-HPLC) and secondary metabolites identified by liquid chromatography/mass spectrometry (LC/MS) and nuclear magnetic resonance (NMR). Seed inoculation resulted in increased shoot biomass (and also root biomass with one strain) of hybrid PR37Y15 but had no stimulatory effect on hybrid DK315. In parallel, Azospirillum inoculation led to major qualitative and quantitative modifications of the contents of secondary metabolites, especially benzoxazinoids, in the maize plants. These modifications depended on the PGPR strainxplant cultivar combination. Thus, Azospirillum inoculation resulted in early, strain-dependent modifications in the biosynthetic pathways of benzoxazine derivatives in maize in compatible interactions. This is the first study documenting a PGPR effect on plant secondary metabolite profiles, and suggests the establishment of complex interactions between Azospirillum PGPR and maize.
21039559
Systemic virus-induced gene silencing allows functional characterization of maize genes during biotrophic interaction with Ustilago maydis.
Infection of maize (Zea mays) plants with the corn smut fungus Ustilago maydis leads to the formation of large tumors on the stem, leaves and inflorescences. In this biotrophic interaction, plant defense responses are actively suppressed by the pathogen, and previous transcriptome analyses of infected maize plants showed massive and stage-specific changes in host gene expression during disease progression. To identify maize genes that are functionally involved in the interaction with U. maydis, we adapted a virus-induced gene silencing (VIGS) system based on the brome mosaic virus (BMV) for maize. Conditions were established that allowed successful U. maydis infection of BMV-preinfected maize plants. This set-up enabled quantification of VIGS and its impact on U. maydis infection using a quantitative real-time PCR (qRT-PCR)-based readout. In proof-of-principle experiments, an U. maydis-induced terpene synthase was shown to negatively regulate disease development while a protein involved in cell death inhibition was required for full virulence of U. maydis. The results suggest that this system is a versatile tool for the rapid identification of maize genes that determine compatibility with U. maydis.
21526935
Assessment of attractiveness of cassava as a roosting plant for the melon fly, Bactrocera cucurbitae, and the Oriental fruit fly, B. dorsalis.
Application of bait spray to crop borders is a standard approach for suppression of melon fly, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae) populations and may also be of value for suppression of oriental fruit fly, B. dorsalis (Hendel) populations. Establishment of preferred roosting hosts as crop borders may help to improve suppression of both fruit fly species by providing sites for bait spray applications. In an area-wide B. cucurbitae suppression trial, the question was raised as to whether cassava, Manihot esculenta Crantz (Euphorbiales: Euphorbiaceae), could be used as a B. cucurbitae roosting host. M. esculenta was of interest as a roosting host because, in contrast to many other identified preferred roosting hosts, it would also be a crop potentially increasing the productivity of the crop production system overall. As a short-lived and shrubby perennial, M. esculenta potentially constitutes a crop with more persistent roosting foliage than an annual crop such as corn, Zea mays L. (Cyperales: Poaceae), that has often been planted as a roosting host for B. cucurbitae control. Using protein-baited traps set amidst potted plants placed adjacent to a papaya Carica papaya L. (Violales: Caricaceae) orchard known to have established populations of B. cucurbitae and B. dorsalis, the effectiveness of M. esculenta as a roosting host was assessed by comparing its attractiveness to that of castor bean, Ricinus communis L (Malpighiales: Euphorbiaceae), previously identified as one of the most attractive roosting hosts for B. cucurbitae, and to corn, a crop which has been planted as a roosting host for help in B. cucurbitae control. The results showed that use of M. esculenta as a roosting host is comparable to use of R. communis by both B. cucurbitae and B. dorsalis. These results provide encouragement to incorporate M. esculenta on a farm as a trap crop (i.e. site for bait spray application). This has the advantage of having the trap crop be a crop on its own (as opposed to castor bean) and, among prospective crops that could be used as a trap crop, has foliage more persistent than an annual trap crop such as corn.
21054434
Acclimation to high CO2 in maize is related to water status and dependent on leaf rank.
The responses of C(3) plants to rising atmospheric CO(2) levels are considered to be largely dependent on effects exerted through altered photosynthesis. In contrast, the nature of the responses of C(4) plants to high CO(2) remains controversial because of the absence of CO(2) -dependent effects on photosynthesis. In this study, the effects of atmospheric CO(2) availability on the transcriptome, proteome and metabolome profiles of two ranks of source leaves in maize (Zea mays L.) were studied in plants grown under ambient CO(2) conditions (350 +/- 20 muL L(-1) CO(2) ) or with CO(2) enrichment (700 +/- 20 muL L(-1) CO(2) ). Growth at high CO(2) had no effect on photosynthesis, photorespiration, leaf C/N ratios or anthocyanin contents. However, leaf transpiration rates, carbohydrate metabolism and protein carbonyl accumulation were altered at high CO(2) in a leaf-rank specific manner. Although no significant CO(2) -dependent changes in the leaf transcriptome were observed, qPCR analysis revealed that the abundance of transcripts encoding a Bowman-Birk protease inhibitor and a serpin were changed by the growth CO(2) level in a leaf rank specific manner. Moreover, CO(2) -dependent changes in the leaf proteome were most evident in the oldest source leaves. Small changes in water status may be responsible for the observed responses to high CO(2,) particularly in the older leaf ranks.
21526933
Parasitism of lepidopterous stem borers in cultivated and natural habitats.
Plant infestation, stem borer density, parasitism, and parasitoid abundance were assessed during two years in two host plants, Zea mays (L.) (Cyperales: Poaceae) and Sorghum bicolor (L.) (Cyperales: Poaceae), in cultivated habitats. The four major host plants (Cyperus spp., Panicum spp., Pennisetum spp., and Sorghum spp.) found in natural habitats were also assessed, and both the cultivated and natural habitat species occurred in four agroecological zones in Kenya. Across habitats, plant infestation (23.2%), stem borer density (2.2 per plant), and larval parasitism (15.0%) were highest in maize in cultivated habitats. Pupal parasitism was not higher than 4.7% in both habitats, and did not vary with locality during each season or with host plant between each season. Cotesia sesamiae (Cameron) and C. flavipes Cameron (Hymenoptera: Braconidae) were the key parasitoids in cultivated habitats (both species accounted for 76.4% of parasitized stem borers in cereal crops), but not in natural habitats (the two Cotesia species accounted for 14.5% of parasitized stem borers in wild host plants). No single parasitoid species exerted high parasitism rates on stem borer populations in wild host plants. Low stem borer densities across seasons in natural habitats indicate that cereal stem borer pests do not necessarily survive the non-cropping season feeding actively in wild host plants. Although natural habitats provided refuges for some parasitoid species, stem borer parasitism was generally low in wild host plants. Overall, because parasitoids contribute little in reducing cereal stem borer pest populations in cultivated habitats, there is need to further enhance their effectiveness in the field to regulate these pests.