Detection and Elimination of Viruses in Callus, Somatic Embryos and Regenerated Plantlets of Grapevine

The distribution of some grapevine viruses in flower explants, embryogenic and non-embryogenic calli, single somatic embryos and plants regenerated from embryogenic cultures was investigated by RT-PCR and ELISA. Immature anthers and ovaries of the cultivars Grignolino infected by GRSPaV, GLRaV-1 and GVA, Müller-Thurgau infected by GRSPaV and GLRaV-3 and Bosco infected by GRSPaV were cultivated on media inducing indirect somatic embryogenesis. Viruses were detected both in anthers and ovaries. Four months after culture initiation 65.6% of tested calli were infected by at least one virus; high percentages of virus infection were found in calli originating from ovaries. No virus was detected in calli tested 8 months after culture initiation, as well as in single somatic embryos or in embryo-derived plantlets. Somatic embryogenesis confirmed its effectiveness in eliminating phloem-limited grapevine viruses. Regeneration of RT-PCR negative plantlets occurred even when at least a sector of the callus was still infected: the mechanism whereby somatic embryos are freed of some viruses could be related to the rapid proliferation of embryogenic cells within the callus or to the origin of the embryogenic callus from virus-free cells within the original explant.     

A new kaurane diterpene dimer from Parinari campestris

A new kaurane diterpene dimer, 15-oxozoapatlin-13alpha-yl-10'alpha,16'alpha-dihydroxy-9'alpha-methyl-20'-nor-kauran-19'-oic acid gamma-lactone-17'-oate (1), together with the known 13-hydroxy-15-oxozoapatlin (2), 10alpha,13alpha,16alpha,17-tetrahydroxy-9alpha-methyl-15-oxo-20-nor-kauran-19-oic acid gamma-lactone (3), 2alpha,10alpha,13alpha,16alpha,17-pentahydroxy-9alpha-methyl-15-oxo-20-nor-kauran-19-oic acid (19,10)-lactone (4), 3alpha,10alpha,13alpha,16alpha,17-pentahydroxy-9alpha-methyl-15-oxo-20-nor-kauran-19-oic acid gamma-lactone (5), and 1beta,16alpha,17-trihydroxy-ent-kaurane (6) were isolated from the leaves of Parinari campestris and identified on the basis of detailed spectral analysis, including 2D NMR spectrometry and ESI-MS.     

Central Diabetes Insipidus in a Dog With a Pro-Opiomelanocortin-Producing Pituitary Tumor ot Causing Hyperadrenocorticism

Central diabetes insipidus was diagnosed by vasopressin measurements during hypertonic stimulation in a 9-year-old male giant Schnauzer with polyuria and polydipsia. The impaired release of vasopressin was believed to be caused by a large pituitary tumor, which was visualized by computed tomography. Studies of the function of the anterior lobe and the pars intermedia of the pituitary gland were conducted, and high concentrations of ACTH and α-melanotrophic hormone (α-MSH) were found without concomitant hyperadrenocorticism. Studies of the molecular size of the immunoreactive ACTH in plasma by gel filtration revealed that most of the circulating immunoreactivity was not ACTH but its precursor pro-opiomelanocortin (POMC) and low-molecular-weight POMC-derived peptides. The pituitary tumor of this dog probably originated from melanotrophic cells of the pars intermedia. The sensitivity of the pituitary-adrenocortical system for the suppressive effect of dexamethasone was unaffected.     

Phosphorus fractions and dynamics as affected by land-use changes in the Central Mexican highlands

Land-use change from forest to agriculture in the volcanic ash-derived soils of Mexico has increased over recent decades. It is likely that land uses and management practices, particularly fertilizer use have affected phosphorus (P) distribution and availability. The objective of this study was to evaluate the effects of land-use types (native forest and maize mono-cropping), and the related P addition, on the forms and distribution of soil P and their isotopic exchangeability. An Andisol, sampled from a cropping site, along with the contiguous area under native forest was treated with ³²P-labelled potassium phosphate (KH₂³²PO₄). The soil samples were extracted after incubation times of 7, 21, 35 and 49 days. Phosphorus content and ³²P recovery in fractions sequentially extracted were assessed for each incubation time. Total soil P was dominated by inorganic fractions (79 to 86%) in both land-use types. Resin-Pi, bicarbonate extractable inorganic P (Bic-Pi) and sodium hydroxide extractable inorganic P (NaOH_0.1-Pi) were all raised with P addition. However, the proportion of organic P fraction was reduced under cropped soil. The recovery of ³²P in soils with P addition indicates that resin-Pi, Bic-Pi and NaOH_0.1-Pi comprised nearly all the exchangeable P. In native soils with no P addition, more than 19% of the ³²P was recovered in Bic-Po and NaOH_0.1-Po forms. This finding indicates that organic P cycling is crucial when soil Pi reserves are presented in an inadequate amount. Ecologically based management has to be designed for replenishment and succeeding maintenance of soil organic P compounds to increase sustainable agricultural production.     

Enhancing food-safety education through shared teaching resources

The American public is concerned about food safety, and there is a growing realization that we are ill equipped to handle major food-borne illness outbreaks and bioterrorism. Since veterinary medicine plays an important role in assuring the safety of our nation's food supply, we would like to present to veterinary and public health educators a newly emerging resource for food-safety educational materials. This article describes an integrative collaborative approach for the creation and dissemination of engaging food-safety teaching resources for veterinary faculty. This USDA-funded project, Design to Dissemination: Developing Materials and Repository for Integrative Veterinary Food Safety Education, involves expert teachers in diverse fields and from many veterinary schools. The purpose of the project is to create materials that teach students food safety from farm to fork, and it offers teachers clinically relevant teaching resources that are difficult to create or locate. The educational materials are being created as smaller "building blocks" of content, commonly referred to as "learning objects" (LOs), focused on individual learning objectives. These learning objects are placed in the Veterinary Food Safety Education Learning Object Repository, where they are catalogued, stored, and kept accessible and where faculty can search, evaluate, and download teaching materials to use in their courses. In this way the learning objects can be more easily shared and reused or repurposed for other courses and applications. With this article we hope to excite faculty in veterinary schools and public-health programs and encourage them to use the repository and participate in piloting the educational materials.     

Variations in sucrose and ABA concentrations are concomitant with heteroblastic leaf shape changes in a rhythmically growing species (Quercus robur)

In rhythmically growing woody species such as common oak (Quercus robur L.), stem growth is discontinuous and a bud forms at regular intervals at the shoot apex. These buds are composed of different types of leaves: laminate, aborted lamina and scale. The change in heteroblastic leaf shape from laminate to aborted lamina leaves is regarded as one of the events marking shoot growth arrest. To better understand the determinism of heteroblastic leaf shape change and thus, of rhythmicity, we studied morphogenetic events during the early days of the second flush of growth in oak, as well as changes in sucrose metabolism and abscisic acid (ABA) concentrations in control plants expressing the heteroblastic leaf shape change and in defoliated plants showing no heteroblastic leaf shape change and producing only laminate leaves. In control plants, the leaf shape change was underway on Day 5 of the second flush with the differentiation of the first two aborted lamina leaves. Sucrose concentration in the apices of control plants decreased between Days 3 and 5 during differentiation of the aborted lamina leaves. An inverse pattern was observed in defoliated plants, suggesting that sucrose acts as a signal triggering heteroblastic leaf shape changes. During the same period, acid cell wall invertase activity was high in young stem and laminate leaves of control plants, whereas the activity remained constant and low in the apices. If the laminate leaves were removed, the increase in apical sucrose concentration was proportionally higher than the decrease in apical acid vacuolar invertase activity, suggesting that, in the absence of young leaves, sucrose is imported to the apex. The sucrose concentration in the apex is therefore likely to be affected by trophic competition with the expanding laminate leaves. The decrease in apex sucrose concentration may be one of the mechanisms driving heteroblastic leaf shape change. Differentiation of aborted lamina leaves was followed by a decrease in the organogenic activity of the shoot apical meristem (SAM) between Days 7 and 9. High concentrations of ABA are associated with differentiation of aborted lamina and scale leaves and with low SAM organogenic activity. Shoot apical meristem organogenic activity remained high and ABA concentration in the apex remained low in defoliated plants producing only photosynthetic leaves. These results suggest that (1) ABA is involved in the gradual conversion of embryonic leaves to abnormal leaves, thereby regulating heteroblastic leaf shape changes and (2) changes in ABA concentration influence the intensity of SAM organogenic activity. Heteroblastic development and therefore rhythmic growth could be the result of competition between apices and laminate leaves, with competition first involving sucrose and thereafter ABA.     

U.S. EPA regulation of plant-incorporated protectants: assessment of impacts of gene flow from pest-resistant plants

The U.S. Environmental Protection Agency licenses pesticide-expressing plants under the authority of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA). Transgenes and their pesticidal products represent pesticides under FIFRA and are referred to as plant-incorporated protectants (PIPs). When sexually compatible wild relatives (SCWR) are sympatric with PIP crops, there is a need to assess the potential for adverse effects to man and the environment resulting from transgene introgression in accord with FIFRA requirements. Genetic compatibility, introgression, weediness of SCWR × PIP hybrids, seed dispersal, and dormancy, among other parameters, as well as effects on other species (herbivores and beneficial insects), all need to be considered as part of the risk assessment for experimental use under Section 5 or registration under Section 3 of FIFRA. EPA is currently developing data requirements and guidance toward addressing potential gene flow impacts from PIPs.     

Dynamics of symbiotic establishment between an IAA-overproducing mutant of the ectomycorrhizal fungus Hebeloma cylindrosporum and Pinus pinaster

To clarify the early steps of symbiotic establishment, we studied the dynamics of Pinus pinaster (Ait.) Sol. tap root colonization and mycorrhiza formation by an IAA-overproducing mutant of the ectomycorrhizal fungus Hebeloma cylindrosporum Romagnesi and by the corresponding wild type strain. Differences between wild type and mutant strains were quantitative rather than qualitative and were detected two days after inoculation. Both fungal strains established a typical Hartig net when they colonized the tap roots. Consequently, colonized tap roots exhibited features of a true mycorrhiza and fungal colonization enhanced plant growth. Fungal colonization and Hartig net formation were more rapid with the mutant than with the wild type. Colonization, especially with the mutant strain, increased rhizogenesis and the production of mycorrhizas. The mutant formed a hypertrophic Hartig net in tap roots and mycorrhizal short roots and we obtained evidence that the process of short root transformation into mycorrhiza started before their emergence from the tap root. Hyphae of the Hartig net in the tap root penetrated the cortex of young lateral roots at the beginning of their elongation, after the endodermis layer broke under the pressure of the elongating lateral root. Colonization was inhibited when triiodobenzoic acid was added to the culture medium, providing circumstantial evidence that auxin is involved in mycorrhiza formation.