Relative performance of monohaploid potato clones and their diploid parents at plant level and after protoplast isolation and subsequent fusion

Summary Plant growth performance was studied in 118 potato monohaploids and in their diploid parents. Of these monohaploids 76 were also investigated at the protoplast level and eight of these were used in protoplast fusion experiments as well. No correlation was found between relative performance of greenhouse grown and in vitro grown plants. No or only weak correlations were found between different in vitro characteristics such as plant growth, protoplast yield per gram plant material, plating efficiency and callus growth. This indicates the unpredictability of these characters.The protoplast fusion experiments indicated that only in some genotype combinations increased callus growth rates may be found. However, it is not clear whether such calli were hybrids or not. In protoplast monocultures only diploid and tetraploid regenerants were obtained. After fusion, tetraploids but also some triploids could be regenerated. The finding of triploids indicates that monoploid protoplasts were involved in fusion. Isozyme analysis and morphological assessment of the plants pointed out that the majority of the fusion regenerants were hybrids. The implications of these results are discussed.     

Maternal-effect mutations altering the anterior-posterior pattern of the Drosophila embryo

Summary Mutations in seven different maternal-effect loci on the second chromosome of Drosophila melanogaster all cause alterations in the anterior-posterior pattern of the embryo. Mutations in torso (tor) and trunk (trk) delete the anterior- and posterior-most structures of the embryo. At the same time they shift cellular fates which are normally found in the subterminal regions of the embryo towards the poles. Mutations in vasa (vas), valois (vls), staufen (stau) and tudor (tud) cause two embryonic defects. For one they result in absence of polar plasm, polar granules and pole cells in all eggs produced by mutant females. Secondly, embryos developing inside such eggs show deletions of abdominal segments. In addition, embryos derived from staufen mothers lack anterior head structures, embryos derived from valois mothers frequently fail to cellularize properly. Mutations in exuperantia (exu) cause deletions of anterior head structures, similar to torso, trunk and staufen. However in exu, these head structures are replaced by an inverted posterior end which comprises posterior midgut, proctodeal region, and often malpighian tubules.The effects of all mutations can be traced back to the beginning stages of gastrulation, indicating that the alterations in cellular fates have probably taken place by that time. Analysis of embryos derived from double mutant mothers suggests that these three phenotypic groups of mutants interfere with three different, independent pathways. All three pathways seem to act additively on the system which specifies anterior-posterior cellular fates within the egg.     

Construction of a sequencedClostridium perfringens-Escherichia coli shuttle plasmid

A newClostridium perfringens-Escherichia coli shuttle plasmid has been constructed and its complete DNA sequence compiled. The vector, pJIR418, contains the replication regions from theC. perfringens replicon pIP404 and theE. coli vector pUC18. The multiple cloning site and lacZ gene from pUC18 are also present, which means that X-gal screening can be used to select recombinants inE. coli. Both chloramphenicol and erythromycin resistance can be selected inC. perfringens andE. coli since pJIR418 carries theC. perfringens catP and ermBP genes. Insertional inactivation of either the catP or ermBP genes can also be used to directly screen recombinants in both organisms. The versatility of pJIR418 and its applicability for the cloning of toxin genes fromC. perfringens have been demonstrated by the manipulation of a cloned gene encoding the production of phospholipase C.     

Repeat Photography as a Method in Visual Anthropology

This paper explores the use of repeat photography as a powerful method to produce knowledge about place. I use examples from research in Waterton Lakes National Park, Canada, to describe the process of making a repeat photograph, from locating images in archives, to the embodied act of locating a historic vantage point, to the production of a new photograph. This act brings art and anthropology into a shared space to recreate photographs, an act that goes beyond looking at historical images in archives to move our thinking onward about how we relate to images.     

Divisestylus gen. nov. (aff. Iteaceae), a fossil saxifrage from the Late Cretaceous of New Jersey, USA

Fossilized flowers and fruits from the Upper Cretaceous (Turonian, ca. 90 million years [my] before present) Raritan Formation of New Jersey are described as the new genus Divisestylus with two species, D. brevistamineus and D. longistamineus. The fossils are fusainized and three-dimensionally preserved. Morphological characteristics suggest affinities with extant Saxifragaceae and Iteaceae, two closely related families in Saxifragales. Similarities include a pentamerous perianth, calyx fused below into a hypanthium with free sepal lobes above, haplostemonous androecium with stamens situated opposite the calyx lobes, inferior ovary, bicarpellate gynoecium, numerous ovules on axile placentas, conspicuous intrastaminal nectary ring, and capsulate fruit opening apically. The unique fusion of the gynoecium, with carpels and stigmas fused but styles free, indicates closer affinities with extant Iteaceae, whereas other characters, such as basifixed anthers in D. brevistamineus, tricolpate and striate pollen grains, and anomocytic stomata, indicate closer affinities to Saxifragaceae. Cladistic analyses utilizing molecular data from a previously published analysis and morphological data as well as morphological data alone demonstrate the fossils share a more recent common ancestor with Iteaceae than Saxifragaceae, thereby making Divisestylus the oldest fossils known with clear affinities to Iteaceae.     

Functional analysis of a DNA-shuffled movement protein reveals that microtubules are dispensable for the cell-to-cell movement of tobacco mosaic virus

Microtubules interact strongly with the viral movement protein (MP) of Tobacco mosaic virus (TMV) and are thought to transport the viral genome between plant cells. We describe a functionally enhanced DNA-shuffled movement protein (MP(R3)) that remained bound to the vertices of the cortical endoplasmic reticulum, showing limited affinity for microtubules. A single amino acid change was shown to confer the MP(R3) phenotype. Disruption of the microtubule cytoskeleton in situ with pharmacological agents, or by silencing of the alpha-tubulin gene, had no significant effect on the spread of TMV vectors expressing wild-type MP (MP(WT)) and did not prevent the accumulation of MP(WT) in plasmodesmata. Thus, cell-to-cell trafficking of TMV can occur independently of microtubules. The MP(R3) phenotype was reproduced when infection sites expressing MP(WT) were treated with a specific proteasome inhibitor, indicating that the degradation of MP(R3) is impaired. We suggest that the improved viral transport functions of MP(R3) arise from evasion of a host degradation pathway.     

Symplastic connection is required for bud outgrowth following dormancy in potato (Solanum tuberosum L.) tubers

To gain greater insight into the mechanism of dormancy release in the potato tuber, an investigation into physiological and biochemical changes in tuber and bud tissues during the transition from bud dormancy (immediately after harvest) to active bud growth was undertaken. Within the tuber, a rapid shift from storage metabolism (starch synthesis) to reserve mobilization within days of detachment from the mother plant suggested transition from sink to source. Over the same period, a shift in the pattern of [U-(14)C]sucrose uptake by tuber discs from diffuse to punctate accumulation was consistent with a transition from phloem unloading to phloem loading within the tuber parenchyma. There were no gross differences in metabolic capacity between resting and actively growing tuber buds as determined by [U-(14)C]glucose labelling. However, marked differences in metabolite pools were observed with large increases in starch and sucrose, and the accumulation of several organic acids in growing buds. Carboxyfluorescein labelling of tubers clearly demonstrated strong symplastic connection in actively growing buds and symplastic isolation in resting buds. It is proposed that potato tubers rapidly undergo metabolic transitions consistent with bud outgrowth; however, growth is initially prevented by substrate limitation mediated via symplastic isolation.     

Fungal endophytes in a 400-million-yr-old land plant: infection pathways, spatial distribution, and host responses

The Early Devonian Rhynie chert has been critical in documenting early land plant-fungal interactions. However, complex associations involving several fungi that enter into qualitatively different relationships with a single host plant and even interact with one another have not yet been detailed. Here, we studied petrographic thin sections of the Rhynie chert plant Nothia aphylla. Three fungal endophytes (co)occur in prostrate axes of this plant: narrow hyphae producing clusters of small spores; large spherical spores/zoosporangia; and wide aseptate hyphae that form intercellular vesicles in the cortex. Host responses on attack include bulging of infected rhizoids, formation of encasement layers around intracellular hyphae, and separation of infected from uninfected tissues by secondarily thickened cell walls. A complex simultaneous interaction of N. aphylla with three endophytic fungi was discovered. The host responses indicate that some of the mechanisms causing host responses in extant plants were in place 400 million yr ago. Anatomical and life history features of N. aphylla suggest that this plant may have been particularly susceptible to colonization by fungi.     

Localization and domain characterization of Arabidopsis golgin candidates

Golgins are large coiled-coil proteins that play a role in tethering of vesicles to Golgi membranes and in maintaining the overall structure of the Golgi apparatus. Six Arabidopsis proteins with the structural characteristics of golgins were isolated and shown to locate to Golgi stacks when fused to GFP. Two of these golgin candidates (GC1 and GC2) possess C-terminal transmembrane (TM) domains with similarity to the TM domain of human golgin-84. The C-termini of two others (GC3/GDAP1 and GC4) contain conserved GRAB and GA1 domains that are also found in yeast Rud3p and human GMAP210. GC5 shares similarity with yeast Sgm1p and human TMF and GC6 with yeast Uso1p and human p115. When fused to GFP, the C-terminal domains of AtCASP and GC1 to GC6 localized to the Golgi, showing that they contain Golgi localization motifs. The N-termini, on the other hand, label the cytosol or nucleus. Immuno-gold labelling and co-expression with the cis Golgi Q-SNARE Memb11 resulted in a more detailed picture of the sub-Golgi location of some of these putative golgins. Using two independent assays it is further demonstrated that the interaction between GC5, the TMF homologue, and the Rab6 homologues is conserved in plants.