Characterization of disomic addition lines Brassica napus-Brassica nigra by isozyme,fatty acid,and RFLP markers

Summary Six Brassica napus — B. nigra disomic addition lines were characterized by isozyme, fatty acid, and RFLP markers. The markers were arranged in six synteny groups, representing six of the eight chromosomes present in the B. nigra genome. Synteny group 1 displayed high levels of linoleic and linolenic acids in the seeds of the B. nigra parent. Synteny group 3 accumulated higher levels of eicosenoic and erucic acid than B. nigra. Three of the lines transmitted the alien chromosome to 100% of the progeny. The rest had variable transmission rates but all were above 50%. Most of the lines produced disomic addition plants in their progeny, suggesting pollen transmission of the alien chromosome. In addition to the marked lines, six others remained unmarked. These could be grouped into two classes according to their alien chromosome transmission. It is likely that they represent the two other B. nigra chromosomes that remained uncharacterized by the markers. No diploid individuals carrying B. nigra genome-specific markers were detected in the progenies studied.     

Replication process of the parvovirus H-1. VIII. Partial denaturation mapping and localization of the replication origin of H-1 replicative-form DNA with electron microscopy.

Partial denaturation mapping, restriction endonuclease digestion, and electron microscopy were used to determine which end of the linear duplex replicative-form (RF) DNA molecule contains the origin of RF replication for the parvovirus H-1. This origin was localized within approximately 300 base pairs of the arbitrarily designated right end of the RF DNA, in the EcoRI or HaeII-A fragment. Based on denaturation behavior in formamide, the right end was also found to have a relatively high guanine plus cytosine content, whereas the region adjacent to the left terminus of the RF DNA molecule was adenine plus thymine rich.     

Characterization of a phosphoglycerate kinase deficiency variants not associated with hemolytic anemia.

The properties of a variant phosphoglycerate kinase (PGK) found in a large German clan were examined. The normal and variant enzymes, isolated by affinity chromatography, have the same molecular weight, specific activity, substrate affinity, and nearly identical pH-optima. Using immunoinactivation and immunodiffusion, the same specific activity for both forms was again determined. Since the enzymatic activity in older and younger erythrocytes varied only slightly, and since the specific activity of the variant was normal, the variant seems to be stable in vivo. This suggests that the decreased enzyme content is due to a decreased synthesis rate. The variant PGK described here is distinctly different from the known PGK variants and has been designated as "PGK München."     

Selection of stable Brassica napus-Brassica juncea recombinant lines resistant to blackleg (Leptosphaeria maculans). 2. A ‘to and fro’ strategy to localise and characterise interspecific introgressions on the B. napus genome

 A new strategy to localise and characterise interspecific introgressions in the genus Brassica is presented. It consists of the localisation of RAPD specific markers from the donor species (B. juncea) by RFLP on a genetic map of the recipient (B. napus) and on the observation of the disappearance of rapeseed markers in recombinant lines. With this method, we localised an interspecific introgression of B. juncea, which confers blackleg resistance at the cotyledon stage in B. napus, on the linkage group DY17 of the previously determined B. napus genetic map. The estimated size of the substituted B. napus fragment was 39 cM, and the resistance gene was introgressed into the rapeseed genome by homologous recombination. The significance of the different strategies used and the implication of these results in breeding programs are discussed. Received: 23 August 1997 / Accepted: 13 October 1997     

Injection tube differentiation in gun cells of a haptoglossa species which infects nematodes

The gun cells which develop from germinating cysts in Haptoglossa produce a specialized infection apparatus, the injection tube. Upon eversion this tube fires a missile-like projectile which penetrates the host cuticle and then forms an infective sporidium within the body cavity of the nematode host. The temporal assembly of this complex cell organelle has been determined by serial-section reconstructions of maturing gun cells in a previously undescribed Haptoglossa species. The differentiation of the partially walled inverted injection tube is an unusual example of internal tube growth, in which membrane and wall assembly are temporally separated. There is no evidence that the shape of this inverted tube, which coils around the nucleus until it doubles back on itself, is dictated by the disposition of cytoplasmic microtubules. However, actin-like material was associated with the delimiting membrane of the differentiating tube, particularly in the regions of extension. From these studies it seems likely that the "head and buttress" structures previously depicted as the barbed tip of the "harpoon-like" penetration missile are part of a separate, structurally complex system which we suggest locks the "missile" into position in the invaginated injection tube. From this detailed account of cell architecture, models for the likely mechanism of infection cell firing are discussed, and unresolved questions relating to the cell biology and biochemistry of these complex organelles are highlighted. Copyright 1998 Academic Press.     

Amphiphile-induced vesiculation in aged hereditary spherocytosis erythrocytes indicates normal membrane stability properties under non-starving conditions.

Aged HS erythrocytes with a defined primary defect in band 3 protein or ankyrin were incubated with amphiphiles (detergents) at sublytic concentrations (37 C, 60 min) or glucose-starved (37 C, 24 h). In line with previous studies, the release of AChE (exovesicles) from HS erythrocytes during glucose-starvation was significantly higher (11%) compared to that from control erythrocytes (1%). Control and HS cells responded, however, similarly to amphiphile-treatment (non-starving conditions). Amphiphiles induced similar types of shape alterations and a similar amount of AChE release (14-15%). Furthermore, the size and shape of amphiphile-induced exo- and endovesicles released from control and HS erythrocytes were similar. The results suggest that the stability properties of the membrane are not seriously disturbed in aged HS erythrocytes under non-starving conditions.     

Chromosome 'speed dating' during meiosis of polyploid Brassica hybrids and haploids

Given their tremendous importance for correct chromosome segregation, the number and distribution of crossovers are tightly controlled during meiosis. In this review, we give an overview of crossover formation in polyploid Brassica hybrids and haploids that illustrates or underscores several aspects of crossover control. We first demonstrate that multiple targets for crossover formation (i.e. different but related chromosomes or duplicated regions) are sorted out during meiosis based on their level of relatedness. In euploid Brassica napus (AACC; 2n = 38), crossovers essentially occur between homologous chromosomes and only a few of them form between homeologues. The situation is different in B. napus haploids in which crossovers preferentially occur between homeologous chromosomes and a few can then form between more divergent duplicated regions. We then provide evidence that the frequency of crossovers between a given pair of chromosomes is influenced by the karyotypic and genetic composition of the plants that undergo meiosis. For instance, genetic evidence indicates that the number of crossovers between exactly the same pairs of homologous A chromosomes gets a boost in Brassica digenomic tetraploid (AACC) and triploid (AAC) hybrids. Increased autosyndesis within B. napus haploids as compared to monoploid B. rapa and B. oleracea is another illustration of this process. All these observations may suggest that polyploidization overall boosts up crossover machinery and/or that the number of crossovers is modulated through inter-bivalents or univalent-bivalent cross-talk effects. The last part of this review gives an up-to-date account of what we know about the genetic control of homologous and homeologous crossover formation among Brassica species.     

Regional patch dynamics of Cirsium arvense and possible implications for plant‐animal interactions

Abstract. Plant population biology considers the dynamics of plant modules within stands. However, stands themselves may have considerable regional turnover in space and time. These changes in the number, distribution and size of plant stands generate a dynamic spatial pattern with important implications for the spatial and temporal dynamics of phytophagous insects using these plants as a host. During five successive years we studied the regional distribution and patch dynamics of the creeping thistle Cirsium arvense and the distribution of associated populations of the herbivore Urophora cardui (Diptera: Tephritidae), a specialist stem gall former. The study conducted was in a 15 km² heterogeneous, agricultural area in northeastern Bavaria. The distribution of the number of plants per patch was skewed with many more small C. arvense patches than large ones. During the five years of study, there was a 50% increase in the number of C. arvense patches, and a decrease in the mean number of plants per patch (= patch size) to less than half the patch size of the first year. Whilst patch size was randomly distributed in space, patch density showed a consistent, non‐random spatial pattern. Patch density was spatially auto‐correlated, with areas of high or low patch density having a characteristic dimension of ca. 1 km. Patch size was predictable in time and appeared to be regulated by size dependent processes, with the extinction probability of a patch being negatively correlated with its size. Correlated with the decline of C. arvense patch size during the study, the occupancy and total numbers of the herbivore U. cardui had a marked decrease, suggesting that the regional distribution of the stem gall former is not only influenced by patch number but more importantly by the mean patch size. With decreasing patch sizes, U. cardui was faced with an increasingly dynamic landscape due to higher extinction rates of small patches, although the mean distance between host plant patches decreased.     

Metapopulation persistence in dynamic landscapes: the role of dispersal distance

Species associated with transient habitats need efficient dispersal strategies to ensure their regional survival. Using a spatially explicit metapopulation model, we studied the effect of the dispersal range on the persistence of a metapopulation as a function of the local population and landscape dynamics (including habitat patch destruction and subsequent regeneration). Our results show that the impact of the dispersal range depends on both the local population and patch growth. This is due to interactions between dispersal and the dynamics of patches and populations via the number of potential dispersers. In general, long-range dispersal had a positive effect on persistence in a dynamic landscape compared to short-range dispersal. Long-range dispersal increases the number of couplings between the patches and thus the colonisation of regenerated patches. However, long-range dispersal lost its advantage for long-term persistence when the number of potential dispersers was low due to small population growth rates and/or small patch growth rates. Its advantage also disappeared with complex local population dynamics and in a landscape with clumped patch distribution.