Conservation genetics: beyond the maintenance of marker diversity

One of the major problems faced by conservation biologists is the allocation of scarce resources to an overwhelmingly large number of species in need of preservation efforts. Both demographic and genetic information have been brought to bear on this problem; however, the role of information obtained from genetic markers has largely been limited to the characterization of gene frequencies and patterns of diversity. While the genetic consequences of rarity may be a contributing factor to endangerment, it is widely recognized that demographic factors often may be more important. Because patterns of genetic marker variation are influenced by the same demographic factors of interest to the conservation biologist, it is possible to extract useful demographic information from genetic marker data. Such an approach may be productive for determining plant mating systems, inbreeding depression, effective population size, and metapopulation structure. In many cases, however, data consisting only of marker frequencies are inadequate for these purposes. Development of genealogical based analytical methods coupled with studies of DNA sequence variation within and among populations is likely to yield the most information on demographic processes from genetic marker data. Indeed, in some cases it may be the only means of obtaining information on the long-term demographic properties that may be most useful for determining the future prospects of a species of interest.     

Evolution of resident oral bacterial biota in BALB/c mice during pregnancy and lactation

To assess the influence of pregnancy and lactation on the oral microbial ecology of BALB/c mice, we followed the distribution of the predominant oral bacteria of four groups of these mice during these two periods. Compared with nonpregnant control female mice of the same age maintained under the same conditions, the distribution of the resident oral bacterial species differed significantly only during the lactation period (8–16 days after parturition). This difference could possibly be attributed to hormonal influences and/or grooming habits.     

The major locus for multifactorial nonsyndromic cleft lip maps to mouse Chromosome 11

Cleft lip with or without cleft palate, CL(P), a common human birth defect, has a genetically complex etiology. An animal model with a similarly complex genetic basis is established in the A/WySn mouse strain, in which 20% of newborn have CL(P). Using a newly created congenic strain, AEJ.A, and SSLP markers, we have mapped a major CL(P)-causing gene derived from the A/WySn strain. This locus, here named clf1 (cleft lip) maps to Chromosome (Chr) 11 to a region having linkage homology with human 17q21-24, supporting reports of association of human CL(P) with the retinoic acid receptor alpha (RARA) locus.     

Comparison of Techniques for the Production of Sclerotinia trifoliorum Ascospores in the Laboratory for Forage Legumes Resistance Tests

This study aimed to improve the production, under controlled conditions, of Sclerotinia trifoliorum ascospores to be used for selection tests on forage legumes. Sclerotia of this fungus, produced in the laboratory, were buried 1–2 cm deep in permanently soaked vermiculite, at T = 15°C, 12/24 h of fluorescent light, air moisture >80% in order to differentiate apothecia. The ascospores were harvested by aspiration and collected on a membrane filter. Various types of apparatus containing sclerotia have been tested for their ability to maintain live apothecia and for the facility of spore catching. The aspiration method has been found to be much more efficient than the previous method of cutting off apothecia. Moreover, it was observed that using this harvesting technique the best apparatus presented small and independent compartments (truncated plastic bottles). The ascospores can be stored, on the membrane filter at 5°C and in dry conditions in order to preserve their germinating abilityfor, a period of 3 months at least. This spore harvesting method permits avaibility of large quantities of a cheap inoculum for S. trifoliorum resistance test on forage legumes all year round.     

Oxidative stress responses in transgenic tobacco containing altered levels of glutathione reductase activity

A pea glutathione reductase cDNA was expressed in tobacco. Three classes of construct were used which gave a range of elevated levels of glutathione reductase (GR) activity in the cytosol (GR32), chloroplasts (GR36), or in both chloroplasts and mitochondria (GR46). In some transgenic progeny (T₂) from self-fertilized GR32 and GR36 primary transformants, having approximately twofold elevation of GR activity as compared with recessive siblings, there was an amelioration of the effect on leaf discs of up to 15 µM paraquat. However, lines with similarly elevated levels of GR activity showed no decreased sensitivity to the herbicide. None of the GR32 and GR36 lines was less sensitive to ozone. Conversely, T₂ progeny of GR46 lines, with greater than 4.5-fold elevations of GR activity, showed no reduced sensitivity to paraquat but two out of four of these lines were less sensitive to ozone fumigation. The differential response to stress co-segregated with the presence of the transgene but there was no relationship between the degree of stress response and the level of GR activity. There was an elevation in the total glutathione pool in all lines showing increased GR activity but there was no change in the ratio of oxidized to reduced glutathione. These results demonstrate that the mechanisms of protection against ozone and paraquat are different although both can be mediated by elevated GR activity.     

Oxidative Protective Mechanisms and Resistance to the Dicarboximide Fungicide, Iprodione, in Alternaria alternata

The free radical scavengers α-tocopherol and butylated hydroxytoluene, but not ascorbate, diminished the growth-inhibiting effects of the dicarboximide fungicide, iprodione in Alternaria alternata. Growth of A. alternata in the presence of iprodione increased the activities of superoxide dismutase and glutathione reductase while catalase was unaffected. Four iprodione sensitive and four iprodione resistant isolates of A. alternata were compared for activity of free radical enzymes. The isolates of A. alternata resistant to iprodione had more catalase activity than those which were sensitive, but did not differ in superoxide dismutase of glutathione reductase, activities. 3-Amino-1.24.-triazole, a specific inhibitor of catalas, reduced the ability of DAR 69775, a dicarboximide resistant isolate of A. alternata. to grow in the presence of iprodione. In A. alternata dicarboximide resistance appeats to be at least partially mediated by enhanced activitiesof, catalase.