Host plant growth response to inoculation withFrankia

Optimum growth conditions and inoculation regimes were determined for severalFrankia strains isolated from both Alnus and Casuarina host plants. Growth conditions were estabilished that allowed a reduction in generation time to less than 15 hours for certain Alnus derivedFrankia. Differences in plant growth response were observed with differing inoculum levels and soil mixtures. Elite strains of Alnus derivedFrankia were isolated that elicited similar growth reponses in allAlnus species tested; however, differences were observed betweenFrankia strains and plant growth response of variousCasuarina species tested.     

Measurement of the body composition of living gray seals by hydrogen isotope dilution

The body composition of living gray seals (Halichoerus grypus) can be accurately predicted from a two-step model that involves measurement of total body water (TBW) by 2H or 3H dilution and application of predictive relationships between body components and TBW that were derived empirically by slaughter chemical analysis. TBW was overestimated by both 2HHO and 3HHO dilution; mean overestimates were 2.8 +/- 0.9% (SE) with 2H and 4.0 +/- 0.6% with 3H. The relationships for prediction of total body fat (TBF), protein (TBP), gross energy (TBGE), and ash (TBA) were as follows: %TBF = 105.1 - 1.47 (%TBW); %TBP = 0.42 (%TBW) - 4.75; TBGE (MJ) = 40.8 (mass in kg) - 48.5 (TBW in kg) - 0.4; and TBA (kg) = 0.1 - 0.008 (mass in kg) + 0.05 (TBW in kg). These relationships are applicable to gray seals of both sexes over a wide range of age and body conditions, and they predict the body composition of gray seals more accurately than the predictive equations derived from ringed seals (Pusa hispida) (Stirling et al., Can. J. Zool. 53: 1021-1027, 1975) and from the equation of Pace and Rathbun (J. Biol. Chem. 158: 685-691, 1945), which has been reported to be generally applicable to mammals.     

Cytological and molecular characterization of a chromosome interchange and addition lines in Cadet involving chromosome 5B of wheat and 6Ag of Lophopyrum ponticum

Efforts to transfer wheat curl mite (Eriophyes tulipae Keifer) resistance from Lophopyrum ponticum 10X (Podb.) Love to bread wheat (Triticum aestivum L.) have resulted in the production of a number of cytogenetic stocks, including an addition line of 6Ag, a ditelo addition line, and a wheat-Lophopyrum translocation line. Characterization of these lines with C-banding, in situ hybridization with a Lophopyrum species-specific repetitive DNA probe (pLeUCD2), and Southern blotting with pLeUCD2 and a 5S ribosomal DNA probe (pScT7) confirmed that the distal portion of the short arm of 6Ag was translocated onto the distal portion of 5BS (5BL. 5BS-6AgS). It was also determined that the ditelo addition was an acrocentric chromosome of 6AgS.     

Low root zone temperature favours shoot B partitioning into young leaves of oilseed rape (Brassica napus)

In previous studies with tropical plant species, low root zone temperature (RZT) induced boron (B) deficiency, but it is not known if the same response to RZT will be expressed in temperate species, like oilseed rape, that are more tolerant of low temperature. The present experiments investigated the effect of RZT (10 and 20°C) on oilseed rape ( Brassica napus L. cv. Hyola 42) response to B in solution culture, in summer and winter. Regardless of canopy growth conditions, low RZT (10°C) promoted the partitioning of shoot B to the actively growing leaves, especially when B supply was low. However, low RZT did not significantly alter net B uptake rates or plant biomass. Low RZT decreased the shoot-to-root ratio, countering the effects of low B which increased it, leading to a decreased demand for B in the shoot at low RZT. At low B supply, B-deficiency symptoms appeared later at 10 than at 20°C, corresponding with higher B concentrations in the youngest fully opened leaves (YOLs) at 10°C RZT. Thus 10°C RZT increased the tolerance to low B supply. As a result, it is concluded that the effect of decreasing RZT on the responses of the temperate species, oilseed rape, to low B supply depends on whether the low RZT is above or below the optimal root temperature for growth.     

Proteolytic inactivation of alpha-1-anti-chymotrypsin. Sites of cleavage and generation of chemotactic activity.

The effect of several microbial and mammalian proteinases on the inhibitory activity of human plasma alpha-1-anti-chymotrypsin (alpha-1-Achy) has been tested. Most of these enzymes caused rapid inactivation of the inhibitor by cleavage at single sites within the reactive-site loop between P5 Lys and P3' Leu, with additional cleavages also being detected in some cases near the NH2 terminus of the native protein. In contrast, two of the enzymes tested failed to inactivate alpha-1-Achy, although they could cause removal of peptides near the NH2 terminus. Studies of neutrophil chemotaxis revealed that native or NH2-terminally truncated alpha-1-Achy was not stimulatory. However, testing of two enzymatically inactivated forms of the inhibitor (alpha-1-Achy), cleaved at widely different positions within the reactive-site loop, indicated that they had become potent chemoattractants at concentrations within the nanomolar range. Competition studies using proteolytically inactivated alpha-1-proteinase inhibitor suggested that the chemotactic activity of the two inactivated serpins was probably mediated by the same mechanism. The physiological relevance of this chemotactic activity is underscored by the results of plasma elimination studies which indicate that alpha-1-Achy is eliminated at approximately the same rate as native alpha-1-Achy, thus prolonging chemotactic stimuli within the tissues.     

Joint Segregation of Biochemical Loci in Salmonidae. II. Linkage Associations from a Hybridized Salvelinus Genome (S. NAMAYCUSHxS. FONTINALIS)

The results of more than 300 pairwise examinations of biochemical loci for joint segregation in brook trout (Salvelinus fontinalis) and in the hybridized genome of lake trout (S. namaycush) x brook trout are summarized. Nineteen loci have been assigned to the following eight linkage groupings on the basis of nonrandom assortment, including cases of both classical linkage and pseudolinkage: ODH with PMI with PGI-3, PGI-2 with SDH, ADA-1 with AGP-2, AAT-(1,2) with AGP-1 with MDH-1, MDH-3 with MDH-4, LDH-3 with LDH-4, IDH-3 with ME-2 and GUS with CPK-1. Pseudolinkage (an excess of nonparental progeny types) was observed only for male testcross parents. The results suggest that this phenomenon involves homeologous chromosome arms as evidenced by the de novo association of presumed duplicate loci in each case. Classical linkage has not been found for the five pairs of duplicate loci examined in Salvelinus, suggesting that not all of the eight metacentrics in the haploid complement involve fusions of homeologous chromosomes. Females consistently showed a greater degree of recombination.     

Genetic diversity and reproductive mode in two non-native hydromedusae, Maeotias marginata and Moerisia sp., in the upper San Francisco Estuary, California

Reproductive strategy can play a significant role in invasion success and spread. Asexual and sexual reproduction may confer different advantages and disadvantages to a founding population, resulting in varying impacts on genetic diversity and the ability to invade. We investigate the role of reproductive mode in two species of non-native hydromedusae (Maeotias marginata and Moerisia sp.) in the San Francisco Estuary (SFE). Both species can reproduce asexually and sexually. We employed 7?C8 microsatellite markers to determine overall genetic diversity and to investigate contributions of asexual and sexual reproduction to the populations. We found both species had high levels of genetic diversity (Average H_E?=?0.63 and 0.58, Number individuals sampled?=?111 and 277, for M. marginata and Moerisia sp. respectively) but also detected multiple individuals in clonal lineages. We identified the same clones across sampling locations and time, and the index of asexual reproduction (R) was 0.89 for M. marginata and 0.91 for Moerisia sp. Our results suggest both species maintain high population genetic diversity through sexual reproduction, in combination with asexual reproduction, which allows rapid propagation. In addition, we conducted genetic sequence analyses at the ribosomal ITS1 marker, using samples of Moerisia sp. from the SFE and M. lyonsi from Chesapeake Bay. We found 100?% sequence similarity showing that Moerisia sp. in the SFE and Chesapeake Bay are the same species. The two hydromedusae studied here possess the means to propagate rapidly and have high genetic diversity, both of which may allow them to successfully adapt to changing environments and expand their invasions.     

Mutualism Disruption Threatens Global Plant Biodiversity: A Systematic Review

Background

As global environmental change accelerates, biodiversity losses can disrupt interspecific interactions. Extinctions of mutualist partners can create “widow” species, which may face reduced ecological fitness. Hypothetically, such mutualism disruptions could have cascading effects on biodiversity by causing additional species coextinctions. However, the scope of this problem – the magnitude of biodiversity that may lose mutualist partners and the consequences of these losses – remains unknown.

Methodology/Principal Findings

We conducted a systematic review and synthesis of data from a broad range of sources to estimate the threat posed by vertebrate extinctions to the global biodiversity of vertebrate-dispersed and -pollinated plants. Though enormous research gaps persist, our analysis identified Africa, Asia, the Caribbean, and global oceanic islands as geographic regions at particular risk of disruption of these mutualisms; within these regions, percentages of plant species likely affected range from 2.1–4.5%. Widowed plants are likely to experience reproductive declines of 40–58%, potentially threatening their persistence in the context of other global change stresses.

Conclusions

Our systematic approach demonstrates that thousands of species may be impacted by disruption in one class of mutualisms, but extinctions will likely disrupt other mutualisms, as well. Although uncertainty is high, there is evidence that mutualism disruption directly threatens significant biodiversity in some geographic regions. Conservation measures with explicit focus on mutualistic functions could be necessary to bolster populations of widowed species and maintain ecosystem functions.