Biomechanical and Morphometric Differences in Triticum aestivum Seedlings Differing in Rht Gene-Dosage

Biomechanical and morphometric comparisons among coleoptilesfrom wheat seedlings differing in Rht gene-dosage (Rht = 0,2, 4 doses) are presented in an effort to evaluate the influenceof Rht on the mechanics of soil penetration by this organ. Rhtis known to reduce seedling establishment compared to the wildtype. Data from 3–7-day-old seedlings indicate that Rhtreduces tissue elastic modulus E, increases the second momentof area I, and decreases the slenderness ratio (l/r) of coleoptiles.Rht-relatedchanges in E and I are such that the flexural stiffness of coleoptilesfrom Rht plants does not differ significantly from the wildtype-hence the growing coleoptiles of all three genotypes haveequivalent biomechanical capacity to penetrate the soil. Rhtreduction of coleoptile slenderness ratios confers a capacityto safely sustain higher axial compressive loads compared tocoleoptiles with equivalent flexural stiffness but higher ratios.However, wild type seedlings produce longer coleoptiles andlonger subcrown internodes than Rht seedlings. Longer coleoptilesdeliver the crown node closer to the top of the soil beforethe crown node extends beyond the lateral confinement of thecoleoptile. This reduces the potential for buckling of the subcrowninternode and leaves due to the compressive loading of soil.Rht affects a variety of mechanical features whose influenceis dependent upon the stage of seedling growth and the degreeof soil compaction. However, at equivalent depths of burialwhich exceed the maximum length of coleoptiles and moderatesoil compaction, Rht is biomechanically disadvantageous to seedlingestablishment. Wheat, germination, biomechanics, Rht-gene     

Human Dendritic Cell DC-SIGN and TLR-2 Mediate Complementary Immune Regulatory Activities in Response to Lactobacillus rhamnosus JB-1

The microbiota is required for optimal host development and ongoing immune homeostasis. Lactobacilli are common inhabitants of the mammalian large intestine and immunoregulatory effects have been described for certain, but not all, strains. The mechanisms underpinning these protective effects are beginning to be elucidated. One such protective organism is Lactobacillus rhamnosus JB-1 (Lb. rhamnosus JB-1). Lb. murinus has no such anti-inflammatory protective effects and was used as a comparator organism. Human monocyte-derived dendritic cells (MDDCs) were co-incubated with bacteria and analysed over time for bacterial adhesion and intracellular processing, costimulatory molecule expression, cytokine secretion and induction of lymphocyte polarization. Neutralising antibodies were utilized to identify the responsible MDDC receptors. Lb. rhamnosus JB-1 adhered to MDDCs, but internalization and intracellular processing was significantly delayed, compared to Lb. murinus which was rapidly internalized and processed. Lb. murinus induced CD80 and CD86 expression, accompanied by high levels of cytokine secretion, while Lb. rhamnosus JB-1 was a poor inducer of costimulatory molecule expression and cytokine secretion. Lb. rhamnosus JB-1 primed MDDCs induced Foxp3 expression in autologous lymphocytes, while Lb. murinus primed MDDCs induced Foxp3, T-bet and Ror-γt expression. DC-SIGN was required for Lb. rhamnosus JB-1 adhesion and influenced IL-12 secretion, while TLR-2 influenced IL-10 and IL-12 secretion. Here we demonstrate that the delayed kinetics of bacterial processing by MDDCs correlates with MDDC activation and stimulation of lymphocytes. Thus, inhibition or delay of intracellular processing may be a novel strategy by which certain commensals may avoid the induction of proinflammatory responses.     

Novel Plasmids from Alkaliphilic Halomonads

Seventeen alkaliphilic halomonads were examined for the presence of plasmids. Of these, eight strains harbored one or more from 5.3 to 33 kb in size, the first plasmids to be identified from an alkaliphilic halomonad source. Restriction and hybridization analysis revealed three strains that maintained an identical 5.9-kb plasmid which we named pAH1, two that had an identical 33-kb plasmid, and three others, of which one carried two plasmids of 5.3 and 15 kb, the former being designated pAH2. The two final strains maintained plasmids of 15 and 20.5 kb. Restriction mapping of both pAH1 and pAH2 indicated that they have a number of unique restriction sites and are of a small enough size to make them suitable for vector construction.     

Genetic analysis of replicating instabilities in yeast

Strains showing ethyl methanesulfonate (EMS)-induced replicating instability were genetically analysed to test whether within a given line, mosaics from different plating generations carry a mutation at the same site within the locus. A forward mutation system involving five loci controlling adenine biosynthesis in Schizosaccharomyces pombe was used. Genetic analysis was carried out by interallelic complementation and intragenic recombination tests. The data showed that EMS-induced instabilities are site-specific in being confined to the same recombination unit. This finding is discussed in relation to the possible mechanism(s) of replicating instabilities after different mutagenic treatments in a variety of biological systems.