Nodulation gene regulation and quorum sensing control density-dependent suppression and restriction of nodulation in the Bradyrhizobium japonicum-soybean symbiosis

The nodulation of Glycine max cv. Lambert and the nodulation-restricting plant introduction (PI) genotype PI 417566 by wild-type Bradyrhizobium japonicum USDA110 is regulated in a population-density-dependent manner. Nodulation on both plant genotypes was suppressed (inhibited) when plants received a high-density inoculum (10(9) cells/ml) of strain USDA110 grown in complex medium, and more nodules were produced on plants receiving a low-cell-density inoculum (10(5) cells/ml). Since cell-free supernatants from strain USDA110 grown to high cell density in complex medium decreased the expression of an nodY-lacZ fusion, this phenomenon was attributed to bradyoxetin-induced repression of nod gene expression. Inoculation of either the permissive soybean genotype (cv. Lambert) or PI 417566 with 10(9) cells/ml of the nodD2, nolA, nodW, and nwsB mutants of USDA110 enhanced nodulation (up to 24%) relative to that seen with inoculations done with 10(5) cells/ml of the mutants or the wild-type strain, indicating that these genes are involved in population-density-dependent nodulation of soybeans. In contrast, the number of nodules produced by an nodD1 mutant on either soybean genotype was less than those seen with the wild-type strain inoculated at a low inoculum density. The nodD2 mutant outcompeted B. japonicum strain USDA123 for nodulation of G. max cv. Lambert at a high or low inoculum density, and the results of root-tip-marking and time-to-nodulate studies indicated that the nolA and nodD2 mutants nodulated this soybean genotype faster than wild-type USDA110. Taken together, the results from these studies indicate that the nodD2 mutant of B. japonicum may be useful to enhance soybean nodulation at high inoculum densities and that NodD2 is a key repressor influencing host-controlled restriction of nodulation, density-dependent suppression of nodulation, perception of bradyoxetin, and competitiveness in the soybean-B. japonicum symbiosis.     

Molecular cloning and sequencing of porcine<Emphasis Type="Italic"> C5</Emphasis> gene and its association with immunological traits

The complement system helps in the lysis of invading pathogens and modulates the inflammatory as well as the humoral and cellular immune responses. C5 mediates many potent inflammatory and cytolytic events after proteolytic activation by complement convertase enzymes. Hence, to investigate the role of pig C5 (pC5) as a candidate gene for disease resistance in pigs, the complete cDNA of pC5 was sequenced, screened for single nucleotide polymorphisms (SNPs), and an association analysis with various immunological parameters measured in F2 animals of a pig resource population based on a cross of Duroc and Berlin miniature pigs (DUMI) was carried out. In total, 5,422 bp of pC5 cDNA was sequenced, which codes for the 1,677-amino-acid precursor of C5. Four polymorphic sites were detected, one of which was segregating in the DUMI population in three genotypic patterns: AA, AC and CC. Classical (CH50) and alternative (AH50) complement activities, C3c levels, haptoglobin (HP) acute phase protein levels, and antibody titers against Mycoplasma (Mk) and Aujesky (ADV) vaccines were measured in the resource population. Association analysis between C5 and the immunological parameters was carried out using repeated measures mixed and general linear model analysis. The homozygote AA was found to be significantly different from the other two genotypes with respect to AH50 and CH50, whereas genotype CC was found to be significantly different from the other genotypes for C3c and HP levels. No significant difference could be seen between genotypes for antibody titers against vaccinations. Association of C5 with complement activity traits and acute phase proteins promotes pC5 as a candidate gene for innate disease resistance.Nucleotide sequence data reported are available in GenBank database under the accession numbers AY332748 and AY349423     

Association of corticotropin-releasing hormone gene variation with performance and meat quality traits in commercial pig lines

The porcine corticotropin-releasing hormone(CRH) gene is a functional-positional candidate for quantitative tract loci on porcine chromosome 4 with major effects on growth and carcass composition. In addition, the central role of CRH in the neuroendocrine response to stress implicates the CRH gene as a functional candidate for meat quality. Association of a single nucleotide polymorphism (SNP) in the promoter region of the porcine CRH gene (g.233C > T) with several growth, carcass and meat quality traits was examined using more than 2000 individuals from four commercial lines: German Landrace (LR), Pietrain (Pi), German Large White x German Landrace (F1) and the German commercial fattening pig cross of Pietrain x F1 (PiF1). Significant association of the CRH SNP was found with feed conversion ratio in the PiF1 line, with carcass length in the LR line and with lean content in the F1, LR and Pi lines. Moreover, significant association with meat colour was found in the Pi and LR lines; however, the effects were in opposite directions. The presented results indicate that sequence variation in the porcine CRH gene has no major effect on growth and carcass composition in commercial pig lines, although it may significantly contribute to variation in meat quality. The g.233C>T SNP may be in incomplete linkage disequilibrium with causal mutations and/or exhibit effects in the context of DNA variation at other interacting loci.     

Identification of ricinoleic acid as an inhibitor of Ca2+ signal-mediated cell-cycle regulation in budding yeast

Free fatty acids exhibit diverse biological effects such as the regulation of immune responses in humans and animals. To investigate the biological effect of fatty acids in the model eukaryotic organism yeast, we examined the activity of various fatty acids in a yeast-based drug-screening system designed to detect the small-molecule compounds that inhibit Ca²⁺-signal-mediated cell-cycle regulation. Among the fatty acids examined, ricinoleic acid markedly alleviated the deleterious physiological effects induced by the compelled activation of Ca²⁺ signaling by external CaCl₂, such as the polarized bud growth and the growth arrest in the G₂ phase. In accordance with the physiological consequences induced by ricinoleic acid, it diminished the Ca²⁺-induced phosphorylation of Cdc28p at Tyr-19, concomitant with the decrease in the Ca²⁺-stimulated expression levels of Cln2p and Swe1p.     

Mapping of quantitative trait loci for mycoplasma and tetanus antibodies and interferon-gamma in a porcine F2 Duroc × Pietrain resource population

The aim of the present study was to detect quantitative trait loci (QTL) for innate and adaptive immunity in pigs. For this purpose, a Duroc × Pietrain F₂ resource population (DUPI) with 319 offspring was used to map QTL for the immune traits blood antibodies and interferon-gamma using 122 microsatellites covering all autosomes. Antibodies response to Mycoplasma hyopneumoniae and tetanus toxoid vaccine and the interferon-gamma (IFNG) serum concentration were measured at three different time points and were used as phenotypes. The differences of antibodies and interferon concentration between different time points were also used for the linkage mapping. Line-cross and imprinting QTL analysis, including two-QTL, were performed using QTL Express. A total of 30 QTL (12, 6, and 12 for mycoplasma, tetanus antibody, and IFNG, respectively) were identified at the 5% chromosome-wide-level significant, of which 28 were detected by line-cross and 2 by imprinting model. In addition, two QTL were identified on chromosome 5 using the two-QTL approach where both loci were in repulsion phase. Most QTL were detected on pig chromosomes 2, 5, 11, and 18. Antibodies were increased over time and immune traits were found to be affected by sex, litter size, parity, and month of birth. The results demonstrated that antibody and IFNG concentration are influenced by multiple chromosomal areas. The flanking markers of the QTL identified for IFNG on SSC5 did incorporate the position of the porcine IFNG gene. The detected QTL will allow further research in these QTL regions for candidate genes and their utilization in selection to improve the immune response and disease resistance in pig.