Novel induced mlo mutant alleles in combination with site-directed mutagenesis reveal functionally important domains in the heptahelical barley Mlo protein

<p>Abstract</p> <p>Background</p> <p>Recessively inherited natural and induced mutations in the barley <it>Mlo </it>gene confer durable broad-spectrum resistance against the powdery mildew pathogen, <it>Blumeria graminis </it>f.sp. <it>hordei</it>. <it>Mlo </it>codes for a member of a plant-specific family of polytopic integral membrane proteins with unknown biochemical activity. Resistant barley <it>mlo </it>mutant alleles identify amino acid residues that are critical for Mlo function in the context of powdery mildew susceptibility.</p> <p>Results</p> <p>We molecularly analyzed a novel set of induced barley <it>mlo </it>mutants and used site-directed mutagenesis in combination with transient gene expression to unravel novel amino acid residues of functional significance. We integrate these results with previous findings to map functionally important regions of the heptahelical Mlo protein. Our data reveal the second and third cytoplasmic loop as being particularly sensitive to functional impediment by mutational perturbation, suggesting that these regions are critical for the susceptibility-conferring activity of the Mlo protein. In contrast, only mutations in the second but not the third cytoplasmic loop appear to trigger the Endoplasmic Reticulum-localized quality control machinery that ensures the biogenesis of properly folded membrane proteins.</p> <p>Conclusion</p> <p>Our findings identify functionally important regions of the polytopic barley Mlo protein and reveal the differential sensitivity of individual protein domains to cellular quality control.</p

Molecular diversity, population structure, and linkage disequilibrium in a worldwide collection of tobacco (Nicotiana tabacum L.) germplasm

<p>Abstract</p> <p>Background</p> <p>The goals of our study were to assess the phylogeny and the population structure of tobacco accessions representing a wide range of genetic diversity; identify a subset of accessions as a core collection capturing most of the existing genetic diversity; and estimate, in the tobacco core collection, the extent of linkage disequilibrium (LD) in seven genomic regions using simple sequence repeat (SSR) markers. To this end, a collection of accessions were genotyped with SSR markers. Molecular diversity was evaluated and LD was analyzed across seven regions of the genome.</p> <p>Results</p> <p>A genotyping database for 312 tobacco accessions was profiled with 49 SSR markers. Principal Coordinate Analysis (PCoA) and Bayesian cluster analysis revealed structuring of the tobacco population with regard to commercial classes and six main clades were identified, which correspond to "Oriental", Flue-Cured", "Burley", "Dark", "Primitive", and "Other" classes. Pairwise kinship was calculated between accessions, and an overall low level of co-ancestry was observed. A set of 89 genotypes was identified that captured the whole genetic diversity detected at the 49 loci. LD was evaluated on these genotypes, using 422 SSR markers mapping on seven linkage groups. LD was estimated as squared correlation of allele frequencies (<it>r²</it>). The pattern of intrachromosomal LD revealed that in tobacco LD extended up to distances as great as 75 cM with <it>r²</it>> 0.05 or up to 1 cM with <it>r²</it>> 0.2. The pattern of LD was clearly dependent on the population structure.</p> <p>Conclusions</p> <p>A global population of tobacco is highly structured. Clustering highlights the accessions with the same market class. LD in tobacco extends up to 75 cM and is strongly dependent on the population structure.</p

Mikrobiologie und Bioaktivität des biodynamischen Präparats 500

Umfangreiche mikrobiologische Untersuchungen des Hornmistpräparates zeigen eine charakteristische bakterielle Komposition und spezielle Enzymaktivitäten. Letztere haben eine Wirkung vergleichbar dem pflanzeneigenen Hormon Auxin. P500 scheint die Effizienz der Bodenbakterien zu erhöhen