Analysis of a Plant Complex Resistance Gene Locus Underlying Immune-Related Hybrid Incompatibility and Its Occurrence in Nature

Mechanisms underlying speciation in plants include detrimental (incompatible) genetic interactions between parental alleles that incur a fitness cost in hybrids. We reported on recessive hybrid incompatibility between an Arabidopsis thaliana strain from Poland, Landsberg erecta (Ler), and many Central Asian A. thaliana strains. The incompatible interaction is determined by a polymorphic cluster of Toll/interleukin-1 receptor-nucleotide binding-leucine rich repeat (TNL) RPP1 (Recognition of Peronospora parasitica1)-like genes in Ler and alleles of the receptor-like kinase Strubbelig Receptor Family 3 (SRF3) in Central Asian strains Kas-2 or Kond, causing temperature-dependent autoimmunity and loss of growth and reproductive fitness. Here, we genetically dissected the RPP1-like Ler locus to determine contributions of individual RPP1-like Ler (R1R8) genes to the incompatibility. In a neutral background, expression of most RPP1-like Ler genes, except R3, has no effect on growth or pathogen resistance. Incompatibility involves increased R3 expression and engineered R3 overexpression in a neutral background induces dwarfism and sterility. However, no individual RPP1-like Ler gene is sufficient for incompatibility between Ler and Kas-2 or Kond, suggesting that co-action of at least two RPP1-like members underlies this epistatic interaction. We find that the RPP1-like Ler haplotype is frequent and occurs with other Ler RPP1-like alleles in a local population in Gorzów Wielkopolski (Poland). Only Gorzów individuals carrying the RPP1-like Ler haplotype are incompatible with Kas-2 and Kond, whereas other RPP1-like alleles in the population are compatible. Therefore, the RPP1-like Ler haplotype has been maintained in genetically different individuals at a single site, allowing exploration of forces shaping the evolution of RPP1-like genes at local and regional population scales.

Islands of euchromatin-like sequence and expressed polymorphic sequences within the short arm of human chromosome 21

The goals of the human genome project did not include sequencing of the heterochromatic regions. We describe here an initial sequence of 1.1 Mb of the short arm of human chromosome 21 (HSA21p), estimated to be 10% of 21p. This region contains extensive euchromatic-like sequence and includes on average one transcript every 100 kb. These transcripts show multiple inter- and intrachromosomal copies, and extensive copy number and sequence variability. The sequencing of the "heterochromatic" regions of the human genome is likely to reveal many additional functional elements and provide important evolutionary information.

Scrfl restriction fragment length polymorphism at the D7S23 locus (probe pKM.19), closely linked to cystic fibrosis

Source/Description: pKM.19 is a 1.0 kb EcoRI genomic fragment in pUC13 (ref. 1,2). pPl was isolated independently but contains the same fragment as pKM.19 (ref. 3)...

A polymorphic DNA probe from chromosome 7 (7q22)

Source/Description: p6a-l is a O.9 kb HindIII/BamHl genomic fragment subclone or cosmic cNX.6a in pUC13. cNX.6a was isolated from a non-methylated enriched library from the CMGT cell line Cll (1,2).

Genetic variation in the European hake, Merluccius merluccius. Description of protein loci and genetic divergence between Atlantic and Mediterranean populations = Anàlisi de la variabilitat genètica en el lluç europeu, Merluccius merluccius. Descripció dels loci electroforètics i divergència genètica entre les poblacions atlàntica i mediterrània

We examined the genetic population structure of the european hake (Merluccius merluccius) using electrophoretically detectable population markers in 35 protein loci. Samples were collected from 7 locations in the Atlantic Ocean and Mediterranean Sea. Six loci were polymorphic using the 0.05 criterion of polymorphism. Sample heterozigosities ranged from 0.052 to 0.072 and averaged 0.0625. In this study, significant allele frequency differences were detected between Atlantic and Mediterranean populations in three polymorphic loci: GAPDH-1*, GPI-2* and SOD-1*. Two major genetic groups were considered: a North-Atlantic stock and the Mediterranean stock. The Nei genetic distance, D, (based on 33 loci) between samples from these two groups ranged from 0.002 to 0.006. Genetic differenciation between these areas appears to reflect the barrier effect of Strait of Gibraltar. On average over loci, 96.92 % of the total gene diversity was contained within samples, 0.23 % expressed differences among locations within areas, and 2.64 % differences between regions. A review of morphological variation together with the genetic data presented here suggest that the populations of hake from these areas are subdivided into two different stocks: the North-Atlantic stock and the Mediterranean stock. The most conservative approach to the management of these stocks is to consider the Atlantic and Mediterranean stocks independently from oneanother