Summary Horse domestication revolutionized warfare and accelerated travel, trade, and the geographic expansion of languages. Here, we present the largest DNA time series for a non-human organism to date, including genome-scale data from 149 ancient animals and 129 ancient genomes (≥1-fold coverage), 87 of which are new. This extensive dataset allows us to assess the modern legacy of past equestrian civilizations. We find that two extinct horse lineages existed during early domestication, one at the far western (Iberia) and the other at the far eastern range (Siberia) of Eurasia. None of these contributed significantly to modern diversity. We show that the influence of Persian-related horse lineages increased following the Islamic conquests in Europe and Asia. Multiple alleles associated with elite-racing, including at the MSTN “speed gene,” only rose in popularity within the last millennium. Finally, the development of modern breeding impacted genetic diversity more dramatically than the previous millennia of human management.

The bacterial genera Rhizobium and

Restriction enzyme-mediated DNA integration (REMI) has recently received attention as a new technique for the generation of mutants by transformation in fungi. Here we analyse this method in the basidiomycete Coprinus cinereus using the homologous pabI gene as a selectable marker and the restriction enzymes BamHI, EcoRI and PstI. Addition of restriction enzymes to transformation mixtures results in an earlier appearance of transformants and influences transformation rates in an enzyme- and concentration-dependent manner. Low concentrations of restriction enzyme result in increased numbers of transformation rates decrease with higher enzyme concentrations. If protoplasts are made from cells stored in the cold, the transformation rates drop drastically even in the presence of low amounts of enzyme. In several transformants, plasmid integration directly correlated with the action of restriction enzyme at random chromosomal restriction sites. In some cases, restriction enzymes appear to reduce the number of integration events per transformant. Simultaneously, mutation rates can be enhanced due to the presence of restriction enzymes. Although restriction enzymes clearly promote plasmid integration into the host genome they also have cytotoxic and possibly mutagenic effects that result from processes other than plasmid integration. In consequence, for any given enzyme used in REMI mutagenesis, the enzyme concentration that gives the highest number of transformants must be defined experimentally. Such optimal transformation conditions should give the highest probability of obtaining mutations caused by a single restriction enzyme-mediated integration of the selection marker.

Suspension-cultured cells of tomato (Lycopersicon esculentumMill.) reacted to spores and spore exudates of the pathogen Cladosporium fulvum with a rapid, transient alkalinization of their growth medium that resembled the previously described alkalinization response elicited by chitin fragments (C. Felix, M. Regenass, T. Boller 119931 Plant J 4: 307-316) and was likewise inhibited by the protein kinase inhibitor K-252a. However, the spore factor recognized by the cells differed from chitin fragments in that it was butanol soluble and active in cells refractory to stimulation by chitin fragments. The spore factor was purified and identified as ergosterol, the main sterol of most higher fungi. With pure ergosterol, half-maximal induction was reached at about 1 O PM. After treatment with ergosterol, tomato cells became refractory to a subsequent stimulation by C. fulvum and vice versa, indicating that ergosterol was the principal component of the spores recognized by the plant cells. Most other sterols were inactive, including cholesterol, a range of animal steroid hormones, and all natural plant sterols tested, except for stigmasterol, which was about 106 times less active than ergosterol. Our data demonstrate that tomato cells perceive ergosterol with a selectivity and sensitivity that resembles the perception of steroid hormones in animals.Chemosensory perception of microbial substances plays a major role in the interaction of plants with microbes. Thus, many plants have sensitive and selective perception systems for elicitors derived from pathogenic fungi, which cause the induction of a variety of defense responses (Dixon and Lamb, 1990;Ryan and Farmer, 1991). Oligosaccharides, glycopeptides/glycoproteins, peptides/proteins, and the fatty acid arachidonic acid have been identified as fungal compounds with elicitor activity in various plant systems (Ebel and Scheel, 1992). In addition, plants may also recognize their symbionts by chemical signals, as exemplified by the recognition system of leguminous plants for Nod factors, specific lipochitooligosaccharides produced by symbiotic rhizobia (Fisher and Long, 1992).Changes in plasma membrane properties, including depolarization, efflux of Kf, and alkalinization of the growth medium, are among the earliest responses of plant cells to microbial elicitors (Dixon and Lamb, 1990;Scheel and Parker, 1990;Wei et al., 1992) and endogenous elicitors (Mathieu et al., 1991) as well as to Nod factors (Ehrhardt et al., 1992). In recent work in our laboratory it was observed that washed yeast cell walls induced a rapid alkalinization of the growth medium in suspension-cultured tomato (Lycopersicon esculentum Mill.) cells (Felix et al., 1993). This occurred because enzymes present in the culture medium released chitin fragments from the yeast cell walls, and because the tomato cells had a highly sensitive, specific perception system for the chitin oligosaccharides responsible for the rapid, transient induction of alkalinization. After a first stimulation with chitin fragments, the...

Strains of the phytopathogenic bacterium Pseudomonas syringae pv. syringae secrete a family of structurally closely related peptide derivatives dubbed syringolins, of which syringolin A is the major variant. The function of syringolins in the interaction of P. syringae pv. syringae with their host plants presently is unknown. It is hypothesized that they may constitute virulence factors. However, syringolins are determinants recognized and reacted to by nonhost plant species, and syringolin A has been shown to induce hypersensitive death of cells colonized by powdery mildew in wheat and, thus, to reprogram a compatible interaction into an incompatible one. Syringolin A is an unusual derivative of a tripeptide that contains a 12-membered ring consisting of the amino acids 5-methyl-4-amino-2-hexenoic acid and 3,4-dehydrolysine, two nonproteinogenic amino acids. Here we report the cloning, sequencing, and analysis of genes involved in the biosynthesis of syringolin A. The genes encode proteins consisting of modules typical for nonribosomal peptide synthetases and type I polyketide synthetases, as well as proteins likely involved in the transcriptional regulation of syringolin A biosynthesis and in syringolin A export. The structure and arrangement of the modules lead to the formulation of a model explaining the synthesis of the tripeptide, including the formation of the two nonproteinogenic amino acids in the ring structure of syringolin A.