Three genes that contribute to the ability of the fungus Nectria haematococca to cause disease on pea plants have been identified. These pea pathogenicity (PEP) genes are within 25 kb of each other and are located on a supernumerary chromosome. Altogether, the PEP gene cluster contains six transcriptional units that are expressed during infection of pea tissue. The biochemical function of only one of the genes is known with certainty. This gene, PDA1, encodes a specific cytochrome P450 that confers resistance to pisatin, an antibiotic produced by pea plants. The three new PEP genes, in addition to PDA1, can independently increase the ability of the fungus to cause lesions on pea when added to an isolate lacking the supernumerary chromosome. Based on predicted amino acid sequences, functions for two of these three genes are hypothesized. The deduced amino acid sequence of another transcribed portion of the PEP cluster, as well as four other open reading frames in the cluster, have a high degree of similarity to known fungal transposases. Several of the features of the PEP cluster -- a cluster of pathogenicity genes, the presence of transposable elements, and differences in codon usage and GC content from other portions of the genome -- are shared by pathogenicity islands in pathogenic bacteria of plants and animals.

Background: China's coastal wetlands belong to some of the most threatened ecosystems worldwide. The loss and degradation of these wetlands seriously threaten waterbirds that depend on wetlands.

Recent studies have shown that recombinant adeno-associated virus (rAAV) can persist in episomal form; however, factors affecting rAAV persistence are poorly understood. DNA-dependent PK (DNA-PK) is a DNA repair enzyme, which we previously found played an important role in determining the molecular fate of the rAAV genome in mouse skeletal muscle. In the present study, we tested the effect of DNA-PK on AAV serotype 2 integration in vitro and in vivo in mouse liver. In an in vitro integration system, addition of DNA-PK decreased AAV integration, whereas antibody against DNA-PKcs increased integration. In vivo, matched doses of a recombinant AAV serotype 2 vector were injected into the portal vein of either C57BL͞6 (DNA-PKcs ؉/؉ ) or severe combined immunodeficient (DNA-PKcs ؊/؊ ) mice. After partial hepatectomy to stimulate hepatocyte proliferation, retention of vector genomes and of transgene expression was substantially higher in severe combined immunodeficient mice, indicating that in the absence of DNA-PKcs, a greater proportion of genomes integrated into the cellular genome. In summary, we have provided evidence that DNA-PK inhibits AAV integration both in vitro and in vivo.R ecombinant adeno-associated virus (rAAV) vectors have been increasingly used for gene therapy because they are relatively nontoxic and can mediate long-term transgene expression. Because this vector is used more frequently in clinical trials, it has become crucial to attain an improved understanding of its potential for insertional mutagenesis. Recent studies have shown that the majority of rAAV genomes persist in episomal form after in vivo delivery and that the hallmark of these episomal forms is the production of vector-to-vector junctions, resulting in either circular episomes or high molecular weight concatamers (1-3). Little is known about the cellular factors required for the maturation of rAAV DNA into these stable episomal forms. We previously demonstrated that in skeletal muscle of severe combined immunodeficient (SCID) [DNA-dependent protein kinase catalytic subunit (DNA-PKcs)-negative] mice, some rAAV serotype 2 (rAAV2) genomes persist as linear episomes and then gradually integrate into the cellular genome, whereas in C57BL͞6 (DNA-PKcs-positive) mice, they form circular episomes (2). Most recently, Duan et al. (4) also have shown that SCID skeletal muscle retains both circular and linear forms of rAAV genomes, whereas C57BL͞6 muscle retains only circular forms of rAAV.The DNA-PK is composed of a DNA-binding Ku70͞Ku80 heterodimer and a large catalytic subunit (DNA-PKcs) and functions as a nuclear serine͞threonine protein kinase (5). The Ku protein was first identified as an autoantigen in patients with lupus. It is a heterodimer composed of two tightly associated subunits, Ku70 and Ku80, and is the most abundant DNA end-binding protein in mammalian cells. It recognizes a variety of DNA structures (blunt, overhanging, or hairpin) and binds with high affinity in a DNA sequence-independent manner. In the present studies, we sho...

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Insect-resistant poplar (Populus nigra L.) plants have been produced by infecting leaves with Agrobacterium tumefaciens strains carrying a binary vector containing different truncated forms of a Bacillus thuringiensis (B.t.)toxin gene under a duplicated CaMV 35S promoter. Putative transgenic plants were propagated by cuttings at two experimental farms (in Beijing and Xinjiang, China). At 2-3 years after transformation, 17 of them were selected on the bases of insect-tolerance and good silvicultural traits, and evaluated for insect resistance, for the presence of the B.t. toxin DNA fragment (Southern blots and PCR) and for the expression of the transgene (western and northern blots). Somaelonal variation, as suggested by the appearance of permanent changes in the shape of the leaves, was also investigated with molecular tools (RFLP (restriction fragment length polymorphism), RAPD (random amplified polymorpbic DNA) and microsatellite DNA).Bioassays with Apochemia cineraius and Lymantria dispar on the leaves of the selected clones showed different and, in some cases, high levels of insecticidal activity. The molecular analysis demonstrated integration and expression of the foreign gene. Somatic changes were correlated to extensive genomic changes and were quantified in dendrograms, in terms of genomic similarity. The analysis of control plants suggested that genomic changes were correlated to the in vitro culture step necessary for A. tumefaciens-mediated gene transfer, rather than to the integration of the foreign genes.Three transgenic clones (12, 153 and 192), selected for insect resistance, reduced morphological changes and promising silvicultural traits, are now under large-scale field evaluation in six different provinces in China.

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The evolution and driving factors underlying dust activity in central Asia remain controversial, particularly in its effects on downwind regions. We present a Holocene dust storm activity record retrieved from the Tarim Basin (TB) and perform linear and nonlinear analyses on dust records from the TB and the Greenland areas. The results indicate a similar response of dust activities to total solar irradiance in both areas, and an outbreak of dust storms in the TB at ~3.5 kyr BP. We suggest that decreasing temperature in high northern latitudes, aided by solar activity change, reached a critical threshold near ~3.5 kyr BP. The resulting steepening of the meridional temperature gradient would have facilitated strengthening and southward shift of the Northern Hemisphere westerly jet, leading to the outbreak of dust storms through intensification of low level wind intensity and prolonged spring conditions in the Asian interior.