No abstract

The nematophagous fungus Lecanicillium psalliotae (syn. Verticillium psalliotae) is a well-known biocontrol agent. In this study, a chitinase gene Lpchi1 was isolated for the first time from L. psalliotae using degenerate primers and DNA-walking technique. The cloned gene Lpchi1 encoding 423 amino acid residues shares a high degree of homology with other pathogenicity-related chitinases from entomopathogenic and mycoparasitic fungi. The complementary DNA sequence of the mature chitinase was amplified via reverse transcription polymerase chain reaction and expressed well in Pichia pastoris GS115. Through gel filtration, the recombinant chitinase was purified as a protein of ca. 45 kDa with an optimal activity at pH 7.0 and 37.6 degrees C. The purified chitinase LPCHI1 was found degrading chitinous components of eggs of the root-knot nematode Meloidogyne incognita and significantly influence its development. Moreover, our results also demonstrate that the protease Ver112 and the chitinase LPCHI1 from the same fungus interacted on the egg infection.

We survey results concerning the spectral properties of limit-periodic operators. The main focus is on discrete one-dimensional Schrödinger operators, but other classes of operators, such as Jacobi and CMV matrices, continuum Schrödinger operators and multi-dimensional Schrödinger operators, are discussed as well.We explain that each basic spectral type occurs, and it does so for a dense set of limit-periodic potentials. The spectrum has a strong tendency to be a Cantor set, but there are also cases where the spectrum has no gaps at all. The possible regularity properties of the integrated density of states range from extremely irregular to extremely regular. Additionally, we present background about periodic Schrödinger operators and almost-periodic sequences.In many cases we outline the proofs of the results we present.

Nematophagous fungi have been used as biological control agents against nematodes parasitic to plants and animals. These fungi can secret subtilisin-like extracellular serine proteases during the infection of nematodes. The expression of these subtilisin-like serine proteases is regulated by nitrogen sources, including nematode cuticle. However, the mechanisms underlying the nitrogen sources-induced expression of these serine proteases is not well understood. In this study, we investigated the effect of nitrogen sources on the expression of a subtilisin-like extracellular protease, prC, in the nematophagous fungus Clonostachys rosea. Disruption of prC attenuated infection of the fungus to nematodes, indicating that this gene functions as a virulence factor. The inhibition of basal expression of prC by the preferred nitrogen sources (glutamine, ammonia) occurred at the transcriptional level. In contrast, nematode cuticle induced the expression of prC at the post-transcriptional level. The inducible expression of prC by nematode cuticle was significantly suppressed by glutamine, ammonia and phenylmethylsulfonyl fluoride (an inhibitor of serine protease). Thus, the existence of active PrC, albeit at a low level in the medium, is probably essential for further induction of this gene by nematode cuticle. Moreover, the low molecule weight (< 3 kD) degradation products of nematode cuticle could significantly induce the expression of prC. Ammonia suppresses the virulence of C. rosea against nematodes, probably by inhibiting prC expression. Thus, the nematophagous fungi probably could not function well as biocontrol agents in fields fertilized with a large amount of ammonium salt.

We exhibit limit-periodic Schrödinger operators that are uniformly localized in the strongest sense possible. That is, for these operators there are uniform exponential decay rates such that every element of the hull has a complete set of eigenvectors that decay exponentially off their centers of localization at least as fast as prescribed by the uniform decay rate. Consequently, these operators exhibit uniform dynamical localization.