Local expression of enzymatically active class I beta-1, 3-glucanase enhances symptoms of TMV infection in tobacco.

Mutant tobacco plants deficient for class I beta-1,3-glucanase (GLU I) are decreased in their susceptibility to virus infection. This is correlated with delayed virus spread, a reduction in the size exclusion limit of plasmodesmata and increased cell-wall deposition of the beta-1,3-glucan callose. To further investigate a role of GLU I during cell-to-cell movement of virus infection, we inserted the GLU I coding sequence into TMV for overexpression in infected cells. Compared with the size of local lesions produced on plants infected with virus expressing either an enzymatically inactive GLU I or a frameshift mutant of the gene, the size of local lesions caused by infection with virus expressing active GLU I was consistently increased. Viruses expressing antisense GLU I constructs led to lesions of decreased size. Similar effects were obtained for virus spread using plants grown at 32 degrees C to block the hypersensitive response. Together, these results indicate that enzymatically active GLU I expressed in cells containing replicating virus can increase cell-to-cell movement of virus. This supports the view that GLU I induced locally during infection helps to promote cell-to-cell movement of virus by hydrolyzing callose. Moreover, our results provide the first direct evidence that a biological function of a plant beta-1,3-glucanase depends on its catalytic activity.

Ethynylogization of a coarctate fragmentation

Coarctate reactions form a separate class of elementary closed-shell processes in addition to polar and pericyclic reactions. Hence, they also follow a different homology principle. Whereas vinylogous polar and pericyclic reactions differ in the length of the reacting system by a double bond, coarctate reactions can be homologized (ethynylogized) by extending a known system by a triple bond. The prediction, which is based on theoretical considerations, is confirmed experimentally by the fragmentation of cyclopropylethynyl nitrene to cyano acetylene and ethylene, a reaction that is "ethynyloguous" to the known fragmentation of cyclopropyl nitrene to ethylene and HCN.

The movement protein NSm of tomato spotted wilt tospovirus (TSWV): RNA binding, interaction with the TSWV N protein, and identification of interacting plant proteins.

The nonstructural NSm protein of tomato spotted wilt tospovirus (TSWV) represents a putative viral movement protein involved in cell-to-cell movement of nonenveloped ribonucleocapsid structures. To study the molecular basis of NSm function, we expressed the protein in Escherichia coli and investigated protein-protein and protein-RNA interactions of NSm protein in vitro. NSm specifically interacts with TSWV N protein and binds single-stranded RNA in a sequence-nonspecific manner. Using NSm as a bait in a yeast two-hybrid screen, we identified two homologous NSm-binding proteins of the DnaJ family from Nicotiana tabacum and Arabidopsis thaliana.

A system to efficiently maintain embryonic lethal mutations in the flour beetle Tribolium castaneum.

Due to its small size, short life cycle, and easy maintenance, the flour beetle Tribolium castaneum is well suited for the genetic analysis of development. One drawback of Tribolium as a genetic system is, however, the difficulty of keeping embryonic lethal lines. Presently, only few lethal mutations can be kept as balanced stocks. Therefore, heterozygous carriers must be identified anew in every generation in order to maintain a recessive embryonic mutation. To alleviate this problem we have devised a block system that allows the simultaneous processing of many mutant lines or test crosses for visual inspection of larval cuticle phenotypes. Using this technique, one person can maintain about 100 embryonic lethal stocks, which makes feasible the thorough genetic analysis of embryogenesis in this species.

Pair-rule and gap gene mutants in the flour beetle Tribolium castaneum.

Early pattern formation in the Drosophila embryo occurs in a syncytial blastoderm where communication between nuclei is unimpeded by cell walls. During the development of other insects, similar gene expression patterns are generated in a cellular environment. In Tribolium, for instance, pair-rule stripes are transiently expressed near the posterior end of the growing germ band. To elucidate how pattern formation in such a situation deviates from that of Drosophila, functional data about the genes involved are essential. In a genetic screen for Tribolium mutants affecting the larval cuticle pattern, we isolated 4 mutants (from a total of 30) which disrupt segmentation in the thorax and abdomen. Two of these mutants display clear pair-rule phenotypes. This demonstrates that not only the expression, but also the function of pair-rule genes in this short-germ insect is in principle similar to Drosophila. The other two mutants appear to identify gap genes. They provide the first evidence for the involvement of gap genes in abdominal segmentation of short-germ embryos. However, significant differences between the phenotypes of these mutants and those of known Drosophila gap mutants exist which indicates that evolutionary changes occurred in either the regulation or action of these genes.

Acute primary human immunodeficiency virus type 1 infection in a patient with concomitant cytomegalovirus encephalitis.

We report what we believe is the first case of primary human immunodeficiency virus type 1 (HIV-1) infection and simultaneous cytomegalovirus (CMV) encephalitis, which was confirmed by detection of CMV DNA in the patient's cerebrospinal fluid with use of the polymerase chain reaction. This coinfection had an unusual course, and the patient's clinical status deteriorated despite administration of combination antiretroviral therapy. The patient responded clinically only after therapy for CMV infection was added to his combination antiretroviral regimen. An atypical course and duration of symptomatic primary HIV-1 infection should suggest a possible coincident infection with other opportunistic agents that are normally expected to cause disease later in the course of HIV-1 infection. Current recommendations from the Centers for Disease Control and Prevention list CMV encephalitis as an AIDS-defining event.