原生质体诱变选育无孢平菇

用紫外线照射紫孢侧耳(Pleurotus sapidus)双核菌丝原生质体,再生后筛选生长势好的菌株, 通过出菇试验得到了生产性状与紫孢侧耳一致的无孢和少孢平菇新品种。Abstract: This paper reported isolation and regeneration of the dikaryocyte protoplasts from Pleurotus sapidus, and the protoplasts were treated by U.V-irradiation for selection spore less mutants.     

A novel mammalian Ras GTPase-activating protein which has phospholipid-binding and Btk homology regions.

We have previously purified a novel GTPase-activating protein (GAP) for Ras which is immunologically distinct from the known Ras GAPs, p120GAP and neurofibromin (M. Maekawa, S. Nakamura, and S. Hattori, J. Biol. Chem. 268:22948-22952, 1993). On the basis of the partial amino acid sequence, we have obtained a cDNA which encodes the novel Ras GAP. The predicted protein consists of 847 amino acids whose calculated molecular mass, 96,369 Da, is close to the apparent molecular mass of the novel Ras GAP, 100 kDa. The amino acid sequence shows a high degree of similarity to the entire sequence of the Drosophila melanogaster Gap1 gene. When the catalytic domain of the novel GAP was compared with that of Drosophila Gap1, p120GAP, and neurofibromin, the highest degree of similarity was again observed with Gap1. Thus, we designated this gene Gap1m, a mammalian counterpart of the Drosophila Gap1 gene. Expression of Gap1m was relatively high in brain, placenta, and kidney tissues, and it was expressed at low levels in other tissues. A recombinant protein consisting of glutathione-S-transferase and the GAP-related domain of Gap1m stimulated GTPase of normal Ras but not that of Ras having valine at the 12th residue. Expression of the same region in Saccharomyces cerevisiae suppressed the ira2- phenotype. In addition to the GAP catalytic domain, Gap1m has two domains with sequence closely related to those of the phospholipid-binding domain of synaptotagmin and a region with similarity to the unique domain of Btk tyrosine kinase. These results clearly show that Gap1m is a novel Ras GAP molecule of mammalian cells.     

Analysis of RIM11, a yeast protein kinase that phosphorylates the meiotic activator IME1.

Many yeast genes that are essential for meiosis are expressed only in meiotic cells. Known regulators of early meiotic genes include IME1, which is required for their expression, and SIN3 and UME6, which prevent their expression in nonmeiotic cells. We report here the molecular characterization of the RIM11 gene, which we find is required for expression of several early meiotic genes. A close functional relationship between RIM11 and IME1 is supported by two observations. First, sin3 and ume6 mutations are epistatic to rim11 mutations; prior studies have demonstrated their epistasis to ime1 mutations. Second, overexpression of RIM11 can suppress an ime1 missense mutation (ime1-L321F) but not an ime1 deletion. Sequence analysis indicates that RIM11 specifies a protein kinase related to rat glycogen synthase kinase 3 and the Drosophila shaggy/zw3 gene product. Three partially defective rim11 mutations alter residues involved in ATP binding or catalysis, and a completely defective rim11 mutation alters a tyrosine residue that corresponds to the site of an essential phosphorylation for glycogen synthase kinase 3. Immune complexes containing a hemagglutinin (HA) epitope-tagged RIM11 derivative, HA-RIM11, phosphorylate two proteins, p58 and p60, whose biological function is undetermined. In addition, HA-RIM11 immune complexes phosphorylate a functional IME1 derivative but not the corresponding ime1-L321F derivative. We propose that RIM11 stimulates meiotic gene expression through phosphorylation of IME1.     

Human RNaseP RNA and nucleolar 7-2 RNA share conserved ‘To’ antigen-binding domains

RNase P in both prokaryotes and eukaryotes is a ribonucleoprotein that cleaves tRNA precursors to generate the 5 termini of the mature tRNAs. Many patients with autoimmune diseases produce antibodies against a 40 kDa protein (designatedTo orTh antigen) which is an integral component of eukaryotic RNaseP as well as nucleolar 7-2 RNP which is identical to the mitochondrial RNA processing (MRP) RNP. Interestingly, theTo antigen found in human cells and the C5 protein, the only protein component ofE. coli RNaseP, are antigenically related. In this study, we show that a 56 nucleotide-long sequence, corresponding to nucleotides 20–75 near the 5 end of human RNaseP RNA, is sufficient to bind theTo antigen. We previously showed that the humanTo antigen binds to a short distinct structural domain near the 5 end of human 7-2/MRP RNA. There is no obvious primary sequence homology between theTo antigen binding sites in RNaseP RNA and 7-2/MRP RNA; however, these sequences are capable of assuming a similar secondary structure which corresponds to the recently proposed cage structure for RNaseP RNAs and 7-2/MRP RNA (Forster and Altman (1989) Cell 62: 407–409). These data are supportive of the idea that these two RNAs may have evolved from a common progenitor molecule.     

Nitric oxide synthase in the enteric nervous system of the guinea-pig: a quantitative description

The distribution and abundance of nitric oxide synthase (NOS)-containing neurons and their terminals in the gastrointestinal tract of the guinea-pig were examined in detail using NADPH diaphorase histochemistry and NOS immunohistochemistry. NOS-containing cell bodies were found in the myenteric plexus throughout the gastrointestinal tract and in the submucous plexus of the stomach, colon and rectum. NOS-containing neurons comprised between 12% (in the duodenum) and 54% (in the esophagus) of total myenteric neurons. In the ileum, NOS neurons represented 19% of total myenteric neurons. Most of the NOS neurons throughout the gastrointestinal tract possessed lamellar dendrites and a single axon. NOS-containing terminals were abundant in the circular muscle, including that of the sphincters, but were rare in the longitudinal muscle, except for the taeniae of the caecum. The muscularis mucosae of the esophagus, stomach, colon and rectum received a medium to dense innervation by NOS terminals. Within myenteric ganglia, NOS-containing terminals were extremely sparse in the esophagus, stomach and duodenum, common in the ileum and distal colon and extremely dense in the proximal colon and rectum. The submucous plexus in the ileum and large intestine contained a sparse plexus of NOS-containing terminals. NOS terminals were not observed in the mucosa of any region. We conclude that throughout the gastrointestinal tract of the guinea-pig, NOS neurons are inhibitory motor neurons to the circular muscle; in the ileum and large intestine, NOS neurons may also function as interneurons.