Rhombomere formation and hind-brain crest cell migration from prorhombomeric origins in mouse embryos

Prior to rhombomere development, structures called prorhombomeres appear in the mammalian hindbrain. This study clarifies the developmental relationship between prorhombomeres and their descendent rhombomeres and hindbrain crest cells in mouse embryos by focal dye injections at various levels of prorhombomere A (proRhA), proRhB, and proRhC, as well as at their boundaries. ProRhA gives rise to two rhombomeres, rhombomeres 1 and 2 (r1 and r2), as well as to crest cells that migrate into the first pharyngeal arch, including the trigeminal ganglion. ProRhB develops into r3 and r4 and produces crest cells populating the second arch and acousticofacial ganglion. The anterior portion of proRhC gives rise to r5 and r6 and to crest cells migrating into the third pharyngeal arch and the IXth ganglion; its posterior portion develops into r7 and releases crest cells into the fourth pharyngeal arch region as well as the Xth ganglion. These results suggest that the boundaries between prorhombomeres serve as lineage restrictions for both hind-brain neuroepithelial cells and for segmental origins of crest cell populations in mouse embryos. The Hox code of the mouse head can be schematized in a much simpler way based on this prorhombomeric organization of the hind-brain, suggesting that prorhombomeres primarily underlie mammalian hind-brain segmentation.     

Non-systemic expression of a stress-responsive maize polyubiquitin gene (Ubi-1) in transgenic rice plants

We have used the promoter, 1st exon and 1st intron of the maize polyubiquitin gene (Ubi-1) for rice transformation experiments and revealed the characteristic expression of Ubi-1 gene: (1) Ubi-1 gene is not regulated systemically but rather individual cells respond independently to the heat or physical stress; (2) Ubi-1 gene changes its tissue-specific expression in response to stress treatment; (3) the expression of Ubi-1 gene is dependent on cell cycle.     

Lamina-specific localization of silicon accumulation in two broadleaf tree species

Journal of Plant Research - Silicon (Si) accumulation differs greatly among plant species, as revealed by an increasing number of studies reporting whole-leaf Si concentration for a wide range of...     

Purification, characterization, cDNA cloning and nucleotide sequencing of a cellulase from the yellow-spotted longicorn beetle, Psacothea hilaris.

A cellulase (endo-beta-1,4-glucanase, EC 3.2.1.4) was purified from the gut of larvae of the yellow-spotted longicorn beetle Psacothea hilaris by acetone precipitation and elution from gels after native PAGE and SDS/PAGE with activity staining. The purified protein formed a single band, and the molecular mass was estimated to be 47 kDa. The purified cellulase degraded carboxymethylcellulose (CMC), insoluble cello-oligosaccharide (average degree of polymerization 34) and soluble cello-oligosaccharides longer than cellotriose, but not crystalline cellulose or cellobiose. The specific activity of the cellulase against CMC was 150 micro mol.min-1.(mg protein)-1. TLC analysis showed that the cellulase produces cellotriose and cellobiose from insoluble cello-oligosaccharides. However, a glucose assay linked with glucose oxidase detected a small amount of glucose, with a productivity of 0.072 micro mol.min-1.(mg protein)-1. The optimal pH of P. hilaris cellulase was 5.5, close to the pH in the midgut of P. hilaris larvae. The N-terminal amino-acid sequence of the purified P. hilaris cellulase was determined and a degenerate primer designed, which enabled a 975-bp cDNA clone containing a typical polyadenylation signal to be obtained by PCR and sequencing. The deduced amino-acid sequence of P. hilaris cellulase showed high homology to members of glycosyl hydrolase family 5 subfamily 2, and, in addition, a signature sequence for family 5 was found. Thus, this is the first report of a family 5 cellulase from arthropods.     

Analysis of randomly isolated cDNAs from developing endosperm of rice (Oryza sativa L.): evaluation of expressed sequence tags,and expression levels of mRNAs

Using a cDNA library prepared from poly(A)⁺ RNA from 10-day-old rice endosperm, partial nucleotide sequences of randomly isolated clones were analyzed. A total of 153 (30.6%) out of 500 cDNA clones showed high amino acid identity to previously identified genes. There was significant redundancy in cDNAs encoding prolamine and glutelin. About 21.0% of the cDNA clones were found to code for seed storage protein genes. Consequently, 37 independent genes were identified. Using cDNA clones encoding glutelin, prolamine, seed allergen, -1,4-glucan branching enzyme, glycine-rich RNA binding protein, metallothionein, non-specific lipid-transfer protein and ubiquitin conjugating enzyme the accumulation of mRNA during rice seed development was compared. Genes associated with seed storage protein and starch biosynthesis were expressed according to expected developmental stages. Glycinerich RNA binding protein genes as well as metallothionein-like protein genes were highly expressed in developing seeds, but low in leaves of whole plants.     

Non-random distribution of transduction termini in transductants from the integrated R plasmid, R100-1

Summary Tra ⁺and tra ^–derivatives of drug resistance plasmid, R100-1, were isolated by phage P1 from an Hfr donor with integrated R100-1 and then analyzed by complementation tests with tra ^–point mutants of Flac. Tra ⁺derivatives of R100-1 carrying tetracycline resistance alone and those carrying all six drug-resistance genes could support transfer of tra ^–point mutants of Flac except Flac traJ, whereas all of tra ^–derivatives of R100-1 failed to complement any one of tra ^–point mutants of Flac. This suggests that these tra ^–derivatives of R100-1 carrying tetracycline resistance gene are deleted for all the transfer genes impaired in the Flac point mutants tested. We assume a hot point, probably a specific base sequence similar to an IS element, at the left of the tetracycline gene (Fig. 1) becomes a transduction terminus in transduction of the integrated R100-1 by phage P1. Complementation analysis of tra ^–derivatives carrying five resistance genes except the tetracycline gene led us to a supposition that a gene(s), probably analogous to traJ of the F plasmid, is located on R100-1 near the tetracycline gene which plays an important regulatory role for self-transfer as well as for the complementation of tra ^–Flac mutants.     

Purification and partial characterization of cytochrome b5 from Tetrahymena pyriformis

With the use of detergents and successive column chromatographies, Tetrahymena b-type cytochrome was purified from microsomes to a specific content of 36.0 nmol per mg of protein. The purified form showed a single band on SDS-polyacrylamide gel with molecular weight of 22,000. The spectral properties of the reduced b-type cytochrome, the α-peak of which is situated at 560 nm and asymmetric with a shoulder at 556 nm, was different from that of rat liver microsomal cytochrome b₅. However, it was reducible by NADH in the presence of NADH-cytochrome b₅ reductase purified from rat liver microsomes.The results indicated that the microsomal b-type cytochrome should be designated as cytochrome b₅ of a ciliated protozoan, Tetrahymena pyriformis.     

Nontranslation of foreign genetic information for fraction 1 protein under circumstances favorable for direct transfer ofNicotiana gossei isolated chloroplasts intoN. Tabacum protoplasts

Summary The nuclei and cytoplasm ofN. gossei andN. tabacum are compatible to the extent that reciprocal, interspecific F₁ hybrids can be produced by conventional breeding techniques. Conditions were established in which manyN. gossei isolated chloroplasts could be seen by phase and fluorescence microscopy to adhere to 40% of the population of protoplasts obtained from white tissue of variegatedN. tabacum plants and to remain attached after washing the protoplasts. Chloroplasts also could be seen to enter the interior of the protoplasts. After treating albino protoplasts withN. gossei chloroplasts, the protoplasts were subjected to further conditions whereby 65 calluses containing shoots developed. TwentyN. tabacum protoplasts not treated with foreign chloroplasts also produced calluses with shoots to serve as a control. All calluses developed chlorophyll irrespective of whether or not the albino protoplasts had been treated with isolatedN. gossei chloroplasts. The Fraction 1 protein ofN. tabacum has a different electrophoretic mobility from the protein ofN. gossei or anN. gossei xN. tabacum F₁ hybrid. The Fraction 1 protein large subunit is coded by chloroplast DNA, whereas the small subunit is coded by nuclear DNA. Fraction 1 protein was isolated from the variegated shoots of the 65 calluses obtained after treating albino protoplasts with foreign chloroplasts. Immunoelectrophoresis demonstrated the protein from each callus to have a mobility identical toN. tabacum protein. Therefore, under circumstances highly favorable for the direct transfer ofN. gossei isolated chloroplasts (and possibly nuclei also) intoN. tabacum protoplasts, no evidence was obtained to suggest that genetic information contained in the isolated foreign organelles was being translated into the polypeptides of either the large or small subunits of Fraction 1 protein contained in newly differentiated leaves derived from the protoplasts. Supported by Research Grant PCM-75-07368 from the National Science Foundation.