Developmental profiles of wing imaginal discs of flügellos(fl), a wingless mutant of the silkworm, Bombyx mori

 Mutations at the flügellos (fl) locus in Bombyx mori give rise to wingless pupae and moths. To understand the developmental steps responsible for the fl wing defect, we compared the morphological changes and protein synthesis profiles between fl and wild-type (WT) wing discs during larval development. Morphologically, the four wing discs in the fl homozygote larva developed normally at least until the fourth instar, but they were slightly smaller than those of the WT. After the last larval ecdysis, wing epithelial invagination and tracheal migration into the lacunar spaces evidently occurred in the WT wing discs. However, there was no apparent morphological change in fl discs through the fifth instar. The fl wing discs cultured in medium containing 20-hydroxyecdysone (20E) did not grow and develop, although the WT wing discs extended and differentiated under the same conditions. A comparison of protein synthesis in the wing discs revealed that several bands were differentially expressed between the fl and WT. A 41-kDa band expressed abundantly from larval to pharate pupal stages in the WT wing discs was rarely observed in fl discs. Furthermore, in vitro culture studies showed that the 41-kDa protein was induced by 20E and specifically synthesized in WT wing discs after the wandering stage, but not in fl discs. The wing-specific protein synthesis and morphogenesis in fl wing discs may be blocked due to aberrant expression of the fl gene. Received: 6 November 1996 / Accepted: 5 February 1997     

Identification of the Sites for Suppressor Mutations on the Hemagglutinin Molecule to Temperature-Sensitive Phenotype of the Influenza Virus

A temperature-sensitive (ts) mutant of the influenza virus A/WSN/ 33 strain, ts-134, possessed a defect in intracellular transport at the nonpermissive temperature and marked thermolability of hemagglutinin (HA) activity at 51 C. These were caused by a change at amino acid residue 157 from tyrosine to histidine in the HA protein. We isolated 37 spontaneous revertant clones from ts-134 at the nonpermissive temperature and determined their HA sequences. The deduced amino acid sequences demonstrated that one was a true revertant and the others were revertants with suppressor mutations, each of which had an additional amino acid change besides those of ts-134. The changed amino acids were located at 14 positions on the HA molecule, and eight of them were found in multiple revertants. These were located in five to six distinct regions on the three-dimensional structure of the HA molecule. However, the heat stability of HAs in the revertants was recovered differently depending on the sites of the changed amino acids. The kinetics of transport of the HA protein in the revertants were slightly delayed compared to the wild-type both at permissive and nonpermissive temperatures.     

Changes in DNA supertwist as a response of Bacillus subtilis towards different kinds of stress

Abstract The silent parD ( kis/kid ) stability operon of plasmid R1 is normally repressed by the co-ordinated action of the Kis and Kid proteins. In this report it is shown that a mutation in repA , the gene of the plasmid replication protein, that reduces two-fold the copy number of the plasmid, leads to the derepression of the parD system. This derepression can be prevented by a suppressor mutation in copB, a copy number control gene of plasmid R1, that increases the efficiency of replication of the repA mutant. Derepression of the wild-type parD system leads to high plasmid stability. These data show the activation of a plasmid stability operon by a mutation that reduces the efficiency of wild-type plasmid replication.     

Methane monooxygenase mutants of Methylosinus trichosporium constructed by marker-exchange mutagenesis

Abstract Methylosinus trichosporium OB3b synthesizes a soluble cytoplasmic methane monooxygenase when grown in copper-depleted medium and a membrane-bound particulate methane monooxygenase under copper-replete conditions. The genes encoding the hydroxylase component of soluble methane monooxygenase, carried on a plasmid in Escherichia coli , were insertionally inactivated using a kanamycin cassette and transferred back into M. trichosporium by conjugation. Marker-exchange mutagenesis, via a double homologous recombination event, yielded a soluble methane monooxygenase-negative mutant which grew only on methane using the particulate methane monooxygenase during copper-replete growth conditions, thus proving that the two methane oxidation systems in this methanotroph are genetically distinct.     

Inheritance of alleles for Cgy1 and Gy4 storage protein genes in soybean

Summary A cultivar lacking the glycinin subunit A₅A₄B₃ (Raiden) was crossed with one lacking the -subunit of -conglycinin (Keburi). Analysis of F₂ and F₃ progeny indicated that the missing bands of the A₅A₄B₃ and the -subunit were each controlled by a recessive allele of two independently segregating genes. Gene symbols Gy ₄/gy ₄ and Cgy ₁/cgy ₁ were proposed for the genes which confer the presence or absence of the glycinin and conglycinin subunits, respectively.Cooperative research of USDA-ARS and the Indiana Agric. Exp. Stn., Purdue Univ., West Lafayette, IN 47907, USA. Indiana Agric. Exp. Stn. Journal Article 9675. Financial support from the American Soybean Association Research Foundation is gratefully acknowledged     

Procedure for the identification of Escherichia coli mutants affected in components containing glycerol derived from phospholipid turnover: Isolation of mutants lacking glycerol in membrane-derived oligosaccharides (MDO)

Abstract A mutant screening procedure is described which allows the identification of mutants carrying lesions in lipoprotein, membrane-derived oligosac-charides (MDO), and other compounds of the E. coli cell envelope containing glycerol derived from phospholipid metabolism. Two mutants lacking glycerol in MDO and one mutant devoid of lipoprotein demonstrate the usefulness of the procedure.     

Spiral growth in the radially-expanding piloboloid mutants ofPhycomyces blakesleeanus

The growth zone of the sporangiophore of a piloboloid mutant,pil, ofPhycomyces expands radially at an increased rate until the growth zone becomes nearly spherical, in sharp contrast to that of the wild-type sporangiophore which exhibits longitudinal elongation only and is conical. The rotation of thepil sporangiophore reverses its direction from clockwise (CW) to counterclockwise (CCW) during the period of increased radial expansion, and the CCW rotation continues as long as does the radial expansion. The direction of rotation and the time of reversal are correlated with the relative rates of cell-wall expansion in the longitudinal and transverse directions. The CCW rotation of the sporangiophore of this mutant can be explained by the behavior of the microfibrils, as previously proposed to explain the rotation of the wild-type sporangiophore.Abbreviations CW clockwise - CCW counterclockwise — both as viewed from above     

The roles of nitrate and ammonium in the regulation of the development of nitrate reductase in Chlamydomonas reinhardii

The regulation of the development of nitrate reductase (NR) activity in Chlamydomonas reinhardii has been compared in a wild-type strain and in a mutant (nit-A) which possesses a modified nitrate reductase enzyme that is non-functional in vivo. The modified enzyme cannot use NAD(P)H as an electron donor for nitrate reduction and it differs from wild-type enzyme in that NR activity is not inactivated in vitro by incubation with NAD(P)H and small quantities of cyanide; it is inactivated when reduced benzyl viologen or flavin mononucleotide is present. After short periods of nitrogen starvation mutant organisms contain much higher levels of terminal-NR activity than do similarly treated wild-type ones. Despite the inability of the mutant to utilize nitrate, no nitrate or nitrite was found in nitrogen-starved cultures; it is therefore concluded that the appearance of NR activity is not a consequence of nitrification. After prolonged nitrogen starvation (22 h) the NR level in the mutant is low. It increases rapidly if nitrate is then added and this increase in activity does not occur in the presence of ammonium, tungstate or cycloheximide. Disappearance of preformed NR activity is stimulated by addition of tungstate and even more by addition of ammonium. The results are interpreted as evidence for a continuous turnover of NR in cells of the mutant with ammonium both stimulating NR breakdown and stopping NR synthesis. Nitrate protects the enzyme from breakdown. Reversible inactivation of NR activity is thought to play an insignificant rôle in the mutant.Abbreviations NR nitrate reductase - BV benzyl viologen     

Effect of ubiquinone extraction on ubiquinol-1 oxidase activity in beef heart mitochondria

Extraction of endogenous ubiquinone with different methods does not influence ubiquinol oxidase activity in lyophilized mitochondria in terms ofK _M, although a decrease ofV _max is sometimes observed. Experiments with submitochondrial particles from a UQ-deficient mutant ofS. cerevisiae confirm the results with UQ-depleted mitochondria and support the idea that endogenous ubiquinone is not required for the oxidation of exogenous ubiquinols by complex III.