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81.
At the nonpermissive temperature, somatic embryos of the temperature-sensitive (ts) carrot (Daucus carota L.) cell variant ts11 only proceed beyond the globular embryo stage in the presence of medium conditioned by wild-type cells. The causative component in the conditioned medium has been identified as an acidic 32 kD endochitinase. An antiserum raised against the 32 kD chitinase detected this protein in culture medium from ts11 embryo cultures grown at the permissive temperature as well as at the nonpermissive temperature. No difference in biochemical characteristics or in effect on ts11 embryo development could be detected between the 32 kD chitinase purified from wild-type cultures and the chitinase from ts11 cultures grown at the permissive or at the nonpermissive temperature. Compared to the amount present in a ts11 embryo culture at the permissive temperature, a reduction in the amount of 32 kD chitinase was observed during the temperature-sensitive period at the nonpermissive temperature. These results imply that the arrested embryo phenotype of ts11 is not the result of a structural difference in its 32 kD chitinase, but is the result of a transient decrease in the amount of 32 kD chitinase present. Morphological observations indicate that the ts11 phenotype is pleiotropic and also affects the cell wall of nonembryogenic cells. © 1995 Wiley-Liss, Inc.  相似文献   
82.
Mutants of the Drosophila miniature-dusky (m-dy) gene complex display morphogenetic phenotypes (miniature or dusky) caused by a change in the size and/or shape of the epidermal cells comprising the adult wing. In addition to a dusky phenotype, certain Andante-type mutants also exhibit lengthened circadian periods for two different behavioral rhythms. If the latter phenotype results from a direct effect on the circadian pacemaker, the Andante function should be required within the brain. In order to define the tissues that require the morphogenetic and behavioral functions, we have carried out a genetic mosaic analysis. This study demonstrates that normal wing morphogenesis is entirely dependent on the genotype of wing cells. Furthermore, temperature-shift experiments with a temperature-sensitive dy mutant indicate that the morphogenetic function is required during adult development, and after the cessation of wing epidermal cell proliferation. At this time in development, a columnar epithelium in the developing wing becomes flattened into the mature wing blade, and we postulate that the cell-size defect of m-dy mutants results from an alteration of this mor-phogenetic process. In contrast to the wing mor-phogenesis phenotype, the characterization of locomotor activity in mosaic adults revealed a strong correlation between the head genotype and the Andante circadian-period phenotype. This result indicates that neural tissues mediate the rhythm function. Thus, the behavioral and morphogenetic functions require gene expression in distinct tissues. Furthermore, the behavioral results are consistent with a requirement for Andante function within circadian pacemaker neurons. © 1995 Wiley-Liss, Inc.  相似文献   
83.
水稻体细胞无性系R_1、R_2代中的雄性育性变异观察   总被引:11,自引:0,他引:11  
通过水稻幼穗培养,1991-1992两年间,在5个品种(珍汕97B、红源A、包源A、W6154s,和南广占)中共获得了50株雄性不育变异株,其中R_1代有48株,R_2代有2株。在R1代,共获得5268株再生植株,雄性不育变异的平均频率为0.91%(0.83-1.08%);在R_2代(珍汕97B)发生雄性不育变异的频率为2%。本文报道了多种花粉败育类型之间可以相互转变现象,此外不育和可育之间亦可以相互转变。对离体培养产生的雄性不育变异株用一批现有CMS(Cytoplasmicmalesterile)不育系的典型保持系、恢复系进行测交,结果表明,W6154s产生的雄性育性变异株仍保持核不育的特性;红源A产生的雄性育性变异株有的可能是嵌合体,有的其败育花粉类型虽发生了变化,但其恢保关系并没有改变,有的则可能已转成类似WA型的不育材料;南广占产生的典败变异株,其恢保关系类似WA型,可能属核不育转成CMS的首例发现。  相似文献   
84.
Octopod (Octo) is a mutation of the moth Manduca sexta, which transforms the first abdominal segment (A1) in the anterior direction. Mutant animals are characterized by the appearance of homeotic thoracic-like legs on A1. We exploited this mutation to determine what rules might be used in specifying the fates of sensory neurons located on the body surface of larval Manduca. Mechanical stimulation of homeotic leg sensilla did not cause reflexive movements of the homeotic legs, but elicited responses similar to those observed following stimulation of ventral A1 body wall hairs. Intracellular recordings demonstrated that several of the motoneurons in the A1 ganglion received inputs from the homeotic sensory hairs. The responses of these motoneurons to stimulation of homeotic sensilla resembled their responses to stimulation of ventral body wall sensilla. Cobalt fills revealed that the mutation transformed the segmental projection pattern of only the sensory neurons located on the ventral surface of A1, resulting in a greater number with intersegmental projection patterns typical of sensory neurons found on the thoracic body wall. Many of the sensory neurons on the homeotic legs had intersegmental projection patterns typical of abdominal sensory neurons: an anteriorly directed projection terminating in the third thoracic ganglion (T3). Once this projection reached T3, however, it mimicked the projections of the thoracic leg sensory neurons. These results demonstrate that the same rules are not used in the establishment of the intersegmental and leg-specific projection patterns. Segmental identity influences the intersegmental projection pattern of the sensory neurons of Manduca, whereas the leg-specific projections are consistent with a role for positional information in determining their pattern. © 1995 John Wiley & Sons, Inc.  相似文献   
85.
To study the physiological role of the creatine kinase/phosphocreatine (CK/PCr) system in cells and tissues with a high and fluctuating energy demand we have concentrated on the site-directed inactivation of the B- and M-CK genes encoding the cytosolic CK protein subunits. In our approach we used homologous recombination in mouse embryonic stem (ES) cells from strain 129/Sv. Using targeting constructs based on strain 129/Sv isogenic DNA we managed to ablate the essential exons of the B-CK and M-CK genes at reasonably high frequencies. ES clones with fully disrupted B-CK and two types of M-CK gene mutations, a null (M-CK) and leaky (M-CK1) mutation, were used to generate chimaeric mutant mice via injection in strain C57BL/6 derived blastocysts. Chimaeras with the B-CK null mutation have no overt abnormalities but failed to transmit the mutation to their offspring. For the M-CK and M-CK1 mutations successful transmission was achieved and heterozygous and homozygous mutant mice were bred. Animals deficient in MM-CK are phenotypically normal but lack muscular burst activity. Fluxes through the CK reaction in skeletal muscle are highly impaired and fast fibres show adaptation in cellular architecture and storage of glycogen. Mice homozygous for the leaky M-CK allele, which have 3-fold reduced MM-CK activity, show normal fast fibres but CK fluxes and burst activity are still not restored to wildtype levels.  相似文献   
86.
A temperature-sensitive, protein synthesis-defective mutant ofEscherichia coli exhibiting an altered ribosomal protein L22 has been investigated. The temperature-sensitive mutation was mapped to therplV gene for protein L22. The genes from the wild type and mutant strains were amplified by the polymerase chain reaction and the products were sequenced. A cytosine to thymine transition at position 22 of the coding sequence was found in the mutant DNA, predicting an arginine to cysteine alteration in the protein. A single cysteine residue was found in the isolated mutant protein. This amino acid change accounts for the altered mobility of the mutant protein in two-dimensional gels and during reversed-phase HPLC. The temperature-sensitive phenotype was fully complemented by a plasmid carrying the wild type L22 gene. Ribosomes from the complemented cells showed only wild type protein L22 by two dimensional gel analysis and were as heat-resistant as control ribosomes in a translation assay. The point mutation in the L22 gene is uniquely responsible for the temperature-sensitivity of this strain.  相似文献   
87.
Gibberellins: perception,transduction and responses   总被引:40,自引:0,他引:40  
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88.
A new temperature-sensitive mutant of Saccharomyces cerevisiae was isolated. Arrested cells grown at the nonpermissive temperature were of dumb-bell shape and contained large vacuoles. A DNA fragment was cloned based on its ability to complement this temperature sensitivity. The HTR1 gene encodes a putative protein of 93 kDa without significant homology to any known proteins. The gene was mapped between ade5 and lys5 on the left arm of chromosome VII. The phenotype of the gene disruptant appeared to be strain-specific; disruption of the gene in strain W303 caused the cells to become temperature sensitive. The arrested phenotype here was similar to that of the original is mutant and cells in G2/M phase predominated at high temperature. Another disruptant in a strain YPH background grew slowly at high temperature due to slow progression through G2/M phase, and morphologically abnormal (elongated) cells accumulated. A single-copy suppressor that alleviated the temperature-sensitive defects in both strains was identified as MCS1/SSD1. The wild-type strains W303 and YPH are known to carry defective MCS1/SSD1 alleles; hence HTR1 may function redundantly with MCS1/SSD1 to suppress the temperature-sensitive phenotypes. In addition, based on a halo bioassay, the disruptant strains appeared to be defective in recovery from, or adaptive response to G1 arrest mediated by mating pheromone, even at the permissive temperature. Thus the gene has at least two functions and is designated HTR1 (required for high temperature growth and recovery from G1 arrest induced by mating pheromone).  相似文献   
89.
The relationship between the size of the light harvesting antenna to photosystem II (LHCII) and quenching of non-photochemical and dark level fluorescence was studied in wild-type rye (Secale cereale L. cv. Musketeer) and barley (Hordeum vulgare L. cv. Gunilla) as well as in the barley chlorophyll b-less chlorina F2 mutant (H. vulgare L. cv. Dornaria, chlorina-F2). Exposure for 10 min to an irradiance of 500 μmol m?2 s?1 resulted in a strong (0.71–0.73) non-photochemical (qs) quenching of the fluorescence yield in wild-type (WT) material, while the barley chlorina F2-mutant was quenched to 75% of this level. Relaxation of qs in darkness revealed a fast initial decay, related to relaxation of the high-energy-state dependent (qE) part of qs. Etiolated seedlings of rye and barley exposed to intermittent light (IML) for 36 cycles of 2 min light and 118 min darkness had suppressed Chl b and LHCII-production in both WT rye and barley, while the barley chlorina F2-mutant became totally devoid of all LHCII-polypeptides. It was found that the levels of qs and qs were similar in control grown barley chlorina F2 and IML-grown WT rye and barley, but qs was reduced by 30 to 35% and qs by 50 to 65%, respectively, as compared to control-grown. WT plants. No significant qs could be detected in IML-grown barley chlorina F2. It is clear, from these changes in in vivo fluorescence quenching in rye and barley that a significant level of qs is detectable even in the absence of LHCII. Only when the proximal antennae are totally absent, does qE completely disappear. We conclude that the presence of LHCII is not an absolute requirement for qE-quenching and suggest that distal as well as proximal antenna may contribute to qE in vivo.  相似文献   
90.
We have studied hydrotropism and its interaction with gravitropism in agravitropic roots of a pea mutant and normal roots of peas (Pisum sativum L.) and maize (Zea mays L.). The interaction between hydrotropism and gravitropism in normal roots of peas or maize were also examined by nullifying the gravitropic response on a clinostat and by changing the stimulus-angle for gravistimulation. Depending on the intensity of both hydrostimulation and gravistimulation, hydrotropism and gravitropism of seedling roots strongly interact with one another. When the gravitropic response was reduced, either genetically or physiologically, the hydrotropic response of roots became more unequivocal. Also, roots more sensitive to gravity appear to require a greater moisture gradient for the induction of hydrotropism. Positive hydrotropism of roots occurred due to a differential growth in the elongation zone; the elongation was much more inhibited on the moistened side than on the dry side of the roots. It was suggested that the site of sensory perception for hydrotropism resides in the root cap, as does the sensory site for gravitropism. Furthermore, an auxin inhibitor, 2,3,5-triiodobenzoic acid (TIBA), and a calcium chelator, ethyleneglycol-bis-(-aminoethylether)-N,N,N,N- tetraacetic acid (EGTA), inhibited both hydrotropism and gravitropism in roots. These results suggest that the two tropisms share a common mechanism in the signal transduction step.  相似文献   
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