Developmental and genetic mosaic analysis of Drosophila m-dy mutants: Tissue foci for behavioral and morphogenetic defects

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.     

水稻体细胞无性系R_1、R_2代中的雄性育性变异观察

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。     

Projection pattern of sensory neurons in the central nervous system of a homeotic mutation of the moth Manduca sexta

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.     

A temperature-sensitive mutant ofEscherichia coli with an alteration in ribosomal protein L22

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.     

Invasion of thehobo transposable element studied byin situ hybridization on polytene chromosomes ofDrosophila melanogaster

The invasion kinetics ofhobo transposable element in theDrosophila melanogaster genome was studied byin situ hybridization on the polytene chromosomes. Six independent lines ofDrosophila melanogaster flies that had been previously transformed by microinjection of the pHFL1 plasmid containing a completehobo element were followed over 50 generations. We observed thathobo elements were scattered on each of the chromosome arms, with more insertion sites on the 3R arm. The total number of insertion sites remains quite small, between four and six, at generation 52. On the 2R arm, a short inversion appeared once at generation 52. Most of the integration sites reported here were already described for several transposons but some of them appear to be hotspots forhobo elements.     

A new yeast gene, HTR1, required for growth at high temperature, is needed for recovery from mating pheromone-induced G1 arrest

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).     

Changes in in vivo fluorescence quenching in rye and barley as a function of reduced PSII light harvesting antenna size

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 (q_s) 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 q_s in darkness revealed a fast initial decay, related to relaxation of the high-energy-state dependent (q_E) part of q_s. 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 q_s and q_s were similar in control grown barley chlorina F2 and IML-grown WT rye and barley, but q_s was reduced by 30 to 35% and q_s by 50 to 65%, respectively, as compared to control-grown. WT plants. No significant q_s 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 q_s is detectable even in the absence of LHCII. Only when the proximal antennae are totally absent, does q_E completely disappear. We conclude that the presence of LHCII is not an absolute requirement for q_E-quenching and suggest that distal as well as proximal antenna may contribute to q_E in vivo.     

Hydrotropism and its interaction with gravitropism in roots

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.     

The role of the hexose transporter in the chloroplasts of Arabidopsis thaliana L.

The metabolism of wild-type Arabidopsis thaliana L. and its mutant TC265 were compared in order to reveal the role of the chloroplast glucose transporter. Plants were grown in a 12-h photoperiod. From 20 to 40 days after germination, starch per gram fresh weight of shoot in the mutant was four times that in the wild type. The extent of this difference did not alter during this period. Stereological analysis showed that the chloroplasts in the mutant were larger than those in the wild type; the thylakoids appeared to be distorted by the high starch content. [U-¹⁴C]Glucose and [U-¹⁴C]glycerol were supplied, separately, to excised leaves in the dark. [U-¹⁴C]Glucose was a good precursor of sucrose in the wild type and mutant; [U-¹⁴C]glycerol was a poor precursor of sucrose in both. The distribution of ¹⁴C in the wild type was used to calculate that the net flux was from hexose monophosphates to triose phosphates, not vice versa. During the first 4 h of the night the sugar content (75% sucrose, 20% glucose) of the leaves of the mutant dropped sharply, and at all times during the night it was less than that of the wild-type leaves. This drop in sugar coincided with a decrease in the rate of respiration. The growth rate of the mutant was less than that of the wild type. Addition of sucrose restored the rate of respiration at night and increased the rate of growth. It is argued that a major function of the glucose transporter in Arabidopsis chloroplasts is export of the products of starch breakdown that are destined for sucrose synthesis at night.We thank Professor C.R. Somerville for his generous gift of seed of the Arabidopsis mutant TC265. We are also grateful to Mr B. Chapman for assistance with the preparation of the sections for electron microscopy. R.N.T. thanks the Science and Engineering Research Council for a studentship.