Kiyohito Yoshida

Polytene Chromosomal Maps of 11 Drosophila Species: The Order of Genomic Scaffolds Inferred From Genetic and Physical Maps

The sequencing of the 12 genomes of members of the genus Drosophila was taken as an opportunity to reevaluate the genetic and physical maps for 11 of the species, in part to aid in the mapping of assembled scaffolds. Here, we present an overview of the importance of cytogenetic maps to Drosophila biology and to the concepts of chromosomal evolution. Physical and genetic markers were used to anchor the genome assembly scaffolds to the polytene chromosomal maps for each species. In addition, a computational approach was used to anchor smaller scaffolds on the basis of the analysis of syntenic blocks. We present the chromosomal map data from each of the 11 sequenced non-Drosophila melanogaster species as a series of sections. Each section reviews the history of the polytene chromosome maps for each species, presents the new polytene chromosome maps, and anchors the genomic scaffolds to the cytological maps using genetic and physical markers. The mapping data agree with Mullers idea that the majority of Drosophila genes are syntenic. Despite the conservation of genes within homologous chromosome arms across species, the karyotypes of these species have changed through the fusion of chromosomal arms followed by subsequent rearrangement events.

Accumulation of Hsp70 mRNA under environmental stresses in diapausing and nondiapausing adults of Drosophila triauraria

Drosophila triauraria entered reproductive diapause in response to short daylengths and acquired tolerance to heat, cold and desiccation. In this species, the heat-shock response (accumulation of Hsp70 mRNA in response to heat) occurred at 27-41 degrees C, and the level of Hsp70 mRNA did not differ between diapausing and nondiapausing individuals. Hsp70 mRNA was also induced by exposure to -4 or -8 degrees C. However, it was scarcely detected just after the exposure to cold, but accumulated when flies were maintained at normal temperature following the exposure to cold. The level of Hsp70 mRNA was lower in diapausing individuals than in nondiapausing ones when exposed to -4 degrees C, but was not different between them when exposed to -8 degrees C. This species did not synthesize Hsp70 mRNA under desiccation stress irrespective of the diapause state. These results suggest that diapausing individuals of this species acquired tolerance to heat, cold and desiccation independent of the transcriptional regulation of the hsp70 gene

Bacterial Long-Chain Polyunsaturated Fatty Acids: Their Biosynthetic Genes, Functions, and Practical Use

The nutritional and pharmaceutical values of long-chain polyunsaturated fatty acids (LC-PUFAs) such as arachidonic, eicosapentaenoic and docosahexaenoic acids have been well recognized. These LC-PUFAs are physiologically important compounds in bacteria and eukaryotes. Although little is known about the biosynthetic mechanisms and functions of LC-PUFAs in bacteria compared to those in higher organisms, a combination of genetic, bioinformatic, and molecular biological approaches to LC-PUFA-producing bacteria and some eukaryotes have revealed the notably diverse organization of the pfa genes encoding a polyunsaturated fatty acid synthase complex (PUFA synthase), the LC-PUFA biosynthetic processes, and tertiary structures of the domains of this enzyme. In bacteria, LC-PUFAs appear to take part in specific functions facilitating individual membrane proteins rather than in the adjustment of the physical fluidity of the whole cell membrane. Very long chain polyunsaturated hydrocarbons (LC-HCs) such as hentriacontanonaene are considered to be closely related to LC-PUFAs in their biosynthesis and function. The possible role of LC-HCs in strictly anaerobic bacteria under aerobic and anaerobic environments and the evolutionary relationships of anaerobic and aerobic bacteria carrying pfa-like genes are also discussed.

An eye imaginal disc-specific transcriptional enhancer in the long terminal repeat of thetom retrotransposon is responsible for eye morphology mutations ofDrosophila ananassae

Optic morphology (Om) mutations ofDrosophila ananassae are semidominant, neomorphic and nonpleiotropic, map to at least 22 loci scattered throughout the genome, and are associated with the insertion of thetom retrotransposon. Molecular and genetic analyses have revealed that eye morphology defects ofOm mutants are caused by the ectopic or excessive expression ofOm genes in the eye imaginal discs of third instar larvae. It is therefore assumed that thetom element carries tissue-specific gene regulatory sequences which enhance expression of theOm genes. In the present study, we examined whether or not the long terminal repeats (LTR) of thetom element contain such an eye imaginal disc-specific enhancer, usingD. melanogaster transformants containing alacZ gene ligated to thetom LTR. Analyses oflacZ gene expression in the eye imaginal discs of third instar larvae of 18 independently established transformant lines showed that thetom LTR was capable of enhancinglacZ expression in all the transformant lines, but the degree of enhancement varied between lines. In addition, the effect of thetom LTRlacZ gene evidently changed when thetom LTR construct was relocated to different chromosomal positions. On the basis of these findings, it is hypothesized that ectopic and excessive expression of theOm genes in the eye imaginal discs is induced by an eye imaginal disc-specific enhancer present in thetom LTR, the effect of which may be subject to chromosomal position effects.

Four tandem defective P elements associated with positive regulation of theDrosophila melanogaster glucose-6-phosphate dehydrogenase gene

Three high-glucose-6-phosphate dehydrogenase (G6PD)-activity mutants (2512H, S44H, and 1FH) are characterized by two insertion sequences associated with the G6PD locus; one (Ins1; 3.5 kb long in 2512H and S44H and 2.9 kb long in 1FH) is present just 5′ to exon I and consists of a KP′ (the 32nd base of the KP was replaced by guanine), a core sequence and a KP, and the other is 4.2 kb long and resides within an intron. Southern blot analyses of revertants showing low G6PD activity suggested that the insertion sequence responsible for high G6PD activity may be the core sequence but not the flanking KP and KP′ or the Ins2. DNA sequencing data of the clone carrying the core sequence of 2512H demonstrated that the core sequence is another type of defective P elements (core P). Interestingly, a protein(s) was found in the nuclear extract of Canton S embryos that specifically binds to the core P but not to the KP or various fragments of pπ 25.1. In addition, the mutant G6PD activity was found to be affected not only by the genotype, but also by cytoplasmic factors.

Occurrence of trans monounsaturated and polyunsaturated fatty acids in Colwellia psychrerythraea strain 34H

Colwellia psychrerythraea strain 34H is an obligately psychrophilic bacterium that has been used as a model cold‐adapted microorganism because of its psychrophilic growth profile, significant production of cold‐active enzymes, and cryoprotectant extracellular polysaccharide substances. However, its fatty acid components, particularly trans unsaturated fatty acids and long‐chain polyunsaturated fatty acids (LC‐PUFAs), have not been fully investigated. In this study, we biochemically identified Δ9‐trans hexadecenoic acid [16:1(9t)] and LC‐PUFAs such as docosahexaenoic acid. These results are comparable with the fact that the strain 34H genome sequence includes pfa and cti genes that are responsible for the biosynthesis of LC‐PUFAs and trans unsaturated fatty acids, respectively. Strain 34H cells grown under static conditions at 5 °C had higher levels of 16:1(9t) than those grown under shaken conditions, and this change was accompanied by an antiparallel decrease in the levels of Δ9‐cis hexadecenoic acid [16:1(9c)], suggesting that the cis‐to‐trans isomerization reaction of 16:1(9c) is activated under static (microanaerobic) culture conditions, that is, the enzyme could be activated by the decreased dissolved oxygen concentration of cultures. On the other hand, the levels of LC‐PUFAs were too low (less than 3% of the total), even for cells grown at 5 °C, to evaluate their cold‐adaptive function in this bacterium.

Retrotransposon-induced ectopic expression of the Om(2D) gene causes the eye-specific Om(M) phenotype in Drosophila ananassae

Optic morphology (Om) mutations in Drosophila ananassae map to at least 22 loci, which are scattered throughout the genome. Om mutations are all semidominant, neomorphic, nonpleiotropic, and associated with the insertion of a retrotransposon, tom. We have found that the Om(2D) gene encodes a novel protein containing histidine/proline repeats, and is ubiquitously expressed during embryogenesis. The Om(2D) RNA is not detected in wild-type eye imaginal discs, but is abundantly found in the center of the eye discs of Om(2D) mutants, where excessive cell death occurs. D. melanogaster flies transformed with the Om(2D) cDNA under control of the hsp70 promoter display abnormal eye morphology when heat-shocked at the third larval instar stage. These results suggest that the Om(2D) gene is not normally expressed in the eye imaginal discs, but its ectopic expression, induced by the tom element, in the eye disc of third instar larvae results in defects in adult eye morphology.

Structural Confirmation of a Unique Carotenoid Lactoside, P457, in Symbiodinium sp. Strain nbrc 104787 Isolated from a Sea Anemone and its Distribution in Dinoflagellates and Various Marine Organisms

The molecular structure of the carotenoid lactoside P457, (3S,5R,6R,3′S,5′R,6′S)‐13′‐cis‐5,6‐epoxy‐3′,5′‐dihydroxy‐3‐(β‐d‐galactosyl‐(1→4)‐β‐d‐glucosyl)oxy‐6′,7′‐didehydro‐5,6,7,8,5′,6′‐hexahydro‐β,β‐caroten‐20‐al, was confirmed by spectroscopic methods using Symbiodinium sp. strain NBRC 104787 cells isolated from a sea anemone. Among various algae, cyanobacteria, land plants, and marine invertebrates, the distribution of this unique diglycosyl carotenoid was restricted to free‐living peridinin‐containing dinoflagellates and marine invertebrates that harbor peridinin‐containing zooxanthellae. Neoxanthin appeared to be a common precursor for biosynthesis of peridinin and P457, although neoxanthin was not found in peridinin‐containing dinoflagellates. Fucoxanthin‐containing dinoflagellates did not possess peridinin or P457; green dinoflagellates, which contain chlorophyll a and b, did not contain peridinin, fucoxanthin, or P457; and no unicellular algae containing both peridinin and P457, other than peridinin‐containing dinoflagellates, have been observed. Therefore, the biosynthetic pathways for peridinin and P457 may have been coestablished during the evolution of dinoflagellates after the host heterotrophic eukaryotic microorganism formed a symbiotic association with red alga that does not contain peridinin or P457.

Effects of Aerobic Growth on the Fatty Acid and Hydrocarbon Compositions of Geobacter bemidjiensis Bem T

Geobacter spp., regarded as strict anaerobes, have been reported to grow under aerobic conditions. To elucidate the role of fatty acids in aerobiosis of Geobacter spp., we studied the effect of aerobiosis on fatty acid composition and turnover in G. bemidjiensis BemT. G. bemidjiensis BemT was grown under the following different culture conditions: anaerobic culture for 4 days (type 1) and type 1 culture followed by 2-day anaerobic (type 2) or aerobic culture (anaerobic-to-aerobic shift; type 3). The mean cell weight of the type 3 culture was approximately 2.5-fold greater than that of type 1 and 2 cultures. The fatty acid methyl ester and hydrocarbon fraction contained hexadecanoic (16:0), 9-cis-hexadecenoic [16:1(9c)], tetradecanoic (14:0), tetradecenoic [14:1(7c)] acids, hentriacontanonaene, and hopanoids, but not long-chain polyunsaturated fatty acids. The type 3 culture contained higher levels of 14:0 and 14:1(7c) and lower levels of 16:0 and 16:1(9c) compared with type 1 and 2 cultures. The weight ratio of extracted lipid per dry cell was lower in the type 3 culture than in the type 1 and 2 cultures. We concluded that anaerobically-grown G. bemidjiensis BemT followed by aerobiosis were enhanced in growth, fatty acid turnover, and de novo fatty acid synthesis.