Tissue- and Stage-Specific Expression of Sericin Genes in the Middle Silk Gland of Bombyx mori

Sericin gene expression in the middle silk glands during Bombyx mori larval development was analyzed using probes from a genomic DNA clone for 10.5 kb sericin mRNA. The 10.5 kb mRNA, the most abundant in the fifth instar, is not detected in the third feeding, fourth feeding and fourth moulting stages. It becomes detectable at 2 days of the fifth instar, and accumulates rapidly. The second major mRNA in the late fifth instar, a 9.0 kb component having a similar sequence to the 10.5 kb mRNA, becomes detectable only at 6 and 7 days of the instar by use of the repetitious coding sequence probe of the sericin clone. Using the same probe about 20 kb RNAs with a fainter intensity than that of the major mRNAs are detected. They are present extremely faintly in the third and fourth feeding stages, disappear in the fourth moulting stage, and increase in the fifth instar. Two other faint poly(A)⁺ RNA components are detected by a DNA probe containing the 5' end sequence of the sericin clone. One is 4.3 kb, and appears in the third, fourth and fifth feeding stages but not in the fourth moulting stage. The other is 3.0 kb, and it becomes detectable after 1 day of the fifth instar.     

Effects of ablation of the pars intercerebralis on ecdysteroid quantities and yolk protein expression in the blowfly Protophormia terraenovae

Quantities of ecdysteroid are compared in the haemolymph and ovaries of the blowfly Protophormia terraenovae Robineau‐Desvoidy (Diptera: Calliphoridae) under reproductive (LD 18 : 6 h at 25 °C) and diapause (LD 12 : 12 h at 20 °C) conditions. The effects of ablation of the pars intercerebralis or ovaries on ecdysteroid quantities and of ablation of the pars intercerebralis on yolk protein expression are examined. Under reproductive conditions, the levels of ecdysteroid in vitellogenic females are high, although the levels in previtellogenic females and females with mature ovaries are low. Under diapause conditions, there are low quantities of ecdysteroid in both the haemolymph and ovaries. Ecdysteroid titres in the haemolymph are not significantly affected by the removal of the ovaries, suggesting that tissues other than the ovaries are also involved in the production of ecdysteroids. Reproductive females in which the pars intercerebralis of the brain is experimentally ablated have ecdysteroid levels that are not significantly different from sham‐operated or intact females. However, yolk protein expression in the fat body is suppressed after removal of the pars intercerebralis. These results suggest that the suppression of ecdysteroid levels in the haemolymph and ovaries is associated with reproductive diapause, and that the pars intercerebralis could play a role in yolk protein synthesis without mediating ecdysteroid production.     

Isolation of tobacco mesophyll cells in intact and active state

A procedure using a fungal pectinase was developed to rapidlyrelease mesophyll cells from tobacco leaves. Fifty to ninetyper cent of the released cells were morphologically intact andwere converted into spherical protoplasts by cellulase treatment.Cells isolated from tobacco mosaic virus-inoculated leaves supportedmultiplication of the virus during subsequent incubation. (Received December 14, 1967; )     

Occurrence of 2-Aminobutanoic Acid in the Incubation Medium of Mixed Rumen Ciliate Protozoa1

An unknown, ninhydrin-positive substance detected on paper chromatograms of the endogenous metabolites of mixed rumen ciliate protozoa was isolated and purified by column chromatography with ‘Dowex’ 50-X8 resin and identified as 2-aminobutanoic acid (α-amino-n-butyric acid) on the basis of elementary analysis, mass spectrometry, paper chromatography, infrared spectrometry, and melting point.     

Nuclear Receptors in Mosquito Vitellogenesis

Vitellogenesis in insects involves the coordinated activityof the fat body, which produces large amounts of yolk proteinprecursors (YP), and oocytes, which specifically accumulatethese proteins. The expression of YP genes is achieved throughstrict sex-, tissue-, and hormone-specific control in the femalefat body. In mosquitoes, expression of YP genes is controlledby 20-hydroxyecdysone (20E). To elucidate the role of 20E inmosquito vitellogenesis, we cloned cDNAs encoding the Aedesaegypti ecdysteroid receptor (AaEcR) and two isoforms of itsheterodimeric partner, the Ultraspiracle homologue (AaUSP).The two AaUSP isoforms differ in their A/B domains and havedistinct expression patterns. The ecdysone regulation of YPgenes likely involves products of early genes. We cloned thegene of the mosquito homologue to the Drosophila early geneE75 (AaE75) belonging to the nuclear receptor superfamily. Kineticsof AaE75 expression correlate with the expression of YP genes,suggesting that AaE75 may have a regulatory role in YP geneexpression. A second nuclear receptor superfamily member, theNGFI-B homologue AaHR38 is implicated in repression of the ecdysone-signalingpathway in the fat body of the previtellogenic female mosquitoat the state-of-arrest. Finally, three isoforms of the hepatocytenuclear factor 4 (HNF-4) homologue AaHNF-4 are differentiallyexpressed in the mosquito fat body during vitellogenesis, suggestingtheir involvement in regulating vitellogenic events in thistissue.     

Heritability of male mandible length in the stag beetle Cyclommatus metallifer

Numerous coleopteran species express male‐specific “weapon traits” that often show size variations among males, even within a single population. Many empirical studies have demonstrated that environmental conditions during development affect absolute weapon size. However, relatively few studies in horned beetles support the hypothesis that the relationship between weapon size and body size, also referred to as a “scaling relationship” or “static allometry”, is largely determined by genetic factors. In this study, the heritability of absolute mandible length and static allometry between mandible length and body size were estimated in the stag beetle Cyclommatus metallifer. While no significant heritable variation was observed in absolute mandible length, high heritability (h² = 0.57 ± 0.25) was detected in the static allometry between mandible length and body size. This is the first report on the genetic effect on male mandible size in Lucanidae, suggesting that absolute mandible size is largely determined by environmental conditions while the static allometry between weapon size and body size is primarily determined by genetic factors.     

Differences in cellulose digestive systems among castes in two termite lineages

Abstract.  Termites (Isoptera) are eusocial insects and express polyphenism. Soldiers have specialized morphology for colony defense, but their feeding activity is dependent on other colony members. To determine differences in cellulose degradation between soldier and worker termites, enzymatic activity and cellulase gene expression, as well digestive tract histology, are examined in two phylogenetically distant species. In Hodotermopsis sjostesti (family Termopsidae) , endo-β-1,4-glucanase activity is identified in the salivary glands, whereas β-glucosidase activity is identified in salivary glands and hindgut. The relative expression levels of endo-β-1,4-glucanase genes in soldiers are significantly lower than in workers. Thin sections of salivary gland of workers and soldiers are different in H. sjostedti . In Nasutitermes takasagoensis (family Termitidae), the endo-β-1,4-glucanase activity is restricted to the midgut in four tested castes (i.e. three types of workers and soldier). Examination of activity per termite reveals the highest activity in minor workers and the lowest activity in major workers and soldiers. The β-glucosidase activity is also concentrated on the midgut in all four castes. The relative expression level of the endo-β-1,4-glucanase gene does not correspond with its activity in the midgut. In thin sections prepared from N. takasagoensis , the folds and pulvillus in the gizzards, and cuticle structure of soldiers are less developed compared with the other three worker castes. The differences in digestive system among termite castes in terms of caste development in each species are discussed.     

Peroxidase isozymes and their indoleacetate oxidase activity in the Japanese morning glory, Pharbitis nil

Distributions of peroxidase isozymes in various organs of theJapanese morning glory (Pharbitis nil CHOISY) are described.Most peroxidase isozymes had indoleacetate oxidase activity. (Received December 29, 1969; )     

SYNCHRONIZATION OF BUDDING CYCLE IN YEAST CELLS, AND EFFECT OF CARBON MONOXIDE AND NITROGEN-DEFICIENCY ON THE SYNCHRONY

1. A procedure was devised to synchronize the budding cycleof baker's yeast. The method consists of preliminary selectionof the cells by differential centrifugation, combined with treatmentat 40° for 1 hr. On further incubation of the pre-treatedcells in the fresh medium at 27°, a synchronized buddingof the whole population occurs. followed by equally well synchronizedmaturation and separation of the buds formed. 2. The effect of CO on the budding cycle was investigated byintroducing the gas at various stages of the cycle. The mostmarked effect was observed when it was introduced in the inductionperiod of the cycle, resulting in a prolongation of the inductionperiod. Anaerobiosis was found to cause inhibition similar tothat caused by CO described above. 3. 2, 4-Dinitrophenol, when added at the beginning of the inductionperiod, at a low concentration (1.8x 10^–4M), was foundnot to abolish the first budding, but to prolong bud-maturationmarkedly. At higher concentrations of the poison, the firstbudding was markedly retarded, followed by the suppression ofbud-maturation. The budding was completely suppressed at l.8x10^–3M of the poison. 4. The absence of N-source in the incubation medium did notsignificantly affect the first budding, but completely abolishedthe capacity of the cells (both mothers and daughters) for thesecond budding. The lost capacity could be recovered by supplementingthe deficient medium with an N-source (urea), but when the timingof the supply was delayed, the recovery became less and lesssatisfactory. The presence of CO in the gas atmosphere was foundto enhance the deleterious effect of N-deficiency. (Received September 2, 1961; )