Survival of phage M13 with uracils on one or both DNA strands

Summary The survival of M13 DNA was studied after partial replacement of thymine by uracil in the bacteriophage. Uracils carry the same genetic information as the thymines. Nevertheless in Escherichia coli wild-type cells, uracils in DNA are replaced by thymines by excision repair initiated by uracil-DNA glycosylase (UDG). Thus inactivation of uracil-containing phage DNA is solely due to repair initiated by UDG. Incorporation of uracils was achieved in one or in both strands, either randomly or site-specifically using differently uracylated oligonucleotides. The results show that up to 580 uracils can be repaired without a significant decrease in survival if the uracils are localized in the (–) strand only. Incorporation of 246 uracils into the (+) strand leads to 30% or 10% survival when expressed in Escherichia coli strains CMK and JM103, respectively. However, when uracils are distributed over both strands a sharp decrease in survival occurs. This shows that the repair of two uracils localized in close proximity on opposite strands of the DNA by the excision repair mechanism is difficult, whereas uracils occurring in one strand are repaired more efficiently, irrespective of their number.     

Genetic linkage map of rye (Secale cereale L.)

Communicated by G. Wenzel     

Behavioral responses of female oriental fruit flies to the odor of papayas at three ripeness stages in a laboratory flight tunnel (Diptera: Tephritidae)

Behavioral responses of adult female oriental fruit flies, Dacus dorsalisHendel, to the odor of papayas from three ripeness classes were studied using a threechoice flight tunnel bioassay. Laboratoryreared flies were allowed to respond freely to any of three papaya odors (mature green, colorbreak to one-fourth ripe, and one-half to full ripe) emanating from identical (spherical) fruit models. Five behaviors were measured in assessing the fly's relative attraction to the odors (number of landings), arrestment (total fly seconds on sphere), fly-fly interactions on the fruit model (maximum and modal fly density), and acceptance for oviposition (total eggs laid). Females showed no significant difference in total fly landings based on all age classes combined. Significant differences were noted among age classes. Females spent more total time on the sphere and showed a higher maximum density and modal fly density to ripe fruit than to green fruit odors. Ovipositional acceptance of fruit models based on the total number of eggs laid in a sphere was greater in response to the ripefruit odor than to the other two odor classes. Olfactorystimulated behavioral responses of females to the odor of ripe papayas were significantly different from the other ripeness classes for all behaviors at 8 days postemergence and then declined in 11-day-old flies. Behavioral responses were greater during the afternoon than in the morning. Observations of wild oriental fruit flies to papayas in the field indicated a preference for residing on riper fruit. The results of this study are discussed with regard to the role of olfactory inputs generated by the odor of ripening fruit on female attraction and oviposition behavior resulting in infestation of papayas by oriental fruit fly.     

小偃6号小麦旗叶直立基因的染色体定位

本文首次对小麦旗叶姿态进行了比较系统的细胞遗传学研究。单体、端体的F_1及F_2分析表明:中国春2D染色体上至少有两个旗叶下披基因,即位于2DL上的P_1和2DS上的P_2,前者表达能力很强,后者则较弱,与小偃6号旗叶直立基因共存时分别表现为显性和隐性;小偃6号的旗叶直立基因E也位于2D染色体上,同(P_1+P_2)共存时表现为隐性,仅与P_2共存时则表现为显性。文章还就这些基因的染色体操作等进行了讨论。     

Readiness to lay in the blowfly Lucilia cuprina is unaffected by oviposition site-deprivation or egg-load

Oviposition by Lucilia cuprina Wiedemann (Diptera, Calliphoridae) was examined in relation to period of oviposition site-deprivation and egg-load. Effects of oviposition site-deprivation were examined by comparing oviposition performance of individual females that had matured their batch of oocytes within the previous 24 h with that of females which had reached ovarian maturity 8 days previously. Egg-load was manipulated by causing females of this anautogenous species to consume different amounts of protein-rich material. In no-choice experiments, individual females of the different categories were given access for 4 h to oviposition substrate, soaked with (i) liver exudate, (ii) the exudate diluted 16-fold or (iii) the undilated exudate containing the oviposition deterrent sodium chloride at a concentration of 2 M. These solutions elicited oviposition from different proportions of females, but neither these proportions, nor the interval between introduction of the oviposition site and the initiation of oviposition, was significantly affected by the period of oviposition site-deprivation or the number of eggs matured by the females.

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Résumé L'effet de la privation de lieu de ponte a été étudié en comparant les pontes de femelles isolées ayant formé leurs ufs mûrs dans les 24 heures précédentes, à celles de femelles ayant atteint leur maturité sexuelle 8 jours avant. La rétention ovocytaire est provoquée en faisant consommer aux femelles de cette espèce anautogène différentes quantités d'aliments riches en protéines. La ponte de femelles dont le contingent total de leurs ovocytes s'est développé, — c'est-à-dire 260 —, après consommation ad libitum de foie de mouton pendant 48 heures, a été comparée à celle de femelles ayant formé 190 ovocytes mûrs après ingestion d'une quantité limitée de jus de foie.Dans des expériences sans choix, les femelles isolées de différences catégories ont eu accès pendant 4 heures au substrat de ponte trempé: 1) dans du jus de foie, 2) dans du jus dilué 16 fois, 3) dans du jus de foie non dilué mais contenant NaCl (inhibiteur de la ponte) à la concentration de 2 M. Le jus non dilué a provoqué une forte stimulation, induisant la ponte de 80% des femelles. Le jus dilué et celui contenant NaCl n'ont induit la ponte que de 40% des femelles avec des niveaux de stimulation bien plus faibles. La date d'introduction du lieu de ponte et le taux de rétention des ovocytes mûrs n'ont eu auçun effet sur la proportion de femelles réagissant à ces 3 types de stimulation.

     

Differences between genetic and physical centromere distances in the case of two genes for male sterility in barley

Summary Linkage studies with thirty translocations (one of the two chromosomes involved being number 4) in relation to msg24 (chromosome 4) and thirteen translocations (one of the two chromosomes involved being number 6) in relation to msg6 (chromosome 6) show without exception close linkage for all combinations tested. The results indicate that both genes are located genetically in or close to the centromere regions of their chromosomes.Cytological analysis of two BTT stocks (balanced tertiary trisomics) ascertained the respective chromosome arms (both msg24 and msg6 on the short arms) and revealed marked differences between genetic and physical centromere distances. The reason is obviously the high content of centromeric heterochromatin occupying both the chromosome arms involved.     

Effects of host endocrine gland removal on the permissive status of laboratory rodents to infection by Schistosoma mansoni

Knopf P. M. and Soliman M. 1980. Effects of host endocrine gland removal on the permissive status of laboratory rodents to infection by Schistosoma mansoni. International Journal for Parasitology, 10: 197–204. The capacity of Schistosoma mansoni to complete its life cycle was compared in CD-1 mice (permissive hosts) and Sprague-Dawley rats (nonpermissive hosts) from which the pituitary gland had been removed prior to infection with cercariae. Except for a modest decrease in egg burden, none of the parameters of worm life cycle assessed were affected in hypophysectomized mice. In contrast, all these parameters were affected in hypophysectomized rats, e.g. onset of adult worm elimination was delayed, worm development improved, oviposition increased and miracidia developed. Effects of removal from rats of the thyroid/parathyroid glands on the parasite life cycle were similar to hypophysectomy; adrenalectomy or gonadectomy were without affect. Differences between thyroidectomized and thymectomized rats are discussed. It is concluded that host hormones contribute to the nonpermissive status of rats to Schistosoma mansoni infections.     

Immune expulsion of the nematode Aspiculuris tetraptera from mice given primary and challenge infections.

The distribution of larval Aspiculuris tetraptera was studied in 4-week-old male and female CFLP mice. Whereas on days 10–12 the larvae were entirely confined to the anterior third of the colon, by day 14 larvae could be found throughout the colon. After day 17 the larvae were again restricted to the anterior colon. This change in distribution was co-incident with a loss of a large proportion of the worm burden, which occurred more consistently in female than in male mice.The degree of acquired immunity stimulated by various immunizing regimens was assessed by the survival of a challenge infection in experimental and control mice. It was found that a high level of immunity was achieved by exposure to a 19-day primary infection, a 36-day low-level infection and also by three 6-day infections, in each of which the larvae were removed by piperazine treatment immediately after the crypt phase.     

Chelonus sp. near curvimaculatus venom proteins: Analysis of their potential role and processing during development of host Trichoplusia ni

The venom that Chelonus sp. near curvimaculatus injects into each parasitized Trichoplusia ni egg is entirely injected within the first 8 s of the 19-s oviposition period, before deposition of the parasitoid egg that is injected during the final 1-2 s of the oviposition. The parasitization factor, causing precocious metamorphosis of the host, is injected after the venom, but before the parasite egg. The venom by itself does not cause developmental redirection of the host. Chelonus venom proteins are very stable in the host egg during the first 2 days of egg development. Then, on the last day before hatching, they are rapidly degraded by the proteolytic enzymes appearing in 3-day-old T. ni eggs. Among those that degrade the venom proteins are serine-type proteinases, and at least one seems to be a trypsin-like enzyme.