Extracellular secretion of levansucrase from Zymomonas mobilis in Escherichia coli

Secretion of levansucrase from Zymomonas mobilis in Escherichiacoli by glycine supplement was investigated. A significant amount of levansucrase (about 25% of total activity) was found in intact whole-cells. Cell fractionation experiments showed that levansucrase was found both in the periplasmic space and in the cytoplasmic fraction of E. coli. None or only trace amounts of levansucrase was detected in the extracellular culture broth at 24 h of cultivation and it accrued with the increasing concentration of glycine in the culture medium and duration of the culture period. Optimal glycine concentration for the maximum secretion of levansucrase was in the range of 0.8-1%, in which approximately 20-50% of levansucrase was released into the extracellular fraction at 24 h of cultivation, although glycine retarded the bacterial growth.     

Suppression of PPARγ through MKRN1-mediated ubiquitination and degradation prevents adipocyte differentiation

The central regulator of adipogenesis, PPARγ, is a nuclear receptor that is linked to obesity and metabolic diseases. Here we report that MKRN1 is an E3 ligase of PPARγ that induces its ubiquitination, followed by proteasome-dependent degradation. Furthermore, we identified two lysine sites at 184 and 185 that appear to be targeted for ubiquitination by MKRN1. Stable overexpression of MKRN1 reduced PPARγ protein levels and suppressed adipocyte differentiation in 3T3-L1 and C3H10T1/2 cells. In contrast, MKRN1 depletion stimulated adipocyte differentiation in these cells. Finally, MKRN1 knockout MEFs showed an increased capacity for adipocyte differentiation compared with wild-type MEFs, with a concomitant increase of PPARγ and adipogenic markers. Together, these data indicate that MKRN1 is an elusive PPARγ E3 ligase that targets PPARγ for proteasomal degradation by ubiquitin-dependent pathways, and further depict MKRN1 as a novel target for diseases involving PPARγ.     

Detection of a natural point mutation in Potato virus A that overcomes resistance to vascular movement in Nicandra physaloides., and studies on seed-transmissibility of the mutant virus

Isolate M of Potato virus A (PVA‐M; genus Potyvirus) is avirulent in Nicandra physaloides L. (family Solanaceae). The inoculated leaves are infected but no systemic infection is observed. Forty plants of ‘Black Pod’ (BP) and ‘Black Pod Alba’ (BPA), two variants of N. physaloides described in this study, were inoculated with PVA‐M. Two plants of BP and one plant of BPA were systemically infected. Mosaic, blistering and dark green islands developed on the systemically infected leaves, and flowers showed colour‐break symptoms. PVAprogeny were sequence‐characterised for the 6K2 protein and viral genome‐linked protein (VPg) encoding regions known to control the long distance movement of PVA in N. physaloides. All virus progeny (designated as PVA‐Mm) in the systemically infected leaves of the plants inoculated with PVA‐M contained only a single amino acid substitution (Vail 16Met) in the central part of VPg due to a nucleotide substitution G6033A, as compared to PVA‐M. Other PVA isolates that infected N. physaloides systemically also contained Metll6 in VPg. In a previous study using chimeric viruses, Metl16 in VPg was shown to be a major determinant for vascular movement of PVA in N. physaloides, and this study reveals that the mutation for Metl16 can occur in vivo during replication of the avirulent PVA‐M in infected plants. Immunolocalisation studies on BP and BPA plants showed that the pods (berries) and seed coat contained PVA‐Mm in the developing seeds, but no virus was detected in embryons. Up to 27% of the mature seeds contained PVA‐Mm but no transmission to seedlings was observed in a total of 450 seeds tested, and no test plants were infected following mechanical inoculation with extracts prepared from the seeds.     

Timing of breeding of Tengmalm's Owl Aegolius funereus in relation to vole dynamics in western Finland

Timing of breeding in Tengmalm's Owl was studied in western Finland for 13 years. During 1973-85, half of the females started laying before 4 April, near the seasonal low of main food abundance (voles), and earlier than in southern Finland or as early as in southeastern Norway. The reason for this latitudinal trend is the shallow snow cover of the study area. The annual variation in the median laying dates was one month and was negatively correlated with the spring abundance of Microtus voles. The mean clutch size was related to the start of laying with early clutches being larger than late ones. These findings accord with the 'food limitation hypothesis', which states that laying begins as soon as the female can accumulate enough energy stores for forming eggs. Early breeding is adaptive, since juveniles of early clutches probably survive better during their first winter. In adults, early nesting improves the chances of rearing two broods per year, allows them to moult after breeding and gives more time to accumulate fat reserves to survive the winter. Tengmalm's Owl is one of the earliest breeders among North European birds. This is possible because of its hole-nesting and resident habits, small body-size in relation to the main prey and the greatest sexual size dimorphism among European owls.     

Plasma thyroxine-binding proteins and thyroid hormone levels in primate species; is callithricidae thyroid hormone resistant?

Thyroxine(T4)-binding to serum proteins in primates; catarrhini, prosimiae, and platyrrhini were studied by polyacrylamide gel electrophoresis T4 binding analysis. From the electrophoretic analysis, it was shown that thyroxine-binding proteins similar to human thyroxine-binding globulin (TBG) and thyroxine-binding prealbumin (TBPA) were present in catarrhini and prosimiae species, but not in platyrrhini (callithricidae and cebidae). T4-binding analysis also revealed that catarrhini and prosimiae have a high affinity T4-binding protein similar to human TBG. The association constant (Ka) for T4 of the plasma proteins in these species was approximately 2.0 X 10(10) M-1. On the other hand, it was unable to demonstrate a high affinity binding site for T4 in the plasma of platyrrhini species. Both the total and free thyroid hormone concentrations in catarrhini and prosimiae were similar to those in human. Total T4 in cebidae, one of the platyrrhini species, was extremely low. Among 8 animals examined, T4 in 6 was undetectable by radioimmunoassay and the mean T4 of the other two was 2.8 micrograms/dl. However, free thyroid hormone concentrations were similar to those in human. In callithricidae, another platyrrhini species, T4 in plasma was 6.90 +/- 2.11, which is comparable to the level in normal human subjects. However, in this species, high-affinity T4-binding protein was lacking and free thyroid hormone concentrations were extremely high (most were higher than the assay limit). Although the thyroid function of callithricidae remains to be studied, it will be interesting if callithricidae is resistant to thyroid hormone action.     

Regulation of prolactin gene expression during early pregnancy in rats

We have shown that administration of estrogen which increases prolactin (PRL) synthesis in the rat may be mediated by an increase in poly [adenosine diphosphate ribose (ADP-ribose)] synthesis. Present investigation was attempted to study whether poly (ADP-ribose) synthesis is involved in rat PRL gene expression during early pregnancy. Anterior pituitaries were obtained on days 0, 2, 4, 6, 8, 10 and 12 of pregnancy (group C). Another group of pregnant rats was given nicotinamide, an inhibitor of poly (ADP-ribose) synthesis twice a day intra-peritoneally from day 0 to the day of sacrifice (group N). Serum estradiol (E2) concentration was determined by radioimmunoassay. PRL mRNA was measured by cytoplasmic dot hybridization using 32P-labeled cDNA. Poly (ADP-ribose) synthesis was assessed by incubating purified nuclei with 14C-nicotinamide adenine dinucleotide. The serum concentration of E2 increased between days 2 and 4, and on day 6 it decreased to the level of day 0. It remained low until day 12. No difference in the serum E2 level was observed in groups C and N. In group C, PRL mRNA increased from day 2 and remained high until day 8. In group C, poly (ADP-ribose) synthesis increased between days 2 and 4, decreased on day 6 to the level of day 0, and thereafter gradually increased until day 10. Administration of nicotinamide abolished the increase in poly (ADP-ribose) synthesis observed in group C during early pregnancy. In group N, the increase in PRL mRNA was completely suppressed. It is suggested that the increase in PRL mRNA in early pregnancy may be mediated by increased poly (ADP-ribose) synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Interpopulation differences in pupal size and fecundity are not associated with occurrence of outbreaks in Epirrita autumnata (Lepidoptera, Geometridae)

Abstract.

• 1 Among-population differences in pupal mass were studied in a geometrid, Epirrita autumnata. Some Epirrita autumnata populations regularly reach outbreak densities while others are never known to do so. Because adults do not feed, pupal mass of females correlates strongly with fecundity.
• 2 Larvae were collected from twelve field sites. Ten of our sample populations originated within the outbreak range of the species and represented different phases of outbreaks. Two populations originated outside the outbreak range.
• 3 Pupal mass of field-collected E. autumnata varied significantly among populations. The peak phase populations had the smallest pupae and the biggest were found in low density populations outside the outbreak range.
• 4 Offspring of moths from each population were reared under identical conditions in two larval densities. Significant differences were not found in pupal mass among populations. That is, the inherent size, correlated with fecundity of moths, was not different between populations originating within and outside the outbreak range, nor among collections from different densities or phases of the outbreaks.
• 5 Rearing density did not interact in a consistent way with population.
• 6 As far as size and fecundity are concerned, the results do not support Chitty's hypothesis that differences in genetic composition of the population at low and high density phases generate cyclic fluctuations of population density.
• 7 Because no hereditary or maternal differences were found in size and fecundity between E.autumnata originating within and outside the outbreak range, variation in reproductive capacity cannot explain why outbreaks occur only in some populations.