Light-stimulated Absorption of Nitrate by Wolffia arrhiza

The mechanism of the light-stimulated absorption of nitrate by Wolffia arrhiza was studied. The nitrate-absorption mechanism in ammonium-grown plants is stimulated by the presence of nitrate. In a manner similar to the absorption of many other ions, the absorption of nitrate follows a typical biphasic pattern in relation to external nitrate concentration. Mechanism 1 is effective at nitrate concentrations up to 0.5 to 0.75 mM and mechanism 2 becomes operative at higher nitrate levels. Light stimulates the absorption of nitrate independently of the effect of light on the reduction of nitrate. The effects of uncouplers, inhibitors, and light of wavelengths of 700 nm or longer indicate that nitrate absorption by Wolffia cells is reduced when non-cyclic electron transport is blocked. It is postulated that under this condition, ATP in the chloroplast (produced by cyclic photophosphorylation) may be less readily transported across the chloroplast envelope than when non-cyclic electron transport is proceeding.     

Pathways of Uptake and Accumulation of Sugars in Tomato Fruit

The route of sucrose unloading from the conducting tissue, theregulation of sucrose hydrolysis and the uptake and subsequentmetabolism of sugars were investigated in the rapidly growingtomato fruit. During the first two weeks of fruit enlargement, the vacuoleaccounted for more than 85% of the protoplast volume and theintercellular space accounted for 20% of the fruit placentaltissue. The plasmodesmatal frequency was highest between phloemparenchyma cells and lowest between phloem sieve cells and phloemparenchyma. The total invertase activity was about 8 µmolglucose g^–1 d. wt min^–1 during the rapid growingperiod and increased six-fold at ripening. The wall-bound invertaseaccounted for less than 11% of the total activity. Invertaseactivity increased with increasing sucrose concentrations (upto 50 mM) in the incubation medium, but decreased at higherconcentrations. Sucrose synthase activity could only be detectedwhen fruit was older than 19 d. The uptake and metabolism of sugars by fruit cells were investigatedby incubation of fruit slices with ¹⁴C-sugars for 3 h. The uptakeof sucrose increased with the sucrose concentration up to 200mM. The rate of glucose uptake and its conversion to the ethanol-insolublefraction were higher than those of sucrose. The uptake of sucrosedid not compete with that of glucose or vice versa, providedthe osmotic potential of the incubation solution was maintainedconstant. The uptake of sucrose was not inhibited by metabolicinhibitors such as PCMBS, CCCP, sodium azide or vanadate. TheATPase activity in the fruit tissue was low. These findings did not identify conclusively the mode of sucroseunloading. However, the uptake of sugars by fruit cells is non-specificand does not appear to require a membrane carrier or plasmalemmaATPase to provide energy for sucrose uptake. Fruit, invertase, Lycopersicon esculentum, phloem unloading, plasmodesmata, sucrose     

News from the Biological Stain Commission No. 5

In this fifth issue of News from the Biological Stain Commission (BSC), under the heading of Regulatory Affairs, the BSC's International Affairs Committee provides more information from the meeting of the International Standards Organization ISO/TC 212 Committee that took place on June 2–4, 2008 at Vancouver, Canada. In addition, we give an update on the current situation regarding the supplies of hematoxylin.     

Conservation of Hipparchia autonoe (Esper) (Lepidoptera: Nymphalidae), Natural Monument in South Korea

Hipparchia autonoe, designated Natural Monument no. 458, is a species inhabiting Mt. Halla on Jeju Island, which is the only habitat of H. autonoe in South Korea. Recently, this species is in danger of extinction as the population has been remarkably reduced because its host plants and nectar plants are gradually disappearing due to plant succession in its habitat. On the climbing road of Jeju Island Eorimok, H. autonoe used to be observed at and above 1300 m a.s.l. However, since Sasa quelpaertensis has recently expanded its habitat up to 1400 m, H. autonoe is now observed at and above 1500 m. In Mongolia, the population of H. autonoe seems quite stable as there are dense populations of a host plant and nectar plants. Accordingly it is judged that we can maintain a stable community for support of H. autonoe if we successfully manage the host plant and nectar plant communities by controlling the density of S. quelpaertensis using biological and physical control methods. Comparative analysis of DNA barcode region of COI (658 bp) was done to check the homogeneity and the genetic diversity of H. autonoe collected in Korea and Mongolia. The DNA sequence difference among individuals collected in South Korea was 0.0–0.2%, and in Mongolia 0.0–1.4%. This confirmed a 0.06–1.2% barcoding gap. We believe that this result will provide basic information useful to guide conservation of H. autonoe in South Korea.     

MicroRNA expression profiling in neurogenesis of adipose tissue-derived stem cells

Adipose tissue-derived stem cells (ADSCs) are one population of adult stem cells that can self renew and differentiate into multiple lineages. Because of advantages in method and quantity of acquisition, ADSCs are gaining attention as an alternative source of bone marrow mesenchymal stem cells. In this study, we performed microRNA profiling of undifferentiated and of neurally-differentiated ADSCs to identify the responsible microRNAs in neurogenesis using this type of stem cell. MicroRNAs from four different donors were analysed by microarray. Compared to the undifferentiation control, we identified 39–101 microRNAs with more than two-fold higher expression and 3–9 microRNAs with two-fold lower expression. The identified microRNAs were further analysed in terms of gene ontology (GO) in relation with neurogenesis, based on their target mRNAs predicted by computational analysis. This study revealed the specific microRNAs involved in neurogenesis via microRNA microarray, and may provide the basic information for genetic induction of adult stem cell differentiation using microRNAs.