The role of nucleic acids in morphogenesis

Nucleic acid-selective light-up fluorescent biosensors for ratiometric two-photon imaging of the viscosity of live cells and tissues

Rational design of specific ratiometric viscosity probes with small molecular weight is a challenge in practical biotechnology applications. Herein two novel water-soluble, small-molecular ratiometric probes, bearing N-methyl benzothiazolium moiety (DSF and DBF), are designed for two-photon fluorescent imaging as a functional of local viscosity. The dye DSF, a light-up fluorescent probe, is sensitive to local viscosity and selectively stains nuclear DNA, which can be used to inspect asynchronous cells under confocal microscopy. While the dye DBF as a molecular rotor displays strong fluorescence enhancement in viscous media or binding to RNA. It exhibits dual absorption and emission as well, and only the red emission is markedly sensitive to viscosity changes, providing a ratiometric response and selectively imaging nucleolic and cytosolic RNA. Interestingly it is shown, for the first time, that the intracellular targeting and localization (DNA and RNA) of the two dyes are entirely realized simply by modifying the substituent attached to the benzothiazolium.

Recent development of two-photon fluorescent probes for bioimaging

Fluorescent probes are essential tools for studying biological systems.

[The activity of phosphoglucose-isomerase and phosphoglucomutase during morphogenesis of nucleate and anucleate cells of Acetabularia]

The activity of two enzymes of the UDP-glucose and UDP-galactose biosynthetic pathway-phosphoglucose-isomerase and phosphoglucomutase-have been followed during morphogenesis of the unicellular green alga Acetabularia mediterranea. We have found that the increase in enzyme activities during morphogenesis represents de novo synthesis. The kinetic constants (K m, K i) of phosphoglucose-isomerase are similar to those found for the enzyme from rabbit muscle; mannose-6-phosphate was found to be a competitive inhibitor.The increase in activity of phosphoglucose-isomerase parallels the linear increase in total protein, neither showing changes with cap formation. In contrast, the activity of phosphoglucomutase is enhanced markedly when cap formation starts.Whether the nucleus is present or absent does not affect the above mentioned properties of the two enzymes. From this fact we conclude that the enzyme syntheses are regulated by the cytoplasm, probably at the level of translation. Contributions of DNA from chloroplasts and mitochondria can be excluded because in anucleate cells, which have an already established gradient of m-RNA, actinomycin D (10 μg/ml) has no effect on the synthesis of these enzymes.There are also differences in the spatial distribution of the two enzymes. We were able to show that both enzymes are synthesized unequally in different regions of the cells.

[Uncoupling of morphogenetic processes in Acetabularia mediterranea by P-fluorophenylalanine]

1. Cap-formation of nucleated and enucleated plants of Acetabularia mediterranea was inhibited by 10-50 μg/ml p-fluorophenylalanine almost completely, while the formation of the stalk and whorls as well as protein synthesis is only slightly affected. 2. This selective inhibition of cap-formation by fluorophenylalanine is cancelled by phenylalanine or tyrosine. 3. The inhibition caused by flourophenylalanine is reversible if the plants are transferred into Erdschreiber medium without fluorophenylalanine before cap-formation starts. But the inhibition is largly (nucleated plants) or totally (enucleated plants) irreversible, if the back-transfer takes place after a large part of the control plants has finished cap-formation. 4. Plants which were exposed to fluorophenylalanine a few days before cap-formation is initiated are able to form a small cap, but further growth of the cap is stopped. 5. The following conclusions can be drawn from these results. The activities of the proteins which control stalk-and whorl formation in Acetabularia mediterranea are not influenced by the incorporation of p-fluorophenylalanine. On the other hand one or a few proteins which control cap-formation are inactivated by the incorporation of the fluorine-containing analogue. Therefore cap-formation is controlled by another set of enzymes and structural proteins than stalk-und whorl formation. 6. The synthesis of the proteins which are specific for cap-formation is started a few days before the actuel onset of cap-formation. Synthesis of these specific proteins is also necessary for the further growth of the cap.

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1 In vivo treatment with RNase considerably increases (80%) the RNA content of anucleate and nucleate fragments as well as of whole algae (Acetabularia mediterranea). A parallel increase in the incorporation of phenylalanine into proteins is observed. 2 Prolonged actinomycin (30 \gmg/ml) treatment (7\2-15 days) results in a decrease in the amount of RNA in whole algae and in anucleate apical fragments. This is not, however, the case for the basal anucleate fragments of the stalk. The fact that RNA synthesis in this region resists such treatment with actinomycin seems to bear some relation to the extreme limitation of their morphogenetic capacities. 3 The biological effects of RNase are increased by the simultaneous addition in vivo of actinomycin. 4 Thymus histones and polylysine influence morphogenesis in the same manner as actinomycin though to a lesser extent. 5 Anucleate fragments are much more sensitive than the nucleate fragments to levorphanol, which probably inhibits preferentially ribosomal RNA synthesis. 6 The significance of these results is discussed.