Book reviews

Ohne Zusammenfassung

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Book reviews

     

Über den Einfluß von Kinetin auf den Coffeingehalt der Blätter von Coffea arabica L.

Summary Kinetin induces an increase in the caffeine content of Coffea leaves of up to 40% of the normal level. The effect is most pronounced in young leaves; it is, however, transient. After six days in old leaves and after 12 days in young leaves, the caffeine content has decreased to its normal level.The results are discussed in relation to the recently discovered fact that cytokinins kinins are constituents of rare nucleotides of seryl-t-RNA. It seems plausible that the methylations necessary in the synthesis of caffeine are linked with this primary function of cytokinins.     

P-related sequences inDrosophila bifasciata: A molecular clue to the understanding of P-element evolution in the genusDrosophila

Summary Two P-elements (bif1 and bif2) were isolated from a genomic library ofDrosophila bifasciata. Both elements are internally deleted and have lost the coding capacity for a functional transposase. One of the elements (bif2) contains an insert consisting of a repetitive sequence. The terminal inverted repeats and the segments necessary for passive mobility are well conserved. Element bif2 has retained rudiments of the coding sequence of exon 0 and exon 3, but the reading frame is destroyed by insertions and deletions. The comparison of theD. bifasciata P-elements with P-elements ofDrosophila melanogaster andDrosophila nebulosa reveals that the two latter sequences are more similar to each other than either of them is to theD. bifasciata elements. This finding contradicts the phylogenetic relationship of the species and can be taken as an indirect but unequivocal evidence for recent horizontal gene transfer from a relative ofD. nebulosa to the gene pool ofD. melanogaster. The P-elements ofD. bifasciata are phylogenetically ancient and have evolved independently for about 50 million years. A higher substitution rate at the third codon position as well as a predominance of conservative replacements at the amino acid level indicates that the P-elements ofD. bifasciata have been under selective constraint over a long period and that immobilization has occurred only recently.     

Repeated horizontal transfer of P transposons between Scaptomyza pallida and Drosophila bifasciata

Two distinct P element subfamilies, designated M-type and O-type, reside in the genome of D. bifasciata. PCR-screening of 65 Drosophila species revealed that only D. bifasciata and its closest relative D. imaii possess O-type elements. Outside the genus, O-type elements were detected in Scaptomyza pallida. Restriction analyses show that the general structure of the O-type elements from S. pallida and D. bifasciata is the same. Sequence divergence turned out to be extremely low (0.43%). These results suggest that the O-type subfamily of D. bifasciata has been received by horizontal transfer from an external source, most probably from the genus Scaptomyza, as has been previously suspected for the M-type family. Since the sequence divergence between M-type elements from S. pallida and D. bifasciata is eighteenfold higher than that between O-type elements, two independent intergeneric transfer events have to be postulated. In order to re-examine the taxonomic status of S. pallida, a partial sequence (489 bp) of the Adh gene was analysed. The data clearly prove that S. pallida has to be placed far outside the D. obscura group.     

Kritische Untersuchungen über die Organisation des Sproßscheitels dikotyler Pflanzen

Ohne Zusammenfassung     

Synthesis of glucosylglycerol in salt-stressed cells of the cyanobacterium Microcystis firma

The unicellular cyanobacterium Microcystis furma tolerates salinity by accumulating the osmoprotective compound glucosylglycerol. After salt shock, the initial rate of glucosylglycerol synthesis is independent of the NaCl concentration used. In pulse chase experiments with NaH¹⁴CO₃, synthesis of glucosylglycerol by salt-adapted cells was found to be rapid, whereas no sign of its breakdown was detected. Therefore, it is concluded that no turnover of glucosylglycerol takes place in salt-adapted cells. The specific capacity of the glucosylglycerol-forming enzyme system may be one reason for the salt resistance limit.Abbreviation GG glucosylglycerol Dedicated to Prof. Dr. Eike Libbert on the occasion of his 60th birthday     

Furosemide exhibits physicochemical properties similar to prostaglandins and interferes with their bioassay

The parallel pharmacological assay system has been of inestimable value in the identification and quantification of prostaglandins. A greater degree of specificity is conferred on the bioassay system by the preparative techniques of extraction and chromatography, for substances which might interfere with the assay of prostaglandins are usually eliminated by these procedures. It would be highly unlikely for a substance to survive the extraction procedure, to exhibit chromatographic properties similar to the prostaglandins and to interfere with their bioassay. We report here such an occurrence. Thus, furosemide not only survived the acidic lipid extraction, but, in addition, it exhibited chromatographic properties identical to those of the prostaglandins of the E series and finally, furosemide, at a dose which in and of itself was without effect on the assay tissues, inhibited the responses to prostaglandins. The quantification of prostaglandins by radioimmunoassay was, on the other hand, not altered by the presence of furosemide. This latter method appears to be the one of choice when interrelations between prostaglandins and furosemide are being examined.     

Contribution of Glucosinolate Transport to Arabidopsis Defense Responses

Accumulation of glucosinolates, a class of defense-related secondary metabolites found almost exclusively in the Capparales, is induced in response to a variety of biological stresses. It is often assumed that elevated glucosinolate levels result from de novo biosynthesis, but glucosinolate transport from other parts of the plant to the site of herbivory or pathogen infection can also contribute to the defense response. Several studies with Arabidopsis and other crucifers have demonstrated that glucosinolates from vegetative tissue are transported to developing seeds. Here we discuss evidence that long-chain aliphatic glucosinolates are transported to the site of herbivory in response to Myzus persicae (green peach aphid) feeding on Arabidopsis.Key Words: glucosinolate, transport, graft, Arabidopsis, Myzus persicae, aphid