Similarity of maize and sorghum genomes as revealed by maize RFLP probes

Summary Densely saturated genetic maps of neutral genetic markers are a prerequisite either for plant breeding programs to improve quantitative traits in crops or for evolutionary studies. cDNA and genomic clones from maize were utilized to initiate the construction of a RFLP linkage map in Sorghum bicolor. To this purpose, an F₂ population was produced from starting parental lines IS 18729 (USA) and IS 24756 (Nigeria) that were differentiated with regard to many morphological and agronomical traits. A total of 159 maize clones were hybridized to the genomic DNA of the two parents in order to detect polymorphism: 154 probes hybridized to sorghum and 58 out of these were polymorphic. In almost all of the cases hybridization patterns were similar between maize and sorghum. The analysis of the segregation of 35 polymorphic clones in an F₂ population of 149 individuals yielded five linkage groups. The three principal ones recall regions of maize chromosomes 1, 3 and 5: in general, colinearity was maintained. A possible inversion, involving a long region of maize chromosome 3, was detected. Simulations were also performed to empirically obtain a value for the lowest number of individuals of the F₂ population needed to obtain the same linkage data.Prof. E. Ottaviano, to whom this paper is dedicated, suddenly died on June 7^th, 1991     

Characterization of a major brain tubulin variant which cannot be tyrosinated

Brain tubulin preparations contain an abundant type of tubulin which does not undergo the normal cycle of tyrosination-detyrosination, and whose nature is still unknown. We have used peptide sequence analysis and mass spectrometry combined with immunological procedures to show that this non-tyrosinatable tubulin has a specific primary structure. It differs from the tyrosinated isotype in that it lacks a carboxy-terminal glutamyl-tyrosine group on its alpha-subunit. Thus, non-tyrosinatable tubulin originates from a well-defined posttranslational modification of the tubulin primary structure which is located at the expected site of activity of tubulin tyrosine ligase. This probably accounts for the reason why it cannot be tyrosinated. The significance of this abundant brain isotubulin and the metabolic pathway involved in its formation remain to be elucidated. This should shed light on the relation between the structural diversity of the carboxy terminus of alpha-tubulin and the regulation of functional properties of microtubules.     

Identification of 'cystic fibrosis protein' as a complex of two calcium-binding proteins present in human cells of myeloid origin

Cystic fibrosis protein is a serum protein characterized by a pI close to 8.4 and present with a higher concentration in serum and plasma of cystic fibrosis carriers than in controls. This protein was found immunologically indistinguishable from the cystic fibrosis antigen isolated from granulocytes and presenting a sequence analogous to that of MRP-8, a calcium-binding protein expressed in the myeloid cell lineage. Using antibodies directed against MRP-8 and its closely associated calcium-binding protein, MRP-14, we demonstrate here that cystic fibrosis protein purified from serum is a complex of the two proteins MRP-8 and MRP-14.     

The electrical and spectroscopic properties of planar asymmetrical membranes incorporating chlorophyll a and plastoquinone-9. Model of incorporation of chlorophyll a and plastoquinone-9

We have studied the incorporation of chlorophyll a and plastoquinone-9 in Montal-Mueller membranes. In particular, we have been interested by the influence of both the lipid : chlorophyll a ratio and the asymmetry of incorporation of the constituents on the electrical and fluorescence spectroscopic properties of the planar membranes built up from these constituents. The phospholipid matrix was made from phosphatidylethanolamine and phosphatidylserine. The monitoring of the fluorescence spectral properties of chlorophyll a incorporated in various concentrations leads to the conclusion that chlorophyll a is incorporated in the bilayers in monomeric form inside microdomains. It is shown that chlorophyll a is positioned in these microdomains in such a way that the porphyric ring is interacting with the polar head of the lipid molecules where the interface polarity shows a dielectric constant varying between 25 and 35. The phytyl chain is embedded in the bilayer core, serving as an anchor, running parallel to the aliphatic chains of the phospholipids. We have also monitored the position of the plastoquinone-9 molecules within the bilayer. We found that plastoquinone-9 is incorporated in the center plane of the bilayer, increasing the thickness of the bilayer. This result confirms evidence, gathered in the literature from monolayer and differential scanning calorimetry studies, that long chain quinones and especially plastoquinone-9 are embedded deeply within the hydrophobic core of the bilayer. We also show that when chlorophyll a and plastoquinone-9 are present together in the bilayer, the quinolic ring of the plastoquinone-9 molecule positions itself in the free volume created by the bulky porphyric ring of a chlorophyll a molecule.     

On the purinergic system in rat duodenum: existence of P1 and P2 receptors on the smooth muscle.

In rat duodenum, in vitro, in the presence of atropine and guanethidine, ATP administration caused a tetrodotoxin-insensitive relaxation followed by a rebound contraction. A similar response was obtained also after electrical field stimulation (EFS) of non-adrenergic, non-cholinergic (NANC) nerves. alpha, beta-methylene-TP and theophylline antagonized the response to ATP, but they failed to affect the noradrenaline- and EFS-induced relaxation. These results suggest that P1 and P2 receptors are present in rat duodenum, but their activation is not responsible for the inhibitor effects due to the NANC nerves.     

Differential mitotic rates and patterns of growth in compartments in the Drosophila wing

In the wing disks of Drosophila slowly dividing cells of Minute mutations are progressively eliminated from Minute/Minute⁺ mosaic compartments by a process known as cell competition. From a study of two different Minutes we show here that the intensity of competition is greater in the more extreme Minute with the slowest rate of cell division. The way in which the more rapidly growing Minute⁺ clones grow and overcome the surrounding Minute cells is described and cell competition is shown to be a result of local interactions between slow- and faster-growing cells.     

Structural studies of the apoprotein of the Folch-Pi bovine brain myelin proteolipid : characterization of the CNBr-fragments and of a long C-terminal sequence.

The action of cyanogen bromide on the quite insoluble bovine proteolipid apoprotein allowed the determination of four peptide fragments: two of them constituted a 19 amino acid long C-terminal sequence of the apoprotein. Our results were in favour of the existence of only one subunit presenting a molecular weight closely related to 25,000 for which a schematic representation is given.