Auxin-induced rapid changes in translatable mRNAs in tobacco cell suspension

When 2,4-dichlorophenoxyacetic acid (2,4-D)-dependent tobacco cell suspensions, one normal and one transformed by Agrobacterium tumefaciens, were subcultured on hormone-lacking medium the stationary phase of the cell cycle was reached earlier than on medium containing 2,4-D. Addition of the auxin 2,4-D could restore cell division activity within 10–12 h for the most rapidly reacting cell line. The cell-division response was characterized as being auxin-specific and optimal with 2,4-D at 2.2 10^-6 M. Although the cell lines used showed different characteristics, both reacted with a rapid increase in at least three mRNA species within 1 or 2 h after 2,4-D application. Two, 2,4-D-induced protein spots, seen after in-vitro translation, had the same characteristics (MWs 35 kilodaltons (kDa) and 25 kDa with isoelectric points of 7.1 and 6.3, respectively) in both cell lines. Water-treated controls did not show alterations in the translatable mRNA populations. This indicates that the accumulation of the corresponding mRNAs is an early hormone-induced event. Since cell division is the only measurable reaction found after auxin application, cell systems as described here offer excellent possibilities for studying early auxin-induced changes at the molecular level preceding mitosis.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indole-3-acetic acid - kDa kilodalton     

Somatic instability of carotenoid biosynthesis in the tomato ghost mutant and its effect on plastid development

The tomato (Lycopersicon esculentum (L.) Mill.) ghost plant is a mutant of the San Marzano cultivar affected in carotenoid biosynthesis. ghost plants exhibit a variable pattern of pigment biosynthesis during development. Cotyledons are green but true leaves are white. Green sectors, which appear to be clonal in origin, are frequently observed in the white tissue. Because of the lack of photosynthesis ghost plants have a very low viability in soil. We have developed a strategy for propagating ghost plants that employs organ culture to generate variegated green-white plants which, supported by the photosynthetic green areas, develop in soil to almost wild-type size. These plants were used to analyze the pigment content of the different tissues observed during development and plastid ultrastructure. Cotyledons and green leaves contain both colored carotenoids and chlorophyll but only the colorless carotenoid phytoene accumulates in white leaves. the plastids in the white tissue of ghost leaves lack internal membrane structures but normal chloroplasts can be observed in the green areas. The chromoplasts of white fruits are also impaired in their ability to form thylakoid membranes.     

Evolution des glucides intratissulaires au cours de la néoformation des bourgeons par des explantats racinaires de Cichorium intybus cultivés in vitro

Variation of intratissular carbohydrates during bud formation in root explants of Cichorium intybus cultivated in vitro .
During the cellular activation that begins with excision of root explants from Cichorium intybus L. var. Witloof cv. Zoom cultured in vitro, hydrolysis of fructose polymers, in particular of the polyfructosans (inulin) takes place. The products of degradation are used to cover the energetic needs connected with the increase of the mitotic activity. After day 2 the intracellular carbohydrates (sucrose and reducing sugars) develop differently according to further development of the explants. When growth of unorganized callus is favoured and organ formation inhibited by medium supplemented with auxin, fructose is accumulated; but under bud-forming conditions it is the amount of sucrose that increases. These differences were most notable between days 3 and 10 in culture, the period during which primordia occurred in the shoot-forming callus     

Diagnosis of iron deficiency in groundnut,Arachis hypogaea L.

Summary Investigations into iron deficiency have been hindered by the lack of a satisfactory diagnostic tissue test, which in turn results from the total iron content of plant tissue commonly being an unreliable index of the iron status. Our measurements of chlorotic and normal leaves of field grown groundnut (Arachis hypogaea L.) showed that total iron was unsatisfactory as the measure of iron status of plant tissue. It was found that iron status was better assessed from an estimate of the ferrous iron content of fresh leaf materials obtained by extraction with o-phenanthroline. Extractable iron content increased with leaf age. Chlorotic buds or the first fully opened leaf always contained less than 6μg extractable-Fe/g fresh tissue. Approved for publication as ICRISAT Journal Article No. 307.     

Selection for components related to body composition in mice: direct responses

Summary Replicated within full-sib family single-trait selection was conducted for 10 generations in mice for (1) high or low 12-week epididymal fat pad percentage (100 x epididymal fat pad weight/body weight) or (2) high or low 12-week hind carcass percentage (100 x hind carcass weight/body weight). Pooled realized heritabilities based on high, low and divergent selection were 0.66±0.09, 0.65±0.13 and 0.66±0.05 for epididymal fat pad percentage and 0.48±0.08, 0.33±0.08 and 0.40±0.04 for hind carcass percentage. The pooled realized genetic correlation (r_{G R}) between epididymal fat pad percentage and hind carcass percentage based on divergence was –0.67±0.04. Other estimates of (r_{G R}) were: epididymal fat pad percentage with body weight (0.57±0.05); epididymal fat pad percentage with epididymal fat pad weight (1.17±0.05); hind carcass percentage with body weight (–0.61±0.09); hind carcass percentage with hind carcass weight (–0.05±0.11). Indirect measures of fat and lean tissue percentages were highly heritable, and (r_{G R}) between them would be desirable from the standpoint of analogous types of traits in livestock. In the same context, undesirable (r_{G R})'s were found between epididymal fat pad percentage and body weight and between hind carcass percentage and body weight.Paper No. 10957 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina 27695-7601, USA. The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the products named, nor criticism of similar ones not mentioned     

Isolation of tomato cell lines with altered response to Fusarium cell wall components

Summary To obtain Tomato cell lines with an altered capacity to respond to heat-released cell wall components (elicitor) of a tomato pathogen (Fusarium oxysporum f. sp. lycopersici), positive and negative selection experiments, using BUdR enrichment techniques, were carried out on suspension cultures of the susceptible, low phytoalexin producer cultivar Red River. Both high and low phytoalexin producing clones were isolated. Further tests demonstrated that not all phytoalexin-producing clones were more susceptible to the elicitor toxic effect, and that they were altered also in the speed of response to fungal cell wall components. Cells selected with Fusarium elicitor showed the same behaviour when challenged by Phytophthora infestans elicitor, thus suggesting in this case lack of specificity. The results are finally discussed with a view to using the technique both as a tool to study the genetics and physiology of hostparasite interactions and as a possible new method for the selection of pathogen resistant genotypes.Paper no. 1224 IPRA-CNR; research supported by an EEC-BAP contract     

Standard dimensions forcis N-methyl peptide unit and flexibility ofcis peptide units

The mean dimensions of thecis N-methyl peptide unit have been arrived at by analysing the crystal structure data on compounds containing such units. These dimensions can be used as standard in conformational studies on cyclic peptides. While the bonds meeting at C are almost coplanar, those meeting at N show a slight pyramidal disposition. A comparison of the dimensions of the normal and N-methylatedcis peptide units show that there are perceptible differences in the parameters connected with N. In addition, the flexibility of thecis peptide unit has been analysed by studying the distribution of the parameters in different classes of compounds such as cyclic di, tri and higher peptides. The salient features are: (i) The angle C^αCN in cyclic dipeptide and the angle C^δNC^α in higher peptides tend to be lower, when the peptide unit is associated with a prolyl residue; (ii) in cyclic tripeptides the internal anglesviz., C^αCN and CNC^α are significantly larger thereby increasing the intra-annular space; (iii) the bond C^α-C is distinctly shorter when it occurs in cyclic dipeptides. The results lead to the conclusion that thecis peptide unit takes up aneed-based flexibility in its dimension.     

Reactivity of glycoconjugate in membrane system II: Can a neutral glycolipid function as lectin receptor in the presence of gangliosides in plasma membrane?

To examine how surface Potential controls the reactivity of glycoconjugates at cell surface, the interaction of galactose-sPecific lectinse.g. peanut agglutinin,Ricinus cummunis agglutinin with liPosomes bearing asialo GM₁ were studied in the Presence of varying amount of ganglioside mixture, GM_n. The Presence of 5% GM_n causes comPlete slowing down of PreciPitin reaction and thereby make carbohydrate moiety of asialo GM₁ comPletely inaccessiblei.e. ‘cryPtic’. In contrast the Presence of 1–2% GM_n enhances the aPParent rate and amPlitude of the PreciPitin reaction as surface Potential becomes more negative. The relevance of the findings has been discussed in relation to the exPression and involvement of the cell-surface sialic acid residues during develoPment and differentiation.     

Subcellular Location and Neuronal Release of Diazepam Binding Inhibitor

Diazepam binding inhibitor (DBI), a peptide located in CNS neurons, blocks the binding of benzodiazepines and beta-carbolines to the allosteric modulatory sites of gamma-aminobutyric acid (GABAA) receptors. Subcellular fractionation studies of rat brain indicate that DBI is compartmentalized. DBI-like immunoreactivity is highly enriched in synaptosomes obtained by differential centrifugation in isotonic sucrose followed by a Percoll gradient. In synaptosomal lysate, DBI-like immunoreactivity is primarily associated with synaptic vesicles partially purified by differential centrifugation and continuous sucrose gradient. Depolarization induced by high K+ levels (50 mM) or veratridine (50 microM) released DBI stored in neurons of superfused slices of hypothalamus, hippocampus, striatum, and cerebral cortex. The high K+ level-induced release is Ca2+ dependent, and the release induced by veratridine is blocked by 1.7 microM tetrodotoxin. Depolarization released GABA and Met5-enkephalin-Arg6-Phe7 together with DBI. DBI is also released by veratridine depolarization, in a tetrodotoxin-sensitive fashion, from primary cultures of cerebral cortical neurons, but not from cortical astrocytes. Depolarization fails to release DBI from slices of liver and other peripheral organs. These data support the view that DBI may be released as a putative neuromodulatory substance from rat brain neurons.