Stable carbon isotopes as indicators of increased water use efficiency and productivity in white spruce (Picea glauca (Moench) Voss) seedlings

The relationship among water use efficiency (WUE), productivity and carbon isotopic composition (δ¹³C) in white spruce (Picea glauca (Moench) Voss) seedlings was investigated. Sixteen hundred seedlings representing 10 controlled crosses were planted in the field in individual buried sand-filled cylinders. The soil water content in the cylinders was measured using time domain reflectometry over two growing seasons and seedling water use determined by water balance. Two watering treatments were imposed: irrigation and dry land. There was significant (1.6–2.0%c) genetic variation in needle δ¹³C. Ranking of crosses in terms of δ¹³C was generally maintained over watering treatments and there was not a significant genetic versus environmental interaction. There was a positive correlation between δ¹³C and both intrinsic and long-term WUE (more positive δ¹³C with increased WUE) and between δ¹³C and productivity, suggesting a correlation due to variation in photosynthetic capacity. Root to shoot ratios did not increase in water-stressed plants, indicating that responses to drought were primarily at the level of gas exchange, rather than through morphological changes. Our results indicate that it should be possible to use δ¹³C as a surrogate for WUE and to select white spruce genotypes for high WUE without compromising yield.     

Conversion of catechin and tannic acid by an enzyme preparation from Trametes versicolor

Summary An extracellular enzyme preparation produced by the white rot fungus Trametes versicolor transformed catechin and tannic acid. Optimum conversion of catechin was at 60°C and pH 6.0.     

Somaclonal variation as a tool to develop pest resistant plants of Torenia fournieri ‘Compacta Blue’

Callus cultures of Torenia fournieri Compacta Blue were initiated on a modified Murashige and Skoog salt medium (MS) with 2.26 M 2,4-dichlorophenoxyacetic acid. Shoots were regenerated from these cultures using MS medium amended with 2.46 M indolebutyric acid and 8.88 M benzyladenine. These shoot cultures were subjected to two-spotted spidermite (Tetranychus urticae Koch.) and the greenhouse whitefly [Trialeurodes vaporariorum (Westwood)]. Pests were allowed to feed until such time that their populations started to decrease due to lack of food. The remaining live tissue of the Torenia was placed on MS medium amended with 2.28 M zeatin to induce new adventitious shoots and plantlets. Newly regenerated plantlets were acclimated to greenhouse conditions and evaluated for resistance to the pest to which they were subjected in vitro. Highly significant differences in pest numbers were found in somaclones for both the two-spotted spidermite and greenhouse whitefly when compared to control plants. A wide range of variability was observed among the somaclonal population. There were significantly fewer mite eggs laid on plants regenerated from in vitro cultures screened with two-spotted spidermites than on seed sown controls. Regenerants from cultures screened with whiteflies in vitro had fewer eggs, immatures and live adults than controls.Abbreviations BA benzyladenine - IBA indolebutyric acid - 2,4-d 2,4-dichlorophenoxyacetic acid - MS Murashige and Skoog salt medium Storrs Agricultural Research Station Scientific Publication 1641.     

Oligomerization of uridine phosphorimidazolides on montmorillonite: A model for the prebiotic synthesis of rna on minerals

The 5-phosphorimidazolide of uridine reacts on Na⁺-montmorillonite 22A in aqueous solution to give oligomers as long as 7 mers. The maximum chain length increases to 9 mers and the overall oligomer yield increases when 9:1 ImpU, A⁵ ppA mixtures react under the same conditions. The oligomer yield and maximum chain length decreases with the structure of the added pyrophosphate in the order A⁵ ppA>A⁵ ppU>U⁵ ppU. Structure analysis of individual oligomer fractions was performed by selective enzymatic hydrolyses followed by HPLC analysis of the products. The regioselectivity for 3,5-bond formation is 80–90% in the 9:1 ImpU, A⁵ ppA reaction, a percentage comparable to that observed in the 9:1 ImpA, A⁵ ppA reaction. Oligomerization of ImpU is inhibited by addition of dA⁵ ppdA, and MeppA. No oligomers containing A⁵ ppU were products of the 9:1 ImpU, A⁵ ppA reaction, a finding consistent with the simple addition of the ImpU to the A⁵ ppA and not the rearrangement of an ImpU-A⁵ ppA adduct. Concentrations of lysine or arginine which were close to that of the ImpU did not inhibit oligomer formation. Treatment of Na⁺-montmorillonite with 1 M arginine yielded arginine-montmorillonite, an amino acid-mineral adduct which did not catalyze ImpU oligomerization. Neither the 4–9 mers formed in the 9:1 ImpU, A⁵ ppA reaction nor the 4–9 mers formed by the base hydrolysis of poly(U) served as templates for the formation of oligo(A)s.     

Sequence requirements for the recognition of tyrosine-based endocytic signals by clathrin AP-2 complexes.

We recently determined that fusion proteins containing tyrosine-based endocytic signals bind to the mu 2 subunit of AP-2, the complex that drives clathrin coat formation and mediates endocytosis from the plasma membrane. Here we analyze the selectivity of peptide recognition by mu 2 and by AP-2 using combinatorial selection methods and surface plasmon resonance. Both mu 2 and AP-2 are shown to interact with various sequences of the form tyrosine-polar-polar-hydrophobic (Yppø) found on receptors that follow the clathrin pathway. The optimal sequence for interaction with mu 2 and with AP-2 has tyrosine as an anchor and prefers arginine at position Y + 2 and leucine at position Y + 3. In contrast, no preferred sequence is detected surrounding the Yppø signal, indicating that recognition of the Yppø endocytic signal does not require a prefolded structure. We conclude that sorting into the endocytic pathway is governed by a surprisingly simple interaction between the mu 2 chain and a tyrosine-containing tetrapeptide sequence.     

Use of chicken microsatellite markers in turkey: a pessimistic view

Eighty-eight chicken microsatellite markers, previously developed in our laboratory, were tested for their ability to amplify polymorphic fragments using turkey genomic DNA. Amplification products were obtained for 61 chicken microsatellite markers (69.1%) whereas 27 (30.9%) did not give rise to any products, even when different polymerase chain reaction conditions were employed. From the 61 markers that gave a product, only eight showed a length polymorphism while 37 were monomorphic on the three divergent commercial turkey lines used. The remaining 16 markers yielded many unspecific bands and no specific amplification product could be obtained. Five polymorphic and eleven monomorphic products contained a detectable microsatellite repeat. Furthermore, of the markers that detected a polymorphism in turkey, the observed heterozygosity (15–50%) and allelic variation (only 2 in most cases) was very low. Therefore, on the basis of our results, we think that chicken microsatellite markers are not very useful for mapping purposes in turkey.     

Factors affecting transient gene expression in cultured radiata pine cotyledons following particle bombardment

Transfer and expression of the β–glucuronidase gene ( gusA ) in cultured cotyledons of radiata pine ( Pinus radiata D. Don ) were obtained by particle bombardment. Conditions for optimum transient expression were established by using plasmid pB[/12], delivered by gold particles, 1.6 μm in diameter, into 8-day-old cultured cotyledons. Helium pressure of 7.6 MPa, bombardment distance between the stopping screen and the target tissues of 6 cm, and 0.8 μg of plasmid DNA per bombardment proved to be the best parameters for transient expression; using these parameters 79% of bombarded cotyledons showed GUS activity, with 4.3 blue spots per cotyledon. This system was used for studying the expression of several gus-driven promoters the expression of the sunflower ubiquitin gene promoter was higher (99% of positive cotyledons, with 14.2 blue spots per cotyledon) than that of the CaMV 35S promoter, whereas the rice actin and the maize alcohol dehydrogenase gene promoters gave lower gusA expression, as determined histochemically. These results were confirmed by using the gus fluorometric assay. Use of the sunflower ubiquitin gene promoter resulted in gusA expression up to 20 days after bombardment, with a significant level of gus expressing loci per bombarded cotyledon, whereas with the CaMV 35S promoter gusA expression was lost 12 days after bombardment.