Somaclonal variation in soybean plants regenerated from tissue culture

Callus cultures of soybean (Glycine max (L.) Merr.) genotypes PI 88788, PI 438489B, and cultivar Bedford were initiated in vitro from seedling explants consisting of the cotyledonary node plus epicotyl from germinated mature seed. Plants were regenerated from these callus cultures and subsequently evaluated for qualitative variation in three to four subsequent generations. Variant phenotypes observed that have not been previously reported from tissue culture include lanceolate leaves, leaf variegation (chimeral variegated plants), pod variegation on otherwise normal plants, and change in growth habit from indeterminate to determinate. The lanceolate leaf, chimeral variegated plant, and change from indeterminate to determinate growth habit characters were inherited through at least three generations (R₀-R₂), and segregation occurred in each generation. Pod variegation was inherited through the two generations tested thus far and segregation occurred in each generation. No variation was observed in control plants derived from normal seed. Variants appeared more frequently in regenerants from PI 88788 and PI 438489B than from Bedford. These results confirm and extend the finding that certain tissue culture techniques may be used to induce novel plant formation from somatic tissue of soybean.Missouri Agricultural Experiment Station, University of Missouri, Columbia, Missouri, USAMention of tradenames does not constitute a guarantee or warranty of the product by University of Missouri or USDA-ARS and does not imply their approval to the exclusion of other products.     

Studies on site directed mutant pig citrate synthases

The DNAs encoding the non-mutant and mutant forms of pig citrate synthase (PCS) were subcloned into an expression system to determine their synthesis and stability in E. coli gltA- cells that are defective in bacterial citrate synthase. GltA- cells that expressed the non-mutant PCS DNA grew on defined minimal acetate media and produced a constant level of PCS (0.43 U/mg protein). In contrast, when the gltA- cells were transformed with the DNA encoding PCS mutations in His274 or Asp375 the cells did not grow on minimal acetate media. The presence of the mutant PCS proteins in E. coli was confirmed by protein blot and immunoisolation analyses using an antibody specific for porcine heart citrate synthase. The activities of the mutant PCS enzymes were two orders of magnitude less than the non-mutant enzyme in the total cell lysates. The data indicate that the active site amino acids, His274 and Asp375, are essential for the catalysis activity of citrate synthase.     

Are subspecies useful in evolutionary and conservation biology?

The taxonomic rank of subspecies remains highly contentious, largely because traditional subspecies boundaries have sometimes been contradicted by molecular phylogenetic data. The most complete meta-analysis to date, for instance, found that only 3% of traditional avian subspecies represented distinct phylogenetic lineages. However, the global generality of this phenomenon remains unclear due to this previous study's narrow geographic focus on continental Nearctic and Palearctic subspecies. Here, we present a new global analysis of avian subspecies and show that 36% of avian subspecies are, in fact, phylogenetically distinct. Among biogeographic realms we find significant differences in the proportion of subspecies that are phylogenetically distinct, with Nearctic/Palearctic subspecies showing significantly reduced levels of differentiation. Additionally, there are differences between island and continental subspecies, with continental subspecies significantly less likely to be genetically distinct. These results indicate that the overall level of congruence between taxonomic subspecies and molecular phylogenetic data is greater than previously thought. We suggest that the widespread impression that avian subspecies are not real arises from a predominance of studies focusing on continental subspecies in North America and Eurasia, regions which show unusually low levels of genetic differentiation. The broader picture is that avian subspecies often provide an effective short-cut for estimating patterns of intraspecific genetic diversity, thereby providing a useful tool for the study of evolutionary divergence and conservation.     

Structure-activity relationship of the neurotransmitter alpha-bag cell peptide on Aplysia LUQ neurons: Implications regarding its inactivation in the extracellular space

Alpha-bag cell peptide [α-BCP (Ala-Pro-Arg-Leu-Arg-Phe-Tyr-Ser-Leu)] is a neurotransmitter that mediates bag cell-induced inhibition of left-upper-quadrant (LUQ) neurons L₂, L₃, L₄, and L₆ in the abdominal ganglion of Aplysia. Our recent biochemical studies have shown that α-BCP[1–9] is cleaved into α-BCP[1–2], [3–9], [1–5], [6–9], and [7–9] by a combination of three distinct peptidase activities located within the extracellular spaces of the CNS: A diaminopeptidase-IV (DAP-IV)-like enzyme cleaves α-BCP[1–9] at the 2–3 peptide bond; a neutral metalloendopeptidase (NEP)-like enzyme cleaves either α-BCP[1–9] or α-BCP[3–9] at the 5–6 bond; an aminopeptidase M-II (APM-II)-like enzyme cleaves α-BCP[6–9] at the 6–7 bond, but cleaves neither α-BCP[1–9], nor the other ganglionic peptidase products. To further understand the manner in which α-BCP is inactivated after release, that is loses its electro-physiological activity, we studied its structure-activity relationship by recording intracellularly from LUQ neurons in isolated abdominal ganglia that were arterially perfused with peptides dissolved in artificial sea water. The effects of α-BCP[1–9] and 15 of its fragments ([1–8], [1–7], [1–6], [1–5], [2–9], [3–9], [3–8], [6–9], [7–9], [8–9], [6–7], [6–8], [1–2], Phe, Tyr) indicated that the sequence Phe⁶-Tyr⁷ was both necessary and sufficient to produce LUQ inhibitory activity. The combined results of our electrophysiological and biochemical studies strongly suggest that α-BCP[1–9] is inactivated by the serial actions of the NEP-like and APM-II-like peptidases; that is, the NEP-like enzyme yields an electro-physiologically active product, α-BCP[6–9], that is cleaved by the APM-II-like enzyme to yield inactive α-BCP[7–9]. Furthermore, because α-BCP[6–9] is more active than α-BCP[1–9], cleavage by the NEP-like enzyme potentiates α-BCP's activity. © 1992 John Wiley & Sons, Inc.     

Growth and development of conifer pollen tubes

Conifer pollen tubes are an important but underused experimental system in plant biology. They represent a major evolutionary step in male gametophyte development as an intermediate form between the haustorial pollen tubes of cycads and Ginkgo and the structurally reduced and faster growing pollen tubes of flowering plants. Conifer pollen grains are available in large quantities, most can be stored for several years, and they grow very well in culture. The study of pollen tube growth and development furthers our understanding of conifer reproduction and contributes towards our ability to improve on their productivity. This review covers taxonomy and morphology to cell, developmental, and molecular biology. It explores recent advances in research on conifer pollen and pollen tubes in vivo, focusing on pollen wall structure, male gametophyte development within the pollen wall, pollination mechanisms, pollen tube growth and development, and programmed cell death. It also explores recent research in vitro, including the cellular mechanisms underlying pollen tube elongation, in vitro fertilization, genetic transformation and gene expression, and pine pollen tube proteomics. With the ongoing sequencing of the Pinus taeda genome in several labs, we expect the use of conifer pollen tubes as an experimental system to increase in the next decade.     

Design and synthesis of a new class of malonyl-CoA decarboxylase inhibitors with anti-obesity and anti-diabetic activities

A new series of thiazole-substituted 1,1,1,3,3,3-hexafluoro-2-propanols were prepared and evaluated as malonyl-CoA decarboxylase (MCD) inhibitors. Key analogs caused dose-dependent decreases in food intake and body weight in obese mice. Acute treatment with these compounds also led to a drop in elevated blood glucose in a murine model of type II diabetes.     

Structure-activity relationship of the neurotransmitter alpha-bag cell peptide on Aplysia LUQ neurons: implications regarding its inactivation in the extracellular space.

Alpha-bag cell peptide [alpha-BCP (Ala-Pro-Arg-Leu-Arg-Phe-Tyr-Ser-Leu)] is a neurotransmitter that mediates bag cell-induced inhibition of left-upper-quadrant (LUQ) neurons L2, L3, L4, and L6 in the abdominal ganglion of Aplysia. Our recent biochemical studies have shown that alpha-BCP[1-9] is cleaved into alpha-BCP[1-2], [3-9], [1-5], [6-9], and [7-9] by a combination of three distinct peptidase activities located within the extracellular spaces of the CNS: A diaminopeptidase-IV (DAP-IV)-like enzyme cleaves alpha-BCP[1-9] at the 2-3 peptide bond; a neutral metalloendopeptidase (NEP)-like enzyme cleaves either alpha-BCP[1-9] or alpha-BCP[3-9] at the 5-6 bond; an aminopeptidase M-II (APM-II)-like enzyme cleaves alpha-BCP[6-9] at the 6-7 bond, but cleaves neither alpha-BCP[1-9], nor the other ganglionic peptidase products. To further understand the manner in which alpha-BCP is inactivated after release, that is loses its electrophysiological activity, we studied its structure-activity relationship by recording intracellularly from LUQ neurons in isolated abdominal ganglia that were arterially perfused with peptides dissolved in artificial sea water. The effects of alpha-BCP[1-9] and 15 of its fragments ([1-8], [1-7], [1-6], [1-5], [2-9], [3-9], [3-8], [6-9], [7-9], [8-9], [6-7], [6-8], [1-2], Phe, Tyr) indicated that the sequence Phe6-Tyr7 was both necessary and sufficient to produce LUQ inhibitory activity.(ABSTRACT TRUNCATED AT 250 WORDS)