Putrescine Influences Growth and Production of Coumarins in Hairy Root Cultures of Witloof Chicory (Cichorium intybus L. cv. Lucknow Local)

The effect of putrescine (Put) on the growth and production of two coumarins, esculin and esculetin, in hairy roots of chicory (Cichorium intybus L. cv. Lucknow local) was examined. To study the role of Put on growth and production of coumarins, polyamine inhibitors, namely α-dl-difluromethylornithine and α-dl-difluromethylarginine were used at 1 mM concentration. Put treatment at 1.5 mM produced a 1.9-fold increase in the growth of hairy roots, as well as the production of esculin and esculetin. The treatments with polyamine (PA) inhibitors resulted in much lower growth and production of coumarins compared with both 1.5-mM Put treatment and the control. Both free and conjugated PAs were studied over the whole culture period, and conjugates of all three PAs, namely Put, spermidine, and spermine, were higher than free PAs throughout the culture period. The treatments with PA inhibitors showed lower levels of endogenous PAs compared with Put-treated samples. The treatment with 1.5 mM Put showed maximum accumulation of endogenous conjugated Put (2,098 ± 157 nmoles gm⁻¹ fresh weight). The production of esculin and esculetin was strictly correlated with growth in all treatments. Put at 1.5 mM resulted in greater length of primary root (18.3 ± 1.4 cm) as compared with the control (11 ± 0.9 cm) and larger numbers of secondary and tertiary roots. Received July 14, 1999; accepted October 5, 1999     

Oxalate contributes to the resistance of Gaillardia grandiflora and Lupinus sericeus to a phytotoxin produced by Centaurea maculosa

Centaurea maculosa Lam. is a noxious weed in western North America that produces a phytotoxin, (±)-catechin, which is thought to contribute to its invasiveness. Areas invaded by C. maculosa often result in monocultures of the weed, however; in some areas, North American natives stand their ground against C. maculosa and show varying degrees of resistance to its phytotoxin. Two of these resistant native species, Lupinus sericeus Pursh and Gaillardia grandiflora Van Houtte, were found to secrete increased amounts of oxalate in response to catechin exposure. Mechanistically, we found that oxalate works exogenously by blocking generation of reactive oxygen species in susceptible plants and reducing oxidative damage generated in response to catechin. Furthermore, field experiments show that L. sericeus indirectly facilitates native grasses in grasslands invaded by C. maculosa, and this facilitation can be correlated with the presence of oxalate in soil. Addition of exogenous oxalate to native grasses and Arabidopsis thaliana (L.) Heynh grown in vitro alleviated the phytotoxic effects of catechin, supporting the field experiments and suggesting that root-secreted oxalate may also act as a chemical facilitator for plant species that do not secrete the compound.     

Role of polyamines in the ontogeny of plants and their biotechnological applications

Recent developments in the metabolism and function of polyamines in plants is presented. Polyamines appear to be involved in a wide range of plant processes, however their exact role is not completely understood. In this review, the metabolic pathways involved in polyamine biosynthesis and degradation are explained, along with the transport and conjugation of these compounds. The studies involved in the understanding of function(s) of polyamines using metabolic inhibitors, as well as genetic and molecular approaches are described. Polyamine metabolism and profound changes in polyamine titres in response to infection by pathogens has been presented. Its role in adaptation of plants to stress is also presented. Molecular understanding of polyamines and their modulation in transgenics is also discussed. Further line of work in the understanding of the role of polyamines has also been focussed.     

Structure-function relationships of the RNA-dependent RNA polymerase from poliovirus (3Dpol). A surface of the primary oligomerization domain functions in capsid precursor processing and VPg uridylylation

The primary oligomerization domain of poliovirus polymerase, 3Dpol, is stabilized by the interaction of the back of the thumb subdomain of one molecule with the back of the palm subdomain of a second molecule, thus permitting the head-to-tail assembly of 3Dpol monomers into long fibers. The interaction of Arg-455 and Arg-456 of the thumb with Asp-339, Ser-341, and Asp-349 of the palm is key to the stability of this interface. We show that mutations predicted to completely disrupt this interface do not produce equivalent growth phenotypes. Virus encoding a polymerase with changes of both residues of the thumb to alanine is not viable; however, virus encoding a polymerase with changes of all three residues of the palm to alanine is viable. Biochemical analysis of 3Dpol derivatives containing the thumb or palm substitutions revealed that these derivatives are both incapable of forming long fibers, suggesting that polymerase fibers are not essential for virus viability. The RNA binding activity, polymerase activity, and thermal stability of these derivatives were equivalent to that of the wild-type enzyme. The two significant differences observed for the thumb mutant were a modest reduction in the ability of the altered 3CD proteinase to process the VP0/VP3 capsid precursor and a substantial reduction in the ability of the altered 3Dpol to catalyze oriI-templated uridylylation of VPg. The defect to uridylylation was a result of the inability of 3CD to stimulate this reaction. Because 3C alone can substitute for 3CD in this reaction, we conclude that the lethal replication phenotype associated with the thumb mutant is caused, in part, by the disruption of an interaction between the back of the thumb of 3Dpol and some undefined domain of 3C. We speculate that this interaction may also be critical for assembly of other complexes required for poliovirus genome replication.     

Exudation of fluorescent beta-carbolines from Oxalis tuberosa L roots

Root fluorescence is a phenomenon in which roots of seedlings fluoresce when irradiated with ultraviolet (UV) light. Soybean (Glycine max) and rye grass (Elymus glaucus) are the only plant species that have been reported to exhibit this occurrence in germinating seedling roots. The trait has been useful as a marker in genetic, tissue culture and diversity studies, and has facilitated selection of plants for breeding purposes. However, the biological significance of this occurrence in plants and other organisms is unknown. Here we report that the Andean tuber crop species Oxalis tuberosa, known as oca in the highlands of South America, secretes a fluorescent compound as part of its root exudates. The main fluorescent compounds were characterized as harmine (7-methoxy-1-methyl-beta-carboline) and harmaline (3, 4-dihydroharmine). We also detected endogenous root fluorescence in other plant species, including Arabidopsis thaliana and Phytolacca americana, a possible indication that this phenomenon is widespread within the plant kingdom.     

Fine needle aspiration cytology of bursal cyst

OBJECTIVE: To evaluate the cytomorphology of bursal cyst and assess the efficacy of aspiration cytology in its diagnosis and treatment. STUDY DESIGN: Nineteen cases of bursal cyst seen over four years were studied. Material was obtained by fine needle aspiration. The smears were stained with May-Grünwald-Giemsa stain and hematoxylin and eosin. RESULTS: Eight cysts were in the popliteal fossa, 4 on the elbow, 3 on the knee, 2 on the shoulder and 2 in the calf. Gelatinous material was aspirated in all the cases. In some cases the cyst collapsed after aspiration. The key diagnostic features were hypocellular smears in a mucoid background. Histiocytelike (synovial) cells were seen lying in all cases and as pseudopapillary structures in two. CONCLUSION: The presence of a cyst at a classic location with aspiration of gelatinous material and the presence of singly occurring histiocytelike cells in a mucoid background in smears is diagnostic of bursal cyst. The procedure is therapeutic in some cases.