Complex relation between triazine-susceptible phenotype and genotype in the weed Senecio vulgaris may be caused by chloroplast DNA polymorphism

The weed Senecio vulgaris acquired high levels of resistance to triazine herbicides soon after the latter’s introduction. As in most weeds, triazine resistance is conferred by a point mutation in the chloroplast psbA gene that negatively affects the fitness of its carrier. To assess levels of triazine resistance in S. vulgaris field populations, we adopted a PCR-RFLP-based molecular diagnostic test recently developed for the triazine resistance-conferring region of the psbA gene of other weeds, including Brassica napus, Chenopodium spp. and Amaranthus spp., and compared these molecular results to the phenotypic response after triazine application. A highly significant linear correlation was found between phytotoxic symptoms and biomass reduction. Variability in phenotypic response was not only found between populations or inbred lines of S. vulgaris but also within replicates of the same inbred line. No clear relationship, however, was found between the DNA restriction pattern and the phenotypic response to triazine application, thereby throwing doubt on the use of such molecular diagnostic tests to track triazine resistance in S. vulgaris. Our results indicate that the chloroplast genome of S. vulgaris is polymorphic and that the level of polymorphism may be variable within single leaves of individual plants. We discuss the possible genetic basis of this polymorphism and its consequence for the acquisition and inheritance of chloroplast-based traits. Received: 28 December 1998 / Accepted: 20 February 1999     

Relative importance of osmotic-stress and ion-specific effects on ABA-mediated inhibition of leaf expansion growth in Phaseolus vulgaris

The osmotic and ion-specific components of salt-induced inhibition of leaf expansion growth were investigated in beans grown from 12 h to several days in either NaCl-containing solution cultures, an isosmotic concentrated macronutrient solution, or a vermiculite–compost mixture with low Na⁺ but high Cl^– availability. Inhibition of leaf expansion and leaf ABA increase was more intense in the NaCl than in the isosmotic macronutrient treatment. Root Na⁺ was highly correlated to inhibition of leaf expansion and leaf or xylem sap ABA. When Na⁺ was sequestered in soil, salinized plants showed no reduction in leaf expansion or ABA increase, regardless of the presence of high leaf Cl^– concentrations. Stomatal conductance exhibited an exponential relationship with the reciprocal value of xylem sap ABA. Our results indicate that an ion-specific effect caused by Na⁺ in roots may account for an ABA-mediated reponse of both stomatal closure and leaf expansion inhibition.     

EFFECTS OF ARSENATE ON GROWTH OF NITROGEN-AND PHOSPHORUS-LIMITED CHLORELLA VULGARIS (CHLOROPHYCEAE) ISOLATES1

The effects of arsenate on the growth characteristics of five isolates of the freshwater alga, Chlorella vulgaris Beij., were examined. Two field isolates originated from arsenic-contaminated sites in Yukon, Canada and Kyushi, Japan; two reference isolates were obtained from the University of Texas Culture Collection. One isolate was selected for arsenic-tolerance in the laboratory. All five strains survived in culture solutions containing high arsenate concentrations. Arsenate (1–25 mM As) reduced photosynthesis and cell growth, as reflected by induced lag periods, slower growth rates, and lower stationary cell yields. Field isolates had shorter lag periods, higher growth rates, and enhanced cell yields compared to lab isolates when exposed to the same arsenic concentrations. Growth of the phosphorus-limited field strains was stimulated by the addition of arsenic. The cell yield of phosphorus-limited C. vulgaris Yukon, when treated with arsenic, was two times that of the phosphorus-limited control. This pattern was not evident when photosynthesis was used as a measure of cell response.     

Directed mutagenesis confirms the functional importance of positively selected sites in polygalacturonase inhibitor protein

Polygalacturonase inhibitor proteins (PGIPs) protect plants against invasion by diverse microbial and invertebrate enemies that use polygalacturonase (PG) to breach the plant cell wall. Directed mutagenesis has identified specific natural mutations conferring novel defensive capability in green bean PGIP against a specific fungal PG. These same sites are identified as positively selected by phylogenetic codon-substitution models, demonstrating the utility of such models for connecting retrospective comparative analyses with contemporary, ecologically relevant variation.     

Disturbed nitrogen metabolism associated with the hyperhydric status of fully habituated callus of sugarbeet

The content of polyamines and proline was much lower in a normal (N) callus of Beta vulgaris L. than in a fully habituated hyperhydric (H) callus. The H callus also contained more glutamate and had a higher glutamate dehydrogenase activity. The excess of glutamate, in this chlorophyll-deficient callus, was linked to accumulation of proline and polyamines. Experiments with α-difluoromethylornithine (DFMO) and α-difluoromethylarginine (DFMA) showed that both ornithine decarboxylase and arginine decarboxylase participated in the synthesis of polyamines (especially spermidine and putrescine) and removal of ammonia. It is hypothesized that the H callus was subjected to ammonia stress from the start of the culture. Experiments with gabaculine, an inhibitor of ornithine aminotransferase, showed that this enzyme linked proline degradation to polyamine synthesis through the production of ornithine. This disturbed nitrogen metabolism appeared to be characteristic of the fully habituated callus and might explain the low growth of this hyperhydric tissue.     

Initial Stages of Morphogenetic Changes in Detached Cotyledons,Hypocotyls, and Leaves of Kidney Beans and Eggplants under Salinity Conditions

The effects of salinity on the morphogenesis of various organs of kidney bean (Phaseolus vulgaris L.) and eggplant (Solanum melongena L.) plants grown in nosterile culture and of explants from these organs grown in vitro were studied. Salt stress was produced by adding NaCl (0.5 and 1.0%) to water or the Murashige and Skoog nutrient medium. Salt stress suppressed rhizogenesis, particularly profoundly in the salt-sensitive beans. Callus cultures obtained from different organs differed in their salt tolerance, which was evaluated from the callus growth. Under salinity conditions, homologous structures of the two crops differed markedly in survival and regeneration. Different organs and corresponding explants of one and the same plant differed in the threshold sensitivity to salinity, which indicates the organ-specificity of salt resistance.     

K14、K19在寻常型银屑病发病中的作用机制研究

目的:研究细胞角蛋白K14、K19在寻常型银屑病(PV)发病中的作用机制。方法:选择从2012年1月到2016年12月在西安交通大学第二附属医院皮肤科就诊的PV患者60例纳入本次研究。将PV患者在皮损区及未受累皮肤区分别取1份皮肤,制成存档蜡块,分别记为PV皮损组和PV未受累皮肤组各60例。另选同期在我院接受外伤手术治疗的健康皮肤60例作为对照组,分析K14、K19在PV中的阳性表达率以及表达水平,分析K14及K19在PV皮损区阳性表达的相关性。结果:各组的K14及K19阳性表达率以及表达水平比较差异有统计学意义(P0.05)。PV皮损组和PV未受累皮肤组的K14阳性表达率及表达水平明显高于对照组,K19阳性表达率及表达水平明显低于对照组,差异有统计学意义(P0.05)。PV皮损组的K14阳性表达率及表达水平明显高于PV未受累皮肤组,K19阳性表达率及表达水平明显低于PV未受累皮肤组,差异有统计学意义(P0.05)。根据Spearman法分析相关性发现,K14及K19在PV皮损区阳性表达中呈负相关(r=-0.871,P=0.000)。结论:K14及K19均在PV发病过程中出现异常表达,其中K14阳性表达较强,而K19阳性表达较弱,二者在PV皮损区阳性表达中呈负相关。临床上可考虑监测K14及K19的阳性表达水平,从而更好地辅助临床诊断及病情的预估,值得临床医师关注与重视。     

Biosynthesis of 5-aminolevulinic Acid via the Shemin Pathway in a Green Sugar Beet Callus

5-Aminolevulinic acid synthase (ALAS) has been detected in a normal (auxin- and cytokinin-dependent) green sugar beet callus under light and under darkness. ALAS activity was lower when the callus was grown under light. The supply of precursors of the Shemin pathway (glycine and succinate) to dark-grown callus enhanced considerably the capacity of the 5-aminolevulinic acid (ALA) formation. Glutamate, -aminobutyrate or -ketoglutarate also increased ALA accumulation. Such an accumulation was also obtained after inhibition of polyamine synthesis. The results show that glutamate or its derivatives might feed the Shemin pathway in conditions preventing glutamate to be used through the Beale pathway.     

Impact of sheep grazing on nutrient budgets of dry heathlands

Questions: What effect does sheep grazing have on the nutrient budgets of heathlands? Can grazing compensate for atmospheric nutrient loads in heathland ecosystems? What are the conclusions for heathland management? Location: Lüneburg Heath, NW Germany. Methods: During a one-year grazing experiment (stocking rate 1.1 sheep/ha) nutrient balances for N, Ca, K, Mg and P were calculated by quantifying input rates (atmospheric deposition, sheep excrement) and output rates (biomass removal, leaching). Results: Atmospheric nutrient deposition amounted to 22.8 kg.ha⁻¹.a⁻¹ for N and < 0.2 kg.ha⁻¹.a⁻¹ for P. Sheep excrement increased the inputs for N and P by ca. 3.5 and 0.2 kg.ha⁻¹.a⁻¹, respectively. Grazing reduced N- and P-stores in the above-ground biomass by 25.6 and 1.9 kg.ha⁻¹.a⁻¹, respectively. N-and P-losses via leaching amounted to 2.2 and < 0.2 kg.ha⁻¹.a⁻¹. Output:input ratios for P were high, indicating that grazing severely affected P-budgets of heaths. Conclusions: Our results suggest that sheep grazing has the potential to compensate for atmospheric nutrient loads (particularly for current N deposition rates). However, in the long term the combination of elevated N-deposition and P-loss due to grazing may cause a shift from N-(co-) limited to more P-(co-) limited plant growth. To counteract an aggravation of P-deficiency in the long term, grazing may be combined with management measures that affect P-budgets to a lesser extent (e.g. prescribed burning).     

Dynamics of growth and the content of endogenous phytohormones during kidney bean scoto-and photomorphogenesis

The dynamics of growth and the contents of free and bound endogenous IAA, gibberellins (GA), cytokinins (zeatin and its riboside), and ABA in kidney bean plants (Phaseolus vulgaris L., cv. Belozernaya) grown in darkness or in the light was studied. Phytohormones were quantified in 5–15-day-old plants by the ELISA technique. Plant growth and phytohormone content were shown to depend on plant age and the conditions of illumination. During scotomorphogenesis, changes in the biomass and hypocotyl length were highly correlated with the content of GA, whereas during photomorphogeneses, these parameters were correlated with the content of zeatin. In darkness, epicotyl growth displayed a positive correlation with the content of GA, whereas in the light, the correlation was negative. Growth characteristics of the primary leaves were shown to correlate with IAA in darkness and with GA and zeatin in the light. At a low concentration of cytokinins in illuminated leaves, cell divisions occurred, whereas, at the higher cytokinin concentrations, cell expansion occurred. The highest content of GA was characteristic of leaves in the period of growth cessation. ABA accumulated during active leaf and root elongation and biomass increment in the light and during hypocotyl growth in darkness. After plant illumination, the ratio of auxins to cytokinins increased in bean roots and decreased in their epicotyls. Thus, light changed the developmental programs of bean plants, which was manifested in the changed rate and duration of growth of various organs (root, hypocotyl, epicotyl, and leaf). Some mechanisms of light action depended on the contents of IAA, ABA, GA, and cytokinins and the ratios between these phytohormones. Differences between scotonorphogenesis of mono-and dicotyledonous plants are discussed in relation to the levels of phytohormones in them.