Chromatin modification acts as a memory for systemic acquired resistance in the plant stress response

Priming of defence genes for amplified response to secondary stress can be induced by application of the plant hormone salicylic acid or its synthetic analogue acibenzolar S‐methyl. In this study, we show that treatment with acibenzolar S‐methyl or pathogen infection of distal leaves induce chromatin modifications on defence gene promoters that are normally found on active genes, although the genes remain inactive. This is associated with an amplified gene response on challenge exposure to stress. Mutant analyses reveal a tight correlation between histone modification patterns and gene priming. The data suggest a histone memory for information storage in the plant stress response.     

Rat Mesentery Angiogenesis Assay

The adult rat mesentery window angiogenesis assay is biologically appropriate and is exceptionally well suited to the study of sprouting angiogenesis in vivo [see review papers], which is the dominating form of angiogenesis in human tumors and non-tumor tissues, as discussed in invited review papers^1,2. Angiogenesis induced in the membranous mesenteric parts by intraperitoneal (i.p.) injection of a pro-angiogenic factor can be modulated by subcutaneous (s.c.), intravenous (i.v.) or oral (p.o.) treatment with modifying agents of choice. Each membranous part of the mesentery is translucent and framed by fatty tissue, giving it a window-like appearance.The assay has the following advantageous features: (i) the test tissue is natively vascularized, albeit sparsely, and since it is extremely thin, the microvessel network is virtually two-dimensional, which allows the entire network to be assessed microscopically in situ; (ii) in adult rats the test tissue lacks significant physiologic angiogenesis, which characterizes most normal adult mammalian tissues; the degree of native vascularization is, however, correlated with age, as discussed in¹; (iii) the negligible level of trauma-induced angiogenesis ensures high sensitivity; (iv) the assay replicates the clinical situation, as the angiogenesis-modulating test drugs are administered systemically and the responses observed reflect the net effect of all the metabolic, cellular, and molecular alterations induced by the treatment; (v) the assay allows assessments of objective, quantitative, unbiased variables of microvascular spatial extension, density, and network pattern formation, as well as of capillary sprouting, thereby enabling robust statistical analyses of the dose-effect and molecular structure-activity relationships; and (vi) the assay reveals with high sensitivity the toxic or harmful effects of treatments in terms of decreased rate of physiologic body-weight gain, as adult rats grow robustly.Mast-cell-mediated angiogenesis was first demonstrated using this assay^3,4. The model demonstrates a high level of discrimination regarding dosage-effect relationships and the measured effects of systemically administered chemically or functionally closely related drugs and proteins, including: (i) low-dosage, metronomically administered standard chemotherapeutics that yield diverse, drug-specific effects (i.e., angiogenesis-suppressive, neutral or angiogenesis-stimulating activities⁵); (ii) natural iron-unsaturated human lactoferrin, which stimulates VEGF-A-mediated angiogenesis⁶, and natural iron-unsaturated bovine lactoferrin, which inhibits VEGF-A-mediated angiogenesis⁷; and (iii) low-molecular-weight heparin fractions produced by various means^8,9. Moreover, the assay is highly suited to studies of the combined effects on angiogenesis of agents that are administered systemically in a concurrent or sequential fashion.The idea of making this video originated from the late Dr. Judah Folkman when he visited our laboratory and witnessed the methodology being demonstrated.Review papers (invited) discussing and appraising the assayNorrby, K. In vivo models of angiogenesis. J. Cell. Mol. Med. 10, 588-612 (2006).Norrby, K. Drug testing with angiogenesis models. Expert Opin. Drug. Discov. 3, 533-549 (2008).     

Growth responses and fitness costs after induction of pathogen resistance depend on environmental conditions

Fitness costs of resistance are among the most widely discussed explanations for the evolution of induced resistance, but studies on induced resistance to pathogens are scarce and contradictory. In the present study the influence of nitrogen supply, length of the growing period and competition on the seed production of Arabidopsis in response to treatment with the chemical resistance elicitor BION^® was investigated. BION^® treatment elicited resistance to the bacterial pathogen Pseudomonas syringae, and biochemical changes after BION^® treatment were similar to those observed after bacterial infection. Induced plants grew more slowly during the first week after resistance induction, for which they then compensated by exhibiting faster growth than controls. Whether or not induced plants produced less seeds than controls depended on growing conditions. Costs, no costs and even higher seed production by induced plants were observed in experiments differently combining abiotic conditions. A higher seed production by induced plants arose particularly when the vegetation period was short, most probably a consequence of senescence-related processes that had been activated by resistance elicitation. Induced plants, however, produced less seeds when competing with controls and experiencing a full growing period. Studies controlling only some of the critical environmental factors can easily lead to apparently contradictory results, which in fact represent different outcomes of a complex interplay of factors.     

Peroxidase isozyme analysis of factors involved in development of symptoms in Nicotiana clevelandii infected by plum pox virus

Isozyme profiles of peroxidases (POX, EC 1.11.1.7) have been determined in leaves at different developmental stages as well as in other tissues of Nicotiana clevelandii . Modifications of the POX profiles associated with infection by plum pox virus and their relationship to senescence and wounding have also been determined. Systemically infected leaves displaying symptoms of infection showed a pattern highly similar to that of old leaves. Extensive alterations in the POX profile were observed in the inoculated leaves, and both ageing and wounding seemed to contribute to these transformations. The isozyme profile of POX after ethrel treatments suggested that ethylene could be involved in the senescence reaction produced by the virus infection.     

Jasmonic Acid and Salicylic Acid Induce Accumulation of β-1,3-Glucanase and Thaumatin-Like Proteins in Wheat and Enhance Resistance Against Stagonospora nodorum

The effect of application of jasmonic acid (JA) and salicylic acid (SA) on the induction of resistance in wheat to Stagonospora nodorum and on the induction of -1,3-glucanase and thaumatin-like proteins (TLPs) was studied. Western blot analysis revealed that two -1,3-glucanases with apparent molecular masses of 31 and 33 kDa that cross-reacted with a barley glucanase antiserum were induced in wheat leaves after treatment with JA and SA. When wheat plants were treated with SA and JA, a TLP with an apparent molecular mass of 25 kDa and several other isoforms of TLP were induced. Pre-treatment of wheat plants with SA and JA significantly reduced (up to 56 %) the incidence of leaf blotch disease incited by S. nodorum compared with untreated control plants.     

The IL-6 promoter polymorphism is associated with disease activity and disability in systemic sclerosis

Systemic sclerosis (SSc) is a rare, autoimmune disease characterized by cutaneous and visceral fibrosis. Interleukin- 6 (IL-6) is involved in the pathogenesis of many immune-mediated diseases. IL-6 plays an important role in the initiation and promotion of fibrosis. The polymorphism in the position -174 (G/C) of the promoter region of the IL-6 gene (IL-6pr) may alter the expression of the gene. Complete linkage disequilibrium was observed between the -174 and -597 alleles. The aim of this study is to investigate the possible influence of -597 (-174) IL-6pr polymorphism on the susceptibility and/or the clinical course of SSc in Romanian population. Genotyping of -597 variant was performed by an RFLP method on 20 SSc patients and 26 healthy subjects. Patients having the homozygous GG (-597) genotype had higher disease activity and disability scores than heterozygous GA patients: the European Scleroderma Study Group (EScSG) disease activity score was 5.0 +/- 3.3 in homozygous GG subjects vs. 2.4 +/- 3.6 in heterozygous GA patients (p < 0.05), and the Disability Index of the Health Assessment Questionnaire (HAQ-DI) was 1.42 +/- 1.04 in homozygous GG subjects vs. 0.53 +/- 0.55 in heterozygous GA patients (p < 0.05). No difference was observed in the distribution of allele frequencies between SSc patients and healthy controls. Conclusions: The GG homozygosis was found to be associated with a higher degree of illness activity and disability in SSc patients. No statistically significant differences were found between SSc patients and healthy controls with respect to the -597 allele distribution.     

Oral health and morbidity--implications of oral infections on the elderly

Detrimental effects of oral infections on general health have been known for almost 3000 years. Modern studies, however, have cast new light on the pathogenic mechanisms by which oral infections appear to link with morbidity and mortality. In particular, among the elderly, poor dental health seems to associate with all-cause mortality. This review aims to provide an overview of present knowledge of these issues, starting from dental bacteraemia, oral mucosal infections and problems of drug resistance and, briefly, discussing what is known about the link between oral health and some systemic diseases such as atherosclerosis and type-2 diabetes. The main conclusions are that scientific evidence is still weak on these interactions and that the elderly should be better taken into account when planning future studies. Functions of the body differ in the frail and diseased from those of the young. Consequently, novel prevention and treatment strategies should be developed and properly tested for combating oral infections in elderly populations. Specific suggestions for further research are outlined.     

Xylem structure and connectivity in grapevine (Vitis vinifera) shoots provides a passive mechanism for the spread of bacteria in grape plants

BACKGROUND AND AIMS: Bacterial leaf scorch occurring in a number of economically important plants is caused by the xylem-limited bacterium Xylella fastidiosa (Xf). In grapevine, Xf systemic infection causes Pierce's disease and is lethal. Traditional dogma is that Xf movement between vessels requires the digestion of inter-vessel pit membranes. However, Yersinia enterocolitica (Ye) (a bacterium found in animals) and fluorescent beads moved rapidly within grapevine xylem from stem into leaf lamina, suggesting open conduits consisting of long, branched xylem vessels for passive movement. This study builds on and expands previous observations on the nature of these conduits and how they affect Xf movement. METHODS: Air, latex paint and green fluorescence protein (GFP)-Xf were loaded into leaves and followed to confirm and identify these conduits. Leaf xylem anatomy was studied to determine the basis for the free and sometimes restricted movement of Ye, beads, air, paint and GFP-Xf into the lamina. KEY RESULTS: Reverse loading experiments demonstrated that long, branched xylem vessels occurred exclusively in primary xylem. They were observed in the stem for three internodes before diverging into mature leaves. However, this stem-leaf connection was an age-dependent character and was absent for the first 10-12 leaves basal to the apical meristem. Free movement in leaf blade xylem was cell-type specific with vessels facilitating movement in the body of the blade and tracheids near the leaf margin. Air, latex paint and GFP-Xf all moved about 50-60% of the leaf length. GFP-Xf was never observed close to the leaf margin. CONCLUSIONS: The open vessels of the primary xylem offered unimpeded long distance pathways bridging stem to leaves, possibly facilitating the spread of bacterial pathogens in planta. GFP-Xf never reached the leaf margins where scorching appeared, suggesting a signal targeting specific cells or a toxic build-up at hydathodes.