Ulrike Noll

Lignin biosynthetic enzymes in stem rust infected, resistant and susceptible near-isogenic wheat lines☆

Abstract Near-isogenic lines of the wheat cultivar Prelude, carrying either the Sr5 gene for resistance or the sr5 allele for susceptibility were inoculated with the stem rust fungus Puccinia graminis f. sp. tritici race 32, which possesses the P5 gene for avirulence. The time-course of the enzyme activities of the general phenylpropanoid pathway, phenylalanine ammonia-lyase (PAL) and 4-coumarate:CoA ligase (4CL), as well as the enzyme activities of the specific pathway leading to the biosynthesis of lignin, cinnamyl-alcohol dehydrogenase (CAD) and peroxidase (PO), were determined. The resistant and the susceptible isoline both exhibit a first maximum in the coordinately regulated enzyme activities of PAL and 4CL at a time when the fungus is still growing on the surface of the leaves. This maximum is followed by a decrease to the levels of uninoculated controls. In the resistant isoline, a second increase is observed at the time of the hypersensitive resistant reaction. In contrast, enzyme activities in susceptible plants continue to decline, even falling below control levels until the onset of sporulation when a second, late increase can be detected. The observed changes in CAD and PO activities are consistent with a feed-forward regulation by products of the general phenylpropanoid pathway. However, no late increase in PO activity can be observed in the compatible interaction. An interpretation of these results is proposed in terms of non-host resistance, basic compatibility and race-cultivar specific resistance.

A wheat cell wall fragment suppresses elicitor-induced resistance responses and disturbs fungal development.

Summary A fraction prepared by Pectolyase-digestion of wheat cell walls suppressed plant responses when co-injected with a fungal elicitor of hypersensitive-like lignification.This fraction also reduced haustorial mother cell formation and prevented the development of haustoria when injected into wheat leaves prior to inoculation with the stem rust fungus.

Fructose-2,6-Bisphosphate in Wheat Leaves Infected with Stem Rust

Summary Fructose-2,6-bisphosphate (Fru-2,6-P 2 ) is a potent cytosolic regulatory molecule of carbohydratepartitioning in plants. Seven-day-old plants of three near-isogenic wheat lines ( Triticum aestivum cv. Prelude), carrying either solely genes for susceptibility, the Sr24 -allele for moderate resistance, or the Sr5 -allele for high resistance, were inoculated with race 32 of the stem rust fungus ( Puccinia graminis f. sp. tritici P5 /P24). The Fru-2,6-P 2 content of primary leaves was measured over a period of 9 days after infection. In non-inoculated control samples of all isolines, the Fru-2,6-P 2 level rose up to 2- to 5-fold until the 7thday after infection as compared to initial values. In susceptible plants, this increase was completely stopped 4 to 5 days after infection, i.e. at the time sporulation began. In contrast, no infection-related effect on the Fru-2,6-P2 content was observed in the highly resistant isoline, whereas moderately resistant plants transiently exhibited higher values in infected relative to healthy leaves 3 to 5 days after inoculation. These results are discussed on the basis of the known functions of Fru-2,6-P 2 in photosynthetically active plant tissues.

The defense substance allicin from garlic permeabilizes membranes of Beta vulgaris, Rhoeo discolor, Chara corallina and artificial lipid bilayers

BACKGROUND Allicin (diallylthiosulfinate) is the major volatile- and antimicrobial substance produced by garlic cells upon wounding. We tested the hypothesis that allicin affects membrane function and investigated 1) betanine pigment leakage from beetroot (Beta vulgaris) tissue, 2) the semipermeability of the vacuolar membrane of Rhoeo discolor cells, 3) the electrophysiology of plasmalemma and tonoplast of Chara corallina and 4) electrical conductivity of artificial lipid bilayers. METHODS Garlic juice and chemically synthesized allicin were used and betanine loss into the medium was monitored spectrophotometrically. Rhoeo cells were studied microscopically and Chara- and artificial membranes were patch clamped. RESULTS Beet cell membranes were approximately 200-fold more sensitive to allicin on a mol-for-mol basis than to dimethyl sulfoxide (DMSO) and approximately 400-fold more sensitive to allicin than to ethanol. Allicin-treated Rhoeo discolor cells lost the ability to plasmolyse in an osmoticum, confirming that their membranes had lost semipermeability after allicin treatment. Furthermore, allicin and garlic juice diluted in artificial pond water caused an immediate strong depolarization, and a decrease in membrane resistance at the plasmalemma of Chara, and caused pore formation in the tonoplast and artificial lipid bilayers. CONCLUSIONS Allicin increases the permeability of membranes. GENERAL SIGNIFICANCE Since garlic is a common foodstuff the physiological effects of its constituents are important. Allicins ability to permeabilize cell membranes may contribute to its antimicrobial activity independently of its activity as a thiol reagent.

Influence of different safety shoes on gait and plantar pressure: a standardized examination of workers in the automotive industry

Working conditions, such as walking and standing on hard surfaces, can increase the development of musculoskeletal complaints. At the interface between flooring and musculoskeletal system, safety shoes may play an important role in the well‐being of employees. The aim of this study was to evaluate the effects of different safety shoes on gait and plantar pressure distributions on industrial flooring.