The initial rate of (2-(14)C)acetic acid (AA) uptake by corn roots was used for probing the dependency of the root cell surface pH on H(+) excretion. AA influx was linearly related to AA concentration, dependent on the concentration of the undissociated form (AH), unaffected by variations of the membrane potential, and was thus assumed to result mainly from the free diffusion of AH across the m...

We have recently reported on the purification of the fusicoccin (FC) receptor from corn (Zea mays L.) and its identification by photoaffinity labeling (P. Aducci, A. Ballio, V. Fogliano, M.R. Fullone, M. Marra, N. Proietti [1993] Eur J Biochem 214: 339-345). Pure preparations of FC receptors, obtained under nondenaturing conditions, showed in sodium dodecyl sulfate-polyacrylamide gel electropho...

The effect of the purified host-selective toxin victorin C, a cyclized penta peptide, was compared to that of CCCP and vanadate on membrane functions of susceptible leaves, roots, and single root cap cells of Avena sativa with conventional electrophysiology. The plasmalemma depolarized irreversibly by about 80 millivolts and to below the diffusion potential within 1 hour. Concentrations as low ...

Phloem tissue isolated from celery (Apium graveolens L.) was used to investigate the regulation of sucrose uptake by turgor (manipulated by 50-400 milliosomolal solutions of polyethylene glycol) and hormones indoleacetic acid (IAA) and gibberillic acid (GA(3)). Sucrose uptake was enhanced under low cellular turgor (increase in the V(max)). Furthermore, enhancement of sucrose uptake was due to a...

The NFX1-LIKE1 (NFXL1) and NFXL2 genes were identified as regulators of salt stress responses. The NFXL1 protein is a nuclear factor that positively affects adaptation to salt stress. The nfxl1-1 loss-of-function mutant displayed reduced survival rates under salt and high light stress. In contrast, the nfxl2-1 mutant, defective in the NFXL2 gene, and NFXL2-antisense plants exhibited enhanced su...

The investigations were focussed on the question as to whether roots of intact maize plants (Zea mays L. cv Blizzard) release protons into deionized H(2)O. Plants in the six to seven leaf stage depressed the pH of deionized H(2)O from 6 to about 4.8 during an experimental period of 4 hours. Only one-third of the protons released could be ascribed to the solvation of CO(2) in H(2)O. The main cou...

Outbreaks of salmonellosis related to consumption of fresh produce have raised interest in Salmonella-plant interactions leading to plant colonization. Incubation of gfp-tagged Salmonella enterica with iceberg lettuce leaves in the light resulted in aggregation of bacteria near open stomata and invasion into the inner leaf tissue. In contrast, incubation in the dark resulted in a scattered atta...

A four- to seven-fold enhancement of leaf hydraulic conductance by light has been reported in three temperate tree species. The enhancement occurs in the liquid-flow pathway between the petiole and the site of water evaporation. The enhancement occurs within 1 h, and dissipates in darkness over a period of 1 to 10 h depending on species. Here we report light-induced enhancement of leaf hydrauli...

Many clinically useful pharmaceuticals are semi-synthesized from natural products produced by actinobacteria and fungi. The synthetic protocols usually contain many complicated reaction steps and thereby result in low yields and high costs. It is therefore important to breed microorganisms that produce a compound most suitable for chemical synthesis. For a long time, desirable mutants have been...

In isolated phloem segments of celery (Apium graveolens L.), a tissue highly specific for sucrose and mannitol uptake, glucose uptake occurs at very low rates and exhibits biphasic kinetics. Nonpenetrating inhibitors such as parachloromercuribenzene sulfonic acid did not inhibit glucose uptake. However, uptake was greatly inhibited by penetrating inhibitors such as N-ethylmaleimide and carbonyl...