Serena Russi

Comparison between some effects of fusicoccin and indole-3-acetic acid on cell enlargement in various plant materials

Abstract The activity of fusicoccin in stimulating water uptake in various plant tissues was investigated and compared with that of indole-3-acetic acid. In leaf disks (tomato, clover, tobacco) fusicoccin induced a significant increase of water uptake, but indole-3-acetic acid was inactive. The stimulation of water uptake by fusicoccin occurs in spite of the fact that the osmotic pressure values of the treated tissues become during incubation progressively lower than those found in the controls. This is interpreted as indirect evidence in favour of a capacity of fusicoccin to irreversibly extend the cell wall. Experiments on roots of wheat, corn and oats indicate that fusicoccin lacks, or shows in a very low degree, the typical ability of auxins to inhibit cell elongation in root tissues. The stimulation of water uptake in pea stem sections is accompanied by an irreversible extension of the cell wall. The effects of fusicoccin and indole-3-acetic acid on the increase in fresh weight and elongation of pea segments are very similar. The optimal effect of fusicoccin on the growth of pea stem segments is consistently higher than that of indole-3-acetic acid and no inhibitory effect was detected even at the highest concentration used (1·5 × 10−4 m ).

Effects of fusicoccin and some related compounds on etiolated pea tissues

Abstract At a concentration of 1 μg/ml fusicoccin and a number of closely related derivatives stimulate water uptake in cuttings of etiolated pea seedlings. It has been observed that hydrogenation or removal of the t -pentenyl group, as well as partial or total deacetylation of fusicoccin, dihydrofusicoccin, and de- t -pentenylfusicoccin give compounds which show an activity comparable to that of the parent compound. The glucose moiety appears to be necessary for high activity, but the deacetylaglycone is still capable of exerting an effect identical to that of fusicoccin when tested at 10 μg/ml. Acetylation products of fusicoccin and other active derivatives do not stimulate water uptake. Curvature of the apical segment of pea seedlings, repeatedly observed with fusicoccin, prompted a study on isolated internodes of pea seedlings. The phytotoxin produced a pronounced increase of their wet weight and elongation, as well as a definite enhancement of tissue deformability.

The isolation of trehalose and polyols from the conidia of Penicillium chrysogenum thom

Abstract Trehalose, d -mannitol, d -arabitol, meso -erythritol, and glycerol were isolated from the conidia of Penicillium chrysogenum and were quantitatively assayed. Their possible mode of formation and role during germination are discussed.

Chromatographic fractionation and chemical characterization of some oligosaccharides synthesized from lactose by Penicillium chrysogenum thom

Abstract Fractionation by column chromatography on charcoal-celite of β-galactosyl-oligosaccharides produced from lactose by Penicillium chrysogenum has shown that most of the sugars synthesized by cell-free extracts are also present in culture filtrates of the mould grown on lactose-containing media. These represent a suitabl source for the isolation of oligosaccharides in amounts large enough for the study of their chemical structure. The characterization of 3-O-β- d -galactopyranosyl- d -glucose, 6-O-β- d -galactopyranosyl- d -glucose, 6-O-β- d -galactopyranosyl- d -galactose, O-β- d -galactopyranosyl-( i →6)-O-β- d - galactopyranosyl-( i →4)- d -glucose, as well as the probable structures of two oligosaccharides containing fructose and galactose are described.

An operon for histidine biosynthesis in Streptomyces coelicolor

SummaryOn the assumption that a cluster of five his genes (eight cistrons) in S. coelicolor corresponds to an operon, a genetic analysis of a constitutive mutant was carried out. This strain has a multi-site mutation localized at the (conventional) right end of the his cluster and is derepressed for at least two enzymes coded by genes of the cluster. The study of suitable heterozygous clones (heteroclones), showed the mutation to be cis-dominant, suggesting that the operator region is affected. Most likely the strain has a deletion connecting the his operon to an adjacent amm (ammonium requirement) operon as demonstrated by its inability to utilize nitrate as nitrogen source and to complement or recombine with two his cistrons and a near-by amm mutation.