Ploidy reduction and genome segregation in cultured carrot cell lines. I. Prophase chromosome reduction

Cytological analysis of different carrot cell lines in culture has shown various cytogenetic anomalies generating new levels of ploidy and novel chromosome numbers. Polyploidy may be considered a reservoir of variability that can be released in the form of distinct new segregants of different ploidy. Mechanisms alternative to mitosis (reductional grouping, prophase chromosome reduction) operate from a polyploid state (possibly reached by means of endopolyploidy, endomitosis, nuclear fusion, or restitution nuclei) to generate new levels of ploidy and novel chromosome numbers necessary for selection to operate in vitro. The segregational phenomena require chromosome recognition in haploid set complements and abnormal behaviour of mitoses; the resulting chromosome variability suggests that chromosomes are arranged, in the resting nuclei, in an orderly and predictable manner.The knowledge of the molecular events governing these mechanisms, and how to control them, would be of great help for future applications of plant cell culture.     

Higher alcohol and acetic acid production by apiculate wine yeasts

P. ROMANO, G. SUZZI, G. COMI AND R. ZIRONI. 1992. Ninety-six strains of apiculate wine yeasts were investigated for their ability to produce higher alcohols and acetic acid in synthetic medium. Less isoamyl alcohol and more n -propanol and isobutanol were formed by Hanseniaspora guilliermondii than by Kloeckera apiculata. The latter produced twice as much acetic acid as H. guilliermondii. The production of higher alcohols and acetic acid was found to be a characteristic of individual strains and was statistically significant. In a multivariate analysis of higher alcohol production two main groupings were formed at 86%S, corresponding to the taxa H. guilliermondii and K. apiculata. Strains that produced low amounts (50 mg/1) of acetic acid, comparable with that of Saccharomyces cerevisiae, were found in both species of apiculate yeasts.     

Age-dependent population diffusion with external constraint

We present a simple model for age dependent population diffusion when the dynamics is submitted to external constraints. Existence, uniqueness and dependence on the parameters of the solution are discussed.This work has been done within the framework of the cultural agreement between the Universities of Bordeaux and Rome     

Orientation of anosmatic pigeons

Summary Test releases performed at five symmetrically arranged sites around the loft, at a distance of 78–99 km from it, showed that 1) anosmatic birds transported without alteration of the earth's magnetic field were completely random-oriented, 2) anosmatic birds transported in a container inside which the intensity of the magnetic field was strongly reduced were unable to orientate homewards and mostly departed according to a preferred compass direction, 3) control birds, which could smell, and were transported without alteration of the magnetic field, were homeward oriented and performed better in homing than both experimental groups. The conclusion is that anosmatic birds are unable to detect home direction at unfamiliar sites and that magnetic stimuli perceived during the outward journey are unable to substitute olfactory cues.Abbreviation PCD preferred compass direction Supported by a grant from the Consiglio Nazionale delle Ricerche     

Protein-protein interaction in transport

The transport of histidine in the gram negative bacterium S. typhimurium has been studied over a number of years and found to occur through five transport systems (Ames, 1972). Of these, the one with the highest affinity has been studied in detail from the genetic, physiological and biochemical point of view. This system, known as the high-affinity histidine permease, is composed of two subsystems, the J-P and K-P systems, which have a component in common, the P protein, presumed to be membrane-bound. The J-P system, moreover, is known to require the presence of a periplasmic histidine-binding protein, the J protein. The J protein is coded for by the hisJ gene and the P protein is coded for by the hisP gene. Both of these genes have been mapped at 75 min on the Salmonella chromosomal map. Adjacent to them is a regulatory gene, the dhuA gene. The periplasmic histidine-binding protein J has been shown to interact directly with the second component of transport, the P protein (Ames and Spudich, 1976). In accordance with this, histidine-binding protein J has been shown to contain, besides the histidine-binding site, a second site, essential for function, the interaction site (Kustu and Ames, 1974). We have recently shown that a mutant J protein with a defective interaction site but an intact histidine-binding site cannot function in histidine transport, unless an appropriate compensating mutation is introduced in the P protein. The interaction between the J and P proteins is an obligatory step in transport. The mutation in the interaction site of the J protein has been shown to map in the hisJ gene, and the compensating supressor mutation in the P protein has been shown to map in the hisP gene. Our contention that the J and P proteins engage in a functional interaction assumes further strength from other studies on protein-protein interaction in bacteriophage development and in ribosomal structure. Among the possible functions of the J-P interaction in histidine transport, a likely one is the transmission of information to the P protein, concerning whether or not the histidine-binding site on the J protein is occupied. Appropriate conformational changes then can occur in either the J or the P protein, or both, such that the histidine is released in the correct location and direction on the inside of the cell. This could occur either by a pore-formation mechanism or by binding-site translocation. Another alternative is that the P protein is part of an energy transducing mechanism in which energy is transmitted to the J protein, through the interaction site, as a prerequisite for the J protein participation in translocation. Among the interesting findings coming out of this work, is also the fact that the P protein performs a central function in transport being involved in the permeation of other substrates besides histidine. It is likely that other binding proteins besides the J protein require the P protein. Thus an interesting question which we are trying to answer at present is whether the P protein has separate interaction sites for each of these other binding proteins requiring its function, or whether they all interact at one common site.     

Ethanol production potential of sweet sorghum assessed using forage fiber analysis procedures

Sweet sorghum (Sorghum bicolor (L.) Moench) is widely recognized as a highly promising biomass energy crop with particular potential to complement sugarcane production in diversified cropping systems. Agronomic assessments have led to identification of four cultivars well suited for such sugarcane‐based production systems in southern Louisiana. Sweet sorghum biofuel production systems are currently being developed, and research producing large sample numbers requiring ethanol yield assessment is anticipated. Fiber analysis approaches developed for forage evaluation appear to be useful for screening such large numbers of samples for relative ethanol yield. Chemical composition, forage fiber characteristics, digestibility, and ethanol production of sweet sorghum bagasse from the four cultivars were assessed. Measures of detergent fiber, lignin, and digestibility were highly correlated with ethanol production (P < 0.01). The best linear regression models accounted for about 80% of the variation among cultivars in ethanol production. Bagasse from the cultivar Dale produced more ethanol per gram of material than any of the other cultivars. This superior ethanol production was apparently associated with less lignin in stems of Dale. Forage evaluation measures including detergent fiber analyses, in vitro digestibility, and an in vitro gas production technique successfully identified the cultivar superior in ethanol yield indicating their usefulness for screening sweet sorghum samples for potential ethanol production in research programs generating large sample numbers from evaluations of germ plasm or agronomic treatments. These screening procedures reduce time and expense of alternatives such as hexose sugar assessment for calculating theoretical ethanol yield.