Identification of Metabolic Pathways Expressed by Pichia anomala KH6 in the Presence of the Pathogen Botrytis cinerea on Apple: New Possible Targets for Biocontrol Improvement

peer reviewe

Evaluation of two protein extraction protocols for Pichia anomala proteome analysis.

Pichia anomala (strain Kh6) was isolated from the surface of apple fruits and selected for its high and reliable biocontrol activity against Botrytis cinerea and Penicillium expansum. Its main modes of action have until now been studied using essentially microbiological and molecular approaches. The study continues now using the proteomic approach and considering the in situ P. anomala/B. cinerea/apple interaction. Two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) is one of the most powerful tools used for proteomic analysis. It combines two sequential separation steps, the first dimension via isoelectric focusing (IEF) and the second one by SDS PAGE. Although recent advances in 2-D PAGE, the extraction of the whole proteome and the removal of interfering contaminants still limit its application. Sample preparation constitutes indeed a critical influential step for IEF which in turn affects 2-D gel quality. The objective of the present work was thus to develop an effective protein extraction protocol designed for 2-D PAGE analysis of the proteome of P. anomala strain Kh6. As a starting point, two contrasting protein extraction protocols were chosen to be evaluated in terms of protein yield and one-dimensional (1-D) SDS PAGE and 2-D PAGE gel patterns. The first protocol uses a urea/thiourea-based lysis buffer whereas the second protocol utilizes a hot SDS-based lysis buffer with an additional precipitation step. The comparison model used consisted of apples treated with strain Kh6 alone (K) and apples first treated with Kh6 and then inoculated with B. cinerea conidia (KB). Growth kinetics of strain Kh6 on wounded apples was determined and found to be not affected by the presence of B. cinerea conidia. Proteins were extracted from yeast pellets collected at both the exponential and stationary phases of strain Kh6 growth on apples. The evaluation of both extraction protocols indicates that more proteins were extracted with the SDS protocol and, according to 1-D assays, higher molecular weight proteins were obtained with the ‘urea/thiourea’ protocol and, regardless of the protocol used, more bands were obtained during the exponential phase. 2-D assays are currently underway and the corresponding results will be presented

The control of postharvest blue and green molds of citrus in relation with essential oil-wax formulations, adherence and viscosity.

peer reviewedThe use of wax coatings enriched with antifungals has significantly contributed to quality maintaining of harvested citrus fruit. On the other hand, interest in essential oils (EOs) as an alternative to synthetic fungicides has recently gained momentum. In this study, Cinnamomum zeylanicum EO was incorporated into a variety of commercial citrus waxes (shellac, carnauba, paraffin and polyethylene). The biological activity of these formulations against green and blue rots as well as their viscosity and adherence to the orange fruit surface were evaluated. Excellent disease control was achieved with C. zeylanicum EO incorporated in shellac and/or carnauba wax compared to other EO–wax formulations. Disease control by EO–waxes seems to depend not only on the volume that remains on the fruit skin, but also, probably on the retention of EO components on the fruit. Other factors such as formulation solubility, permeability to gases, and compatibility between EO compounds and those of waxes may also be involved in the improvement of EO efficacy. The present study may therefore allow a careful selection of ppropriate waxes for the elaboration of effective EO–wax formulations

Development of SCAR markers and a semi-selective medium for the quantification of strains Ach 1-1 and 1113-5, two Aureobasidium pullulans potential biocontrol agents.

peer reviewe

cDNA-AFLP analysis of Candida oleophila (strain O) genes differentially expressed during the biocontrol of Botrytis cinerea on harvested apples

peer reviewe

Etude des mécanismes de résistance au stress hydrique chez le blé dur (Triticum durum Desf.) : caractérisation de cultivars différant par leurs niveaux de résistance à la sécheresse et de variants somaclonaux sélectionnés in vitro

Doctorat en sciences biologiques -- UCL, 199

Le photopériodisme est impliqué dans le contrôle de la floraison chez Atriplex sp.

Doctorat en sciences biologiques -- UCL, 199

Physiological changes after exposure to and recovery from polyethylene glycol-induced water deficit in callus cultures issued from durum wheat (Triticum durum Desf.) cultivars differing in drought resistance

Calli obtained from three durum wheat (Triticum durum Desf.) cultivars with different drought resistance levels were exposed for 30 days to a polyethylene glycol-induced water deficit followed by 30 days of recovery. Relative growth rate, percent dry weight, osmotic potential and the changes in inorganic and organic solutes were determined at the end of both the stress and the recovery periods. After the stress period, calli derived from the drought resistant cultivars, particularly Omrabi 5 and to some extent Haurani, showed a less reduced relative growth rate, lower osmotic potential and higher proline and other amino acid accumulations as compared with the sensitive cultivar Kabir I. Drought resistance could also be associated with a better protection of enzymes involved in nitrogen metabolism. At the end of the recovery period, most of the quantified parameters, except osmotic potential, recovered completely, indicating the reversibility of the changes induced by water deficit at the plant cell level in durum wheat. Our data show that a correlation exists between performances of the cultivars under drought and the responses of callus cultures to PEG-induced water deficit; this suggests that: in durum wheat the degree of resistance to drought at the plant level depends, at least in part, on the existence of mechanisms operating at the cellular level

Physiological changes after exposure to and recovery from polyethylene glycol-induced water deficit in roots and leaves of durum wheat (Triticum durum Desf.) cultivars differing in drought resistance

The effects of water stress on the behaviour of hydroponically-grown seedlings of 3 durum wheat ( Triticum durum Desf.) cvs. differing in drought resistance (Kabir 1, drought sensitive; Omrabi 5 and Haurani, drought resistant) were investigated under controlled environmental conditions. Fresh weight (FW), water content (WC), osmotic potential (Psi(s)), organic and inorganic solute concentrations in roots and shoots were measured after 7 days of exposure to polyethylene glycol (PEG at 0, 10 or 20 %) and after 2 and 7 days of recovery following stress relief. Water stress decreased FW WC and Psi s, and increased root to shoot ratio (R/S) and soluble sugar, proline and other amino acid concentrations in both roots and leaves of all cvs. Water stress effect on inorganic solutes was different depending on the ion nature and on the plant part. Most of the significant changes were recorded in response to 20 % PEG. Roots and shoots roughly reacted in the same way to water stress but differed in terms of the intensity and rapidity of the responses. After stress relief, almost all parameters returned to control level; however, for some of them, roots and shoots differed in the rapidity of their recovery. Growth parameters as well as organic solute accumulation revealed differences in the behaviour of the 3 different cvs. when confronted to water stress. Our results demonstrated the high plasticity of durum wheat at the vegetative stage and suggest that the maintenance of higher root growth and osmotic adjustment in water stress conditions could confer an improved resistance of this species to drought