Emma W. Gachomo

The reactive oxygen species network pathways: an essential prerequisite for perception of pathogen attack and the acquired disease resistance in plants

Availability of complete Arabidopsis(Arabidopsis thaliana) and rice(Oryza sativa) genome sequences, together with molecular recourses of functional genomics and proteomics have revolutionized our understanding of reactive oxygen species (ROS) signalling network mediating disease resistance in plants. So far, ROS have been associated with aging, cellular and molecular alteration in animal and plant cells. Recently, concluding evidences suggest that ROS network is essential to induce disease resistance and even to mediate resistance to multiple stresses in plants. ROS are obligatory by-products emerging as a result of normal metabolic reactions. They have the potential to be both beneficial and harmful to cellular metabolism. Their dual effects on metabolic reactions are dosage specific. In this review we focus our attention on cellular ROS level to trigger beneficial effects on plant cells responding to pathogen attack. By exploring the research related contributions coupled with data of targeted gene disruption, and RNA interference approaches, we show here that ROS are ubiquitous molecules of redox-pathways that play a crucial role in plant defence mechanism. The molecular prerequisites of ROS network to activate plant defence system in response to pathogen infections are here underlined. Bioinformatic tools are now available to scientists for high throughput analysis of cellular metabolisms. These tools are used to illustrate crucial ROS-related genes that are involved in the defence mechanism of plants. The review describes also the emerging findings of ROS network pathways to modulate multiple stress resistance in plants.

The molecular initiation and subsequent acquisition of disease resistance in plants

Interactions between disease resistance (R) genes in plants and their corresponding pathogen avirulence (Avr) genes are the key determinants of whether a plant is susceptible or resistance to a pathogen attack. Evidence has emerged that these gene-for-gene interactions in the perception of pathogenic invasions and development of acquired resistance in plants involve different molecular and hormonal transduction pathways, which are still poorly understood. It has become apparent that plants actively produce several phytohormones such as ethylene, jasmonate, salicylic acid, and reactive oxygen intermediates prior to upregulation of R genes. The physiological role of these molecules in plant resistance to pathogens is beginning to attract attention. The use of transgenic plants in recent attempts, including development of mutants with altered R genes, has provided new insights into the mechanisms involved in pathogen perception, signal transduction and subsequent resistance to disease in plants. This review tries to summarize current knowledge of pathogen-related genes in plants, and how they can be use to improve disease resistance in agronomically valuable plants. It also describes the molecular basis of defense mechanisms in plants under pathogen attack. (African Journal of Biotechnology: 2003 2(2): 26-32)

A home made kit for plasmid DNA mini-preparation

Many methods have been used to isolate plasmid DNA, but some of them are time consuming especially when extracting a large number of samples. Here, we developed a rapid protocol for plasmid DNA extraction based on the alkaline lysis method of plasmid preparation (extraction at pH 8.0). Using this new method, a good plasmid preparation can be made in approximately one hour. The plasmids are suitable for any subsequent molecular applications in the laboratory. By applying the recommendations to avoid contaminations and to maximize the plasmid yield and quality during extraction, this protocol could be a valuable reference especially when analyzing a large number of samples. (African Journal of Biotechnology: 2003 2(4): 87)

Paenibacillus polymyxa, Bacillus licheniformis and Bradyrhizobiumjaponicum IRAT FA3 Promote Faster Seed Germination Rate, Growth andDisease Resistance under Pathogenic Pressure

The detriment of chemical fungicides and pesticides have proven a hindrance in sustainable agriculture and therefore motivated efforts in finding biologically natural alternatives to control plant pathogen infections. The effect of the plant growth promoting rhizobacteria (PGPR), Paenibacillus polymyxa, Bacillus licheniformis and Bradyrhizobium japonicum IRAT FA3 on seed germination and their biocontrol capability against Pseudomonas syringae pv malculiola in Arabidopsis thaliana were studied in this work. The data presented here demonstrates that the presence of these PGPR promotes the seed germination rate up to 145% higher than the untreated control. This study also describes the symptom isolation observed in Arabidopsis leaves infected with P. syringae, which prevented the infected plants to undergo full-fledged chlorosis suggesting that these PGPR can be possible options in acting as natural biocontrol agents against P. syringae and probably other plant pathogens.

Phenotypic characters of yeasts isolated from kpete-kpete, a traditional starter of a Benin opaque sorghum beer

Opaque sorghum beers are the most consumed African alcoholic beverages. Tchoukoutou is one of the Benin opaque sorghum beers. Its fermentation process is carried out using a traditional starter called kpete-kpete. The present study characterized and identified the yeasts isolated from kpete-kpete. A total of 24 samples of kpete-kpete were collected from eight different commercial processing sites in Northern Benin. The mean values of the pH, titrable acidity, dry matter content and refractive index for all samples were respectively 3.58; 0.07% as lactic acid; 16.61% and 7.0. The mean counts of yeasts was 9.24 log cfu/ml. Based on their phenotypic characters and their assimilation profiles, 49 yeasts were isolated and found to belong to five genera with seven species. Seventy one percent (71%) of the isolates were identified as Saccharomyces cerevisiae. Key words : Sorghum beer, tchoukoutou, kpete-kpete, yeast, Saccharomyces cerevisiae.

Control of Major Diseases in Horticulture

Emma W. Gachomo1,2, Jose C. Jimenez-Lopez3, Adechola P. P. Kayode4, Lamine Baba-Moussa5 and Simeon O. Kotchoni1,2 1Department of Biology, Rutgers University, Camden, 2Center for Computational and Integrative Biology, Rutgers University, Camden, 3Department of Biochemistry, Cell and Molecular Biology of Plant, Estacion Experimental del Zaidin, Consejo Superior de Investigaciones Cientificas, Granada, 4Departement de Nutrition et Sciences Alimentaires, Faculte des Sciences Agronomiques, Universite d’Abomey-Calavi, Cotonou, 5Laboratoire de Biologie et de Typage Moleculaire en Microbiologie, Faculte des Sciences et Techniques, Universite d’Abomey-Calavi, Cotonou, 1,2USA 3Spain 4,5Benin