Managing the selling force in Algerian companies: a field study of a sample of Algerian companies

الهدف من هذا البحث هو معرفة كيفية تسيير القوة البيعية من طرف المؤسسات الجزائرية، ولتحقيق ذلك قمنا بتصميم استبيان وتوزيعه على عينة متكونة من 80 مؤسسة. وقد بينت نتائج هذه الدراسة أن المؤسسات الجزائرية تولي أهمية للقوة البيعية لتحقيق أهدافها المرجوة، وذلك من خلال استعمال قوة بيعية متكونة من رجال بيع الذين تختارهم المؤسسة بعناية فائقة، معتمدة على مجموعة من المعايير، كما تقوم بتدريبهم على مختلف المناهج البيعية الفعالة، ومتابعة أدائهم ومكافئتهم.This study aims to identify the way how the sales force is managed by the Algerian companies; and, for this purpose, we designed a questioner which given to a sample of 80 companies. And, the study's results illustrated that those companies gives importance to the sales force to realise its intended objectives throughout using that force which composed of salespeople whom been chosen carefully basing on different criteria, as well as it trains them on various effective sales methods with tracking their performance and efficienc

Pharmacological analysis of transmission activation of two aphid-vectored plant viruses, turnip mosaic virus and cauliflower mosaic virus

Turnip mosaic virus (TuMV, family Potyviridae) and cauliflower mosaic virus (CaMV, family Caulimoviridae) are transmitted by aphid vectors. They are the only viruses shown so far to undergo transmission activation (TA) immediately preceding plant-to-plant propagation. TA is a recently described phenomenon where viruses respond to the presence of vectors on the host by rapidly and transiently forming transmissible complexes that are efficiently acquired and transmitted. Very little is known about the mechanisms of TA and on whether such mechanisms are alike or distinct in different viral species. We use here a pharmacological approach to initiate the comparison of TA of TuMV and CaMV. Our results show that both viruses rely on calcium signaling and reactive oxygen species (ROS) for TA. However, whereas application of the thiol-reactive compound N-ethylmaleimide (NEM) inhibited, as previously shown, TuMV transmission it did not alter CaMV transmission. On the other hand, sodium azide, which boosts CaMV transmission, strongly inhibited TuMV transmission. Finally, wounding stress inhibited CaMV transmission and increased TuMV transmission. Taken together, the results suggest that transmission activation of TuMV and CaMV depends on initial calcium and ROS signaling that are generated during the plant's immediate responses to aphid manifestation. Interestingly, downstream events in TA of each virus appear to diverge, as shown by the differential effects of NEM, azide and wounding on TuMV and CaMV transmission, suggesting that these two viruses have evolved analogous TA mechanisms

Etude du cycle du Cauliflower mosaic virus : aspect de sa réplication, son accumulation et sa transmission

UMR BGPI - Equipe 2; thèse confidentielle jusqu'en juin 2011 Diplôme : Dr. Ing.Cauliflower mosaic virus (CaMV) is considered, on the molecular level, as one of the best characterized plant viruses. Nonetheless, several aspects of its replication cycle remain unknown. The aim of the present work was to better understand the CaMV infection cycle by studying the early phases of its replication, its accumulation in a host, and finally its preparation for vector transmission. We show that the electron-lucent inclusion bodies, viral inclusions that form in the cytoplasm of infected cells, are specialized in and mandatory for acquisition of CaMV by its aphid vectors. Their one and only function is preparation of transmission, we define them therefore as "transmission bodies". We then measured a key parameter of the CaMV infection cycle, which is the time necessary for the completion of one round of replication in a cell. We show that this minimal replication time (21 h) is invariable in distinct hosts, even from different families. Finally, to better understand intra-host dynamics of CaMV populations, we studied evolution of the viral charge on the cellular level and in a leaf during establishment of systemic infection. The results indicate an unexpected cell-to-cell variability of the viral load. Accumulation kinetics of CaMV in a leaf shows that virus continues to accumulate in the limb after all leaf cells are infected, indicating that the accumulation occurs at the cellular and not at the tissue level. We exclude secondary infection of cells as a cause for this accumulation and provide evidence that successive replication rounds contribute to the increase of the cellular viral load. Taken together, the presented work increases significantly our understanding of the CaMV life cycle, by detailing some events related to it and their respective position in the time, from the initial infection of a cell until the transmission by vector.Le Cauliflower mosaic virus (CaMV) est considéré comme un des virus de plantes les mieux caractérisés sur le plan moléculaire, mais plusieurs aspects de son cycle de vie demeurent inconnus. Le présent travail s’articule autour de la compréhension du cycle infectieux du CaMV en étudiant les phases précoces de sa réplication, son accumulation dans son hôte et enfin sa préparation pour la transmission par vecteur. Nous avons montré que les corps clairs, des inclusions virales spécifiques qui se forment dans le cytoplasme des cellules infectées, sont bien des structures spécialisées et obligatoires pour l'acquisition du CaMV par les pucerons vecteurs. Leur seule et unique fonction est de préparer la transmission, et nous les définissons désormais comme les « Transmission bodies ». Nous avons ensuite mesuré un paramètre dynamique clef du cycle infectieux du CaMV, qui est le temps minimum nécessaire à l’accomplissement d’un cycle de réplication dans une cellule infectée. Nous montrons en outre que ce temps minimal de réplication reste invariable chez différents hôtes, même appartenant à des familles botanique différentes. Enfin, dans le but de mieux comprendre la dynamique intra-hôte des populations du CaMV, nous avons examiné l’évolution de la charge virale au niveau cellulaire et au niveau d’une feuille durant l’établissement de l’infection systémique. Les résultats révèlent une variabilité inattendue de la charge virale d'une cellule à l'autre. Les cinétiques d'accumulation du CaMV dans une feuille montrent que le virus s'accumule dans la feuille bien au-delà du moment où toutes les cellules du limbe sont infectées. Ceci indique que l'accumulation s’explique majoritairement au niveau cellulaire et non pas tissulaire. Dans le mécanisme d’accumulation du CaMV, nous avons pu exclure une surinfection des cellules et mettre en évidence l’existence de plusieurs réplications successives au sein d’une même cellule. L’ensemble de ces travaux alimente significativement notre compréhension du cycle de vie du CaMV, en détaillant les phénomènes qui s’enchaînent, et leur positionnement respectifs dans le temps, depuis l’infection initiale dans une cellule jusqu’à la transmission par vecteu

Determination of replication cycle duration of Cauliflower mosaic virus

International audienceIntroduction The replication duration represents a crucial step in the life cycle of a virus which influences many parameters of virus biology such as the kinetics of its accumulation in the infected cells and tissues, in the development of the infection within the host and beyond, epidemiology and viral evolution. Despite its central role during viral infection, quantitative parameters of the replication cycle such as its duration are largely unknown, especially for plant viruses. This lack of information conduct us to design an experimental system for measuring the replication cycle duration of Cauliflower mosaic virus (CaMV). Objective Determination of the replication cycle duration of CaMV in Arabidopsis thalianaprotoplasts. We define the duration of replication as the time required for a viral particle, to replicate its genome and form new viral particles after its entry in the host cell...

Étude du cycle cellulaire du Cauliflower mosaic virus

National audienc

Temps de génération et dynamique d'invasion du CaMV dans une feuille systémique

National audienceLa réplication représente une étape cruciale dans le cycle cellulaire d’un virus puisqu’elle est à la base de son accumulation dans les tissus de l’hôte. Malgré ce rôle central, nous avons peu de données concernant les paramètres quantitatifs et dynamiques de la réplication chez les phytovirus. Nous nous sommes intéressés à l’étude d’un paramètre quantitatif de réplication du Cauliflower mosaic virus qui est le temps de génération. Connaître ce type de donnée est fondamentale à la compréhension de l’évolution virale. Positionner la réplication par rapport à d’autres phénomènes qui se produisent dans la cellule infectée, permet de mieux comprendre la stratégie d’invasion cellulaire. Nous présenterons les résultats obtenus sur le temps de génération du CaMV dans plusieurs plantes hôtes. Nous nous intéressons aussi à la dynamique de l’invasion virale dans des tissus systémiques. Nous présenterons des résultats relatifs à la vitesse d’infection des cellules et l’accumulation de la charge virale à l’échelle cellulaire et des tissus

Evaluation of the minimal replication time of Cauliflower mosaic virus in different hosts

UMR BGPI Equipe 2 Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699International audienceThough the duration of a single round of replication is an important biological parameter, it has been determined for only few viruses. Here, this parameter was determined for Cauliflower mosaic virus (CaMV) in transfected protoplasts from different hosts: the highly susceptible Arabidopsis and turnip and Nicotiana, benthamiana, where CaMV accumulates only slowly. Four methods of differing sensitivity were employed: labelling of (1) progeny DNA and (2) capsid protein, (3) immunocapture PCR,, and (4) progeny-specific PCR. The first progeny virus was detected about 21 h after transfection. This value was confirmed by all methods, indicating that our estimate was not biased by the sensitivity of the detection method, and approximated the actual time required for one round of CaMV replication. Unexpectedly, the replication kinetics were similar in the three hosts; suggesting that slow accumulation of CaMV in Nicotiana plants is determined by non-optimal interactions in other steps of the infection cycl

Interaction between plant responses and transmission of TuMV by Myzus persicae

BGPI : équipe 2Many viruses are transmitted by aphids in a non-circulative manner. This indicates that when aphids feed on an infected plant, the transmitted virus particles attach within seconds to the stylets, and are transported in them to a new host plant. This is the case of the Caulimovirus Cauliflower mosaic virus (CaMV), which follows the molecular strategy called “transmission helper component” for transmission. Its viral helper component, protein P2, intervenes by creating the molecular link between virus particles and stylets. In presence of aphid vectors, CaMV forms transmissible P2-virus complexes in the cell. This phenomenon, called "Transmission Activation(TA)", boosts CaMV transmission and depends on CaMV interfering with aphid-plant responses. We are interested in the transmission of the Potyvirus Turnip mosaic virus (TuMV), another non circulative virus using the transmission helper component strategy with its viral protein Helper Component Protease (HC-Pro). We wanted to determine whether this virus also uses TA. Aphid transmission tests with Myzus persicae were carried out using infected protoplasts as virus source that were incubated with different reagents, mimicking plant defense responses, before the transmission tests. The results showed that a blocker of calcium signaling, LaCl3, reduced transmission while the reactive oxygen species (ROS), H2O2, activated it. This suggests that different plant defense responses modify the cellular environment in which HC-Pro is located, induce TA of TuMV and therefore its acquisition by aphids. Moreover, western blotting showedthat LaCl3 inhibited and H2O2 induced formation of intermolecular cysteine bonds linking HC-Prooligomers. Taken together, our results demonstrate that TuMV transmission can be activated, that calcium signaling and ROS are involved in it and that it correlates with oxidation of HC-Pro. Thus, TuMV is a second example for the TA phenomenon, and a model of Potyvirus transmission

Caractérisation des mutants du Cauliflower mosaic virus altérés dans la morphogenèse des corps d'inclusion clairs

National audienc

Transmission activation of potyviruses

BGPI : équipe 2Potyviruses are transmitted by aphids, like hundreds of other plant viruses, in a non-circulative manner, and following the molecular strategy called "transmission helper component". This indicates that when aphids feed on an infected plant, the transmitted virus particles attach within seconds to the stylets (mouthparts of aphids), and are transported to a new host plant. The connection between the Potyvirus virions and the stylets is not direct, a transmission helper factor, the viral protein Helper Component Protease (HC-Pro), intervenes by creating the molecular link between virions and stylets. The Caulimovirus Cauliflower mosaic virus, another non-circulative virus using a different transmission helper component, P2, responds to the presence of aphid vectors on the plant by forming only then transmissible P2-virion complexes. This strategy, called "Transmission Activation (TA)", controls CaMV transmission. Here, the transmission of Potyviruses has been tested in order to determine if these viruses also follow this strategy. The pathosystems tested are turnip/Turnip mosaic virus, lettuce/Lettuce mosaic virus and tobacco/Potato Virus Y. Aphid transmission tests with green peach aphids (Myzus persicae) were carried out using infected protoplasts as virus source that were incubated with various substances before the transmission tests. The results showed that a blocker of calcium signaling, Lanthanum(III) chloride (LaCl3), inhibited transmission while the reactive oxygen species (ROS), hydrogen peroxide (H2O2), activated it. Western blotting established that LaCl3 inhibited and H2O2 induced formation of intermolecular cystein bonds linking HC-Pro oligomers. Taken together, our results show that Potyvirus transmission can be activated, that calcium signaling and ROS are involved in it and that it correlates with oxidation of HC-Pro. Thus, Potyviruses are a second example for the TA phenomenon, and a model of Potyvirus transmission is presented