Sequence analysis and genomic organization of Aphid lethal paralysis virus: a new member of the family Dicistroviridae

The complete nucleotide sequence of the genomic RNA of an aphid-infecting virus, Aphid lethal paralysis virus (ALPV), has been determined. The genome is 9812 nt in length and contains two long open reading frames (ORFs), which are separated by an intergenic region of 163 nt. The first ORF (5' ORF) is preceded by an untranslated leader sequence of 506 nt, while an untranslated region of 571 nt follows the second ORF (3' ORF). The deduced amino acid sequences of the 5' ORF and 3' ORF products respectively showed similarity to the non-structural and structural proteins of members of the newly recognized genus Cripavirus (family Dicistroviridae). On the basis of the observed sequence similarities and identical genome organization, it is proposed that ALPV belongs to this genus. Phylogenetic analysis showed that ALPV is most closely related to Rhopalosiphum padi virus, and groups in a cluster with Drosophila C virus and Cricket paralysis virus, while the other members of this genus are more distantly related. Infectivity experiments showed that ALPV can not only infect aphid species but is also able to infect the whitefly Trialeurodes vaporariorum, extending its host range to another family of the order Hemipter

Une maladie foliaire de Solanum gilo Raddli due à Stemphylium floridanum Hannon & Weber, en Côte-d'Ivoire

International audienc

Interactions hote-parasite (Stemphylium floridanum, Hannon et Weber - Solanum gilo, Raddli) aspects symptomatologiques ultrastructuraux et biochimiques

INIST T 77321 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Recherches de fongicides actifs sur Stemphylium floridanum Hannon et Weber, parasite de Solanum gilo Raddli

International audienc

Caractérisation biologique et moléculaire de virus infectant les pucerons et évaluation de leur potentiel comme biopesticides

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

La résistance du cotonnier Gossypium hirsutum à la bactériose causée par Xanthomonas campestris pathovar malvacearum (rôle du gène GhLOX1 dans la réaction hypersensible)

La RH est une réaction de défense. L interaction entre G.hirsutum et Xcm repose sur le concept gène-à-gène. L infection du cultivar Réba B50 possédant les gènes R B2B3 par Xcm18 conduit à une RH associée à une activité LOX, responsable de la peroxydation des lipides, et à la transcription du GhLOX1. Premièrement, 6 génotypes de G.hirsutum contenant divers gènes R ont été retenus pour analyser la variabilité de la réponse LOX suite à l infection par Xcm1, 18 ou 20. Notre étude a porté sur plusieurs critères, le phénotype, la perte en eau, l activité LOX et la transcription du GhLOX1. Les résultats montrent une variabilité du phénotype RH en fonction des sources de résistances. Pour chaque type d interaction incompatible, l activité LOX et la transcription du GhLOX1 révèlent une augmentation significative corrélée à l apparition des symptômes RH et à la diminution de la teneur en eau. La réponse LOX est conservée lors de la RH, quelle que soit la race de Xcm ou le génotype. Le GhLOX1 considère comme un marqueur moléculaire de la résistance spécifique du cotonnier à Xcm. Deuxièmement, le rôle du GhLOX1dans la mise en place de la RH en analysant sa fonction potentielle par surexpression. Des cotylédons ont été transformés avec la séquence codante GhLOX1 fusionnée au CaMV35S. Ces cotylédons transformés ont révélé (i) une activité LOX significativement supérieure à celle des cotylédons témoins montrant que le GhLOX1 code pour une protéine active et (ii) un phénotype sans modifications apparentes par rapport à celui des cotylédons non transformées, sauf dans certains contextes d interactions cotonnier/Xcm où la surexpression de ce gène induit l apparition de symptômes de type RH. L effet de l agro-infiltration sur l expression de certains gènes pendant la transformation a révélé l induction précoce et non spécifique de l expression de gènes de défense. Ces travaux constituent une première étape dans l analyse fonctionnelle du GhLOX1 dans la résistance spécifique du cotonnier à XcmThe HR is a defense strategy. The interaction between G.hirsutum and Xcm is governed by the gene-for-gene concept. The infection of the cultivar Reba B50 that contains B2B3 R genes by race Xcm18 leads to a HR associated with a LOX activity response involved in peroxidation of lipids and with transcription of GhLOX1. First, 6 genotypes of G. hirsutum containing various R genes were tested to analyze the variability of the LOX response following the infection by Xcm1, 18 or 20. Several criteria were investigated including the phenotype, the water loss, the LOX activity and GhLOX1 transcription. The results showed variation in HR phenotype according to the tested R genes. For each type of the incompatible interaction, LOX activity and transcription of GhLOX1 were always significantly increased paralleled the apparition of the HR symptoms and the decrease in the water content. LOX response (enzymatic activity and GhLOX1 transcription) is associated with HR whatever the genotype of both Xcm races and cotton plant. Thus, the GhLOX1 consider as a molecular marker of the cotton specific resistance to Xcm. Second, the role of the GhLOX1 gene in the execution of the cotton HR to Xcm by analyzing its possible function by over-expression, the cotyledons were transformed with the GhLOX1 coding sequence fused to the CaMV35S. These transformed cotyledons revealed (i) a LOX activity significantly higher than that detected in the control, showing that the GhLOX1 encodes for an active protein and (ii) that the phenotype of these cotyledons was indistinguishable as compared to the non transformed cotyledons, except when the HR symptoms were induced in some GhLOX1-over-expressed cotyledons. The effect of agro-infiltration on expression of some plant genes during the transformation revealed early and nonspecific induction of the expression of defense genes. This work constitutes a preliminary investigation for the functional analysis of the GhLOX1 in order to assess its role in the cotton specific resistance to XcmNANCY-INPL-Bib. électronique (545479901) / SudocSudocFranceF

Accumulation of phytoalexins in leaves of plane tree (Platanus spp.) expressing susceptibility or resistance to Ceratocystis fimbriata f.sp.platani

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Can plants use an entomopathogenic virus as a defense against herbivores?

International audienceIt is by now well established that plants use various strategies to defend themselves against herbivores. Besides conventional weapons such as spines and stinging hairs and sophisticated chemical defenses, plants can also involve the enemies of the herbivores in their defense. It has been suggested that plants could even use entomopathogens as part of their defense strategies. In this paper, we show that Brassica oleraceae plants that are attacked by Myzus persicae aphids infected with an entomopathogenic parvovirus (M. persicae densovirus) transport the virus through the phloem locally and systematically. Moreover, healthy aphids that fed on the same leaf, but separated from infected aphids were infected via the plant. Hence, this is proof of the principle that plants can be vectors of an insect virus and can possibly use this virus as a defense against herbivores