A viral suppressor of RNA silencing inhibits ARGONAUTE 1 function by precluding target RNA binding to pre-assembled RISC

In most eukaryotes, RNA silencing is an adaptive immune system regulating key biological processes including antiviral defense. To evade this response, viruses of plants, worms and insects have evolved viral suppressors of RNA silencing proteins (VSRs). Various VSRs, such as P1 from Sweet potato mild mottle virus (SPMMV), inhibit the activity of RNA-induced silencing complexes (RISCs) including an ARGONAUTE (AGO) protein loaded with a small RNA. However, the specific mechanisms explaining this class of inhibition are unknown. Here, we show that SPMMV P1 interacts with AGO1 and AGO2 from Arabidopsis thaliana, but solely interferes with AGO1 function. Moreover, a mutational analysis of a newly identified zinc finger domain in P1 revealed that this domain could represent an effector domain as it is required for P1 suppressor activity but not for AGO1 binding. Finally, a comparative analysis of the target RNA binding capacity of AGO1 in the presence of wild-type or suppressor-defective P1 forms revealed that P1 blocks target RNA binding to AGO1. Our results describe the negative regulation of RISC, the small RNA containing molecular machine

A lucerna szimbiotikus nitrogénkötés kialakításában kulcsfontosságú szerepet játszó receptor fehérje molekuláris jellemzése = Molecular characterization of a receptor protein playing an essential role in symbiotic nitrogen fixation of alfalfa.

A pillangósvirágú növények egyedülálló szimbiotikus kapcsolatban állnak a rizóbium baktériumokkal, ami egy speciális növényi szerv, a gyökérgümő képződéséhez vezet, ahol a légköri nitrogénkötés történik. A növény-baktérium kapcsolat kölcsönös jelcserét indít be a gümőképződés fejlődési programban. Napjainkban több protein-kinázt azonosítottak, amelyek feltehetőleg a nodulációhoz vezető szignál transzdukcióban vesznek részt. A szignál kaszkád a Nod faktor felismerés és továbbítás (NORK rendszer) során vezet el a nodulációig. A NORK rendszer egyik eleme a NORK (NOdulation Reception Kinase) fehérje, amelyik több más kinázzal együttműködve juttatja el a jelet a Nod-faktor érzékelésétől a gümő képzéséig. Izoláltuk a NORK membrán fehérjét lucerna gyökér extraktumból. Két-dimenziós elektroforézissel elválasztottuk és immunoblotton azonosítottuk. Eredményeink alátámasztására, epitop jelzett NORK fehérje tranziens expresszióját igazoltuk dohánylevélben Agrobacterium tumefaciens infiltrálás segítségével. A NORK fehérje szerepének és funkciójának tisztázására a NORK rendszer más kináz fehérjéivel való kapcsolatát (LYK3, NFP) is vizsgáltuk fehérje-fehérje kapcsolatok kimutatásával. Az LRR1 típusú növényi receptor-szerű kinázok (RLK) filogenetikai analízise alapján arra következthetünk, hogy a NORK/SYMRK fehérje homológjai egy jól elkülönülő monofiletikus csoportot alkotnak az LRR1 RLK családon belül, és pillangósvirágú növényeken kívüli taxonokban is megtalálhatók. | Legume roots engage in a unique symbiotic relationship with rhizobia, in which special plant organs, the nodules, are formed and support nitrogen fixation. The plant-bacteria interactions involve the exchange of signals that trigger specific cellular and developmental programs in both. Recently several protein kinases have identified, which are participating in specialized signal transduction pathways that culminate in the induction of a transcriptional program of nodulation.The signal cascade leading to nodulation is part of the Nod-factor perception/ transduction system (the NORK system) active in legume roots. The identified NOdulation Receptor Kinase, NORK, is an integral component of the signalling pathway, in which the coordinated interaction of the components is needed for Nod-factor signal perception and transduction. Isolation of NORK from root extract of alfalfa, separation by 2D and detection on immunoblot were done. Epitop tagged NORK were transiently expressed in tobacco leaves by Agrobacterium tumefaciens infiltration. To justify interactions with other kinases in the NORK system (LYK3, NFP), we investigated the role and function of NORK by protein-protein interaction studies. Phylogenetic analysis of the LRR1-type plant receptor like kinases (RLK) revealed that homologues of the NORK/SYMRK protein constitute a single monophyletic clade within the LRR1 RLK family and members of this group exist in several non-legume plants

Conventional PCR primers for the detection of grapevine pathogens disseminated by propagating material

Polymerase chain reaction driven by sequence specific primers has become the most widely used diagnostic method to detect andidentify plant pathogens. The sensitive and cost-effective pathogen detection is exceptionally important in the production of propagatingmaterial. In this paper we have collected primer sequence data from the literature for the detection of the most important grapevine pathogensdisseminated by propagating stocks by conventional polymerase chain reaction. Basic protocols to obtain template nucleic acids have alsobeen briefly rewieved

Primers designed for the detection of grapevine pathogens spreading with propagating material by quantitative real-time PCR

Several grapevine pathogens are disseminated by propagating material as systemic, but latent infections. Their detection andidentification have a basic importance in the production and handling of propagating stocks. Thus several sensitive and reliable diagnosticprotocols mostly based on molecular techniques have been developed. Of these methods quantitative real-time PCR (q-PCR) has recently gotan emerging importance. Here we collected primer data for the detection and identification of grapevine pathogens which are important inthe production of propagating stocks by q-PCR. Additional novel techniques that use DNA amplification, hybridization and sequencing arealso briefly reviewed