Browsing by Subject "silencing suppressors"

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  • Streng, Janne (Helsingfors universitet, 2013)
    RNA silencing is a sequence specific RNA degradation mechanism which is used by plants to regulate gene expression and to combat virus infections. However, viruses have developed so called silencing suppressors, which can prevent and interfere silencing reaction by many ways. For example, virus proteins can bind to maintaining proteins of the silencing reaction or to molecules which are responsible for signaling of the silencing reaction. This thesis focused on the study of protein-protein-interactions between known silencing suppressors of crini- and potyviruses and four maintaining plant proteins of RNA silencing. Protein-protein-interactions were studied using the yeast two-hybrid system (YTHS) and the bimolecular fluorescence complementation assay (BiFC). The latter method enables visualization of the studied protein interactions in plant cells. Protein expression of the cloned genes in yeast vectors were studied by using western blot. BiFC analysis was focused on protein interactions which were found by YTHS. This study detected three previously unknown protein interactions. Two virus proteins were found for the first time to bind directly to silencing maintaining proteins that are known to be targets of other silencing suppressors. Because the functions of these silencing maintaining proteins are known, it is possible that the three interactions described in this study interfere RNA silencing by impeding the functions of the plant proteins.
  • Marttinen, Eeva M.; Lehtonen, Mikko T.; van Gessel, Nico; Reski, Ralf; Valkonen, Jari P.T. (2022)
    Plant viruses are important pathogens able to overcome plant defense mechanisms using their viral suppressors of RNA silencing (VSR). Small RNA pathways of bryophytes and vascular plants have significant similarities, but little is known about how viruses interact with mosses. This study elucidated the responses of Physcomitrella patens to two different VSRs. We transformed P. patens plants to express VSR P19 from tomato bushy stunt virus and VSR 2b from cucumber mosaic virus, respectively. RNA sequencing and quantitative PCR were used to detect the effects of VSRs on gene expression. Small RNA (sRNA) sequencing was used to estimate the influences of VSRs on the sRNA pool of P. patens. Expression of either VSR-encoding gene caused developmental disorders in P. patens. The transcripts of four different transcription factors (AP2/erf, EREB-11 and two MYBs) accumulated in the P19 lines. sRNA sequencing revealed that VSR P19 significantly changed the microRNA pool in P. patens. Our results suggest that VSR P19 is functional in P. patens and affects the abundance of specific microRNAs interfering with gene expression. The results open new opportunities for using Physcomitrella as an alternative system to study plant-virus interactions.