Promotion of Bamboo Mosaic Virus Accumulation in Nicotiana benthamiana by 5′→3′ Exonuclease NbXRN4

Abstract

Bamboo mosaic virus (BaMV) has a 6.4-kb (+) sense RNA genome with a 5′ cap and a 3′ poly(A) tail. ORF1 of this potexvirus encodes a 155-kDa replication protein responsible for the viral RNA replication/transcription and 5′ cap formation. To learn more about the replication complex of BaMV, a protein preparation enriched in the 155-kDa replication protein was obtained from Nicotiana benthamiana by a protocol involving agroinfiltration and immunoprecipitation. Subsequent analysis by SDS-PAGE and mass spectrometry identified a handful of host proteins that may participate in the viral replication. Among them, the cytoplasmic exoribonuclease NbXRN4 particularly caught our attention. NbXRN4 has been shown to have an antiviral activity against Tomato bushy stunt virus and Tomato mosaic virus. In Arabidopsis, the enzyme could reduce RNAi- and miRNA-mediated RNA decay. This study found that downregulation of NbXRN4 greatly decreased BaMV accumulation, while overexpression of NbXRN4 resulted in an opposite effect. Mutations at the catalytically essential residues abolished the function of NbXRN4 in the increase of BaMV accumulation. Nonetheless, NbXRN4 was still able to promote BaMV accumulation in the presence of the RNA silencing suppressor P19. In summary, the replication efficiency of BaMV may be improved by the exoribonuclease activity of NbXRN4.

Harnessing host ROS-generating machinery for the robust genome replication of a plant RNA virus

“…6). Recently, it has been shown that RBOH proteins are also copurified with bamboo mosaic virus RdRp (46). Generation of ROS is a common response during pathogen infection, and RBOH is highly conserved in plants.…”

Polysomes, Stress Granules, and Processing Bodies: A Dynamic Triumvirate Controlling Cytoplasmic mRNA Fate and Function

“…This may reflect reliance on AtXRN4 for the degradation of specific transcripts (Rymarquis et al, 2011). Nevertheless, XRN4-mediated translational repression and mRNA decay play a role in seed dormancy and germination (Basbouss-Serhal et al, 2017), ethylene signaling (Li et al, 2015;Merchante et al, 2015), heat stress response and tolerance (Merret et al, 2013;Nguyen et al, 2015), and viral defense (Jaag and Nagy, 2009;Peng et al, 2011;Lee et al, 2016). An alternative explanation is that, in the absence of XRN4 function, the 39-59 degradation pathways described below may maintain homeostasis.…”

Mitogen‐activated protein kinase phosphatase 1 reduces the replication efficiency of Bamboo mosaic virus in Nicotiana benthamiana

“…A). The inherent RNA‐dependent RNA polymerase (RdRp) activity of P 30 using the endogenous SF4 RNA as the template was then initiated by adding NTP and [α‐ 32 P]UTP into P 30 suspension as the previous description (Lee et al, ). Apparently, the amount of the de novo synthesized α‐ 32 P‐labeled SF4 decreased to ~ 40% compared with the control if the plant had also been agroinfiltrated with pEpNbMKP1 (Fig.…”

“…The cDNA copies of NbMKP1 , both wild type and the C201S mutant, were also inserted into the binary plasmid pEpyon‐32K to become pEpNbMKP1 and pEpNbMKP1(C201S), which were used to overexpress NbMKP1 in plant leaves via agroinfiltration. For NbMKP1 ‐silencing experiments, a 212‐nt cDNA fragment of NbMKP1 (592‐803 nts) was inserted into pTRV2 via restriction sites Eco RI and Xho I (Lee et al, ). The BaMV infectious clone pCBG was used to direct the constitutive synthesis of a GFP ‐carrying BaMV transcript in plant cells (Lin et al, ).…”