Juan Antonio García
Group Leader
Carmen Simón
Group Leader
Research summary
Plant viruses depend largely on host factors to replicate in the cell and to propagate throughout the plant and between individual plants. Plants in turn have developed antiviral defence mechanisms that must be counteracted by viral factors. These factors appear to be preferred targets for alternative plant defences. In our laboratory, we try to understand this complex interplay, mainly in the infection of the potyvirus Plum pox virus (PPV), the causal agent of sharka, a damaging disease of Prunus trees. We are especially interested in defence responses related to RNA silencing and its viral suppressors.
Publications
Pasin F, Bedoya LC, Bernabé-Orts JM, Gallo A, Simón-Mateo C, Orzaez D, García JA. Multiple T-DNA delivery to plants using novel mini binary vectors with compatible replication origins. ACS Synth Biol 2017 Oct 20;6(10):1962-1968
Gallo A, Valli A, Calvo M, García JA. A functional link between RNA replication and virion assembly in the potyvirus Plum pox virus. J. Virol. 2018; 92, e02179-17.
Ochoa J, Valli A, Martín-Trillo M, Simón-Mateo C, García JA, Rodamilans B. Sterol isomerase HYDRA1 interacts with RNA silencing suppressor P1b and restricts potyviral infection. Plant Cell Environ 2019; 42: 3015-3026
Hervás M, Navajas R, Chagoyen M, Garcia JA, Martinez-Turiño, S. Phosphorylation-related cross-talk between distant regions of the core region of the coat protein contributes to virion assembly of Plum pox virus. . Mol Plant Microbe Interact 2020; 33: 653-667
González de Prádena A, Sánchez Jiménez A, San León D, Simmonds P, García JA, Valli AA. Plant virus genome is shaped by specific dinucleotide restrictions that influence viral infection. MBio 2020; 11: e02818-02819
A complex plant-virus interactive network modulates infectivity and symptom severity. Most plant viruses cannot infect all their potential hosts, and when they do, serious illness is not the norm, as revealed by recent metagenomic studies. Our laboratory studies this interaction network, which facilitates virus replication and propagation, but also induces plant defense responses and disease symptoms. Plum pox virus, our main subject of study, belongs to the family Potyviridae, the largest group of plant RNA viruses and causes sharka, a serious disease of stone fruit trees.
We are especially interested in defense responses related to RNA silencing and its viral suppressors. The typical silencing suppressor of potyvirids is HCPro, but the existence of additional silencing suppressors in different potyvirids, prompted us to suggest that escaping RNA silencing-mediated antiviral defenses is a powerful driving force of virus evolution. Potyvirid genomic RNAs are expressed through the synthesis of large polyproteins, processed by viral-encoded endopeptidases.
We are studying how host-specific modulation of this processing can contribute to potyviral pathogenicity and host range definition. Encapsidation of potyvirid genome is an active process. We have demonstrated a functional link between potyvirus RNA replication and virion assembly, and we are studying how posttranslational modifications of the capsid protein can contribute to sort the potyviral RNA into translation, replication or encapsidation. An important goal of our laboratory is applying our basic research results to control viral diseases through novel strategies. For instance, we are attenuating plant viruses by recoding their genomes in order to use them as cross-protection agents. We are also interested in developing other valuable biotools, such as a novel T-DNA delivery system, which can be used to efficiently inoculate plants with infectious viral cDNA clones, among other multiple applications.
Laboratory Members
Adrian A. Valli
Ramón y Cajal grant call: 2018
Project´s name: Plant-Virus Coevolution
Summary: With a world population estimated in 9.6 billion people by mid-century, there is a pressing need to improve food security, with crop protection measures being essential components of any strategy that aims to reduce yield losses. RNA viruses are among the most abundant and economically relevant pathogens infecting plants; indeed, they cause more than 50% of viral crop damage worldwide. Gaining insight about this group of viruses is then critical to reveal and understand not only new features of them, but also to discover novel plant protein networks acting as defensive barriers. Thanks to these basic studies, more and better antiviral strategies are being developed and implemented for the protection of important crops. Intriguingly, despite the importance of plant RNA viruses for food security, it is surprising to find that very little is known about their RNA-dependent RNA polymerases (RdRPs), putative RdRP protein partners and the precise role/s of these partners during infection.
As a relevant socio-economical case we currently study the partnership between RdRP and the pyrophosphatase HAM1 deriving from Ugandan cassava brown streak virus, one the agents causing the “Ebola of plants” in cassava (the fourth most important crop on earth based on calorie intake). To do that we follow a multidisciplinary approach that includes (i) synthetic biology to build chimerical infectious clones, (ii) genomics studies of virus mutants to define quasispecies variability, (iii) structural studies by cryo-electron microscopy to define protein 3D structures, (iv) metabolomics studies by HPLC-MS/MS to understand the viral disease, and (v) viral ecology to decipher the interaction between cassava (and other plants from the Euphorbiaceae family) and viruses in nature. These approaches will greatly help us to fill gaps in our understanding of RdRPs in general, as well as RdRP-HAM1 partnership in viruses infecting plants from the Euphorbiaceae family.
Figure Legend: Infection of plants with laboratory-designed cDNA clones of UCBSV. (A) The RNA genome of UCBSV was retrotranscribed to cDNA and this sequence was then inserted in between a strong promoter (p35S from Cauliflower mosaic virus) and a terminator (tNOS from Agrobacterium nopaline synthase) to generate the infectious cDNA plasmid termed pLX-UCBSV (Pasin et al., 2017, ACS Synthetic Biology). This plasmid was further modified to tag the virus with GFP, thus generating pLX-UCBSV-GFP. (B) Leaves of cassava plants (Manihot esculenta) at 2 months post-inoculation observed under white light (bar = 4 cm). Symptoms of infection are clearly detected in upper leaves of plants inoculated with pLX-UCBSV. (C) One leaf of a Nicotiana benthamiana plant, infected with UCBSV-GFP, observed under white light and UV light (to detect GFP-derived fluorescence) with a stereomicroscope. GFP is distributed across primary and secondary veins as the virus spread through the leaf (bar = 0.5 cm).
Laboratory Members
Funding
Uncovering the mechanism and potential uses of viral RNA polymerase slippage. Spanish MICINN (BIO2015-73900-JIN), from 2017 to 2019 (3 years).
Ramón y Cajal Program (RYC2018-025523-I). Spanish MICINN, from 2020 to 2024 (5 years)..
The paradigm of Euphorbiaceous-Virus interaction: a multidisciplinary approach to develop novel antiviral strategies in plants. Spanish MICINN (PID2019-110979RB-I00), from 2020 to 2022 (3 years).
The Euphorbiaceous-Virus Coevolution. Spanish Research Council (CSIC), from 2020 to 2022 (3 years).
