María Teresa Serra

Bio: María Teresa Serra is an academic researcher from Spanish National Research Council. The author has contributed to research in topics: Pepper mild mottle virus & Tobamovirus. The author has an hindex of 17, co-authored 25 publications receiving 1048 citations.

Nucleotide sequence of the genomic RNA of pepper mild mottle virus, a resistance-breaking tobamovirus in pepper

Abstract: The entire genomic RNA of a Spanish isolate of pepper mild mottle virus (PMMV-S), a resistance-breaking virus in pepper, was cloned and sequenced and shown to be similar to other tobamoviruses in its genomic organization. It consisted of 6357 nucleotides (nt) and contained four open reading frames (ORFs) which encode a 126K protein and a readthrough 183K protein (nt 70 to 4908), a 28K protein (nt 4909 to 5682) and a 17.5K coat protein (nt 5685 to 6158). This is the first tobamovirus in which none of the ORFs overlap. Both its nucleic acid and predicted protein sequences were compared with the previously determined sequences of other tobamoviruses. The variations and similarities found and their relationship with the pathogenicity of this virus are discussed.

Proteomic analysis of pathogenesis-related proteins (PRs) induced by compatible and incompatible interactions of pepper mild mottle virus (PMMoV) in Capsicum chinense L3 plants

Abstract: Resistance conferred by the L(3) gene is active against most of the tobamoviruses, including the Spanish strain (PMMoV-S), a P(1,2) pathotype, but not against certain strains of pepper mild mottle virus (PMMoV), termed P(1,2,3) pathotype, such as the Italian strain (PMMoV-I). Both viruses are nearly identical at their nucleotide sequence level (98%) and were used to challenge Capsicum chinense PI159236 plants harbouring the L(3) gene in order to carry out a comparative proteomic analysis of PR proteins induced in this host in response to infection by either PMMoV-S or PMMoV-I. PMMoV-S induces a hypersensitive reaction (HR) in C. chinense PI159236 plant leaves with the formation of necrotic local lesions and restriction of the virus at the primary infection sites. In this paper, C. chinense PR protein isoforms belonging to the PR-1, beta-1,3-glucanases (PR-2), chitinases (PR-3), osmotin-like protein (PR-5), peroxidases (PR-9), germin-like protein (PR-16), and PRp27 (PR-17) have been identified. Three of these PR protein isoforms were specifically induced during PMMoV-S-activation of C. chinense L(3) gene-mediated resistance: an acidic beta-1,3-glucanase isoform (PR-2) (M(r) 44.6; pI 5.1), an osmotin-like protein (PR-5) (M(r) 26.8; pI 7.5), and a basic PR-1 protein isoform (M(r) 18; pI 9.4-10.0). In addition, evidence is presented for a differential accumulation of C. chinense PR proteins and mRNAs in the compatible (PMMoV-I)-C. chinense and incompatible (PMMoV-S)-C. chinense interactions for proteins belonging to all PR proteins detected. Except for an acidic chitinase (PR-3) (M(r) 30.2; pI 5.0), an earlier and higher accumulation of PR proteins and mRNAs was detected in plants associated with HR induction. Furthermore, the accumulation rates of PR proteins and mRNA did not correlate with maximal accumulation levels of viral RNA, thus indicating that PR protein expression may reflect the physiological status of the plant.

The 3a protein from cucumber mosaic virus increases the gating capacity of plasmodesmata in transgenic tobacco plants.

Abstract: The 3a protein, encoded by RNA 3 of cucumber mosaic virus (CMV), is the putative movement protein of viral progeny in infected plants. An analysis of transgenic tobacco plants constitutively expressing the CMV 3a protein showed that the protein is accumulated in leaves at every stage of development. In fully expanded leaves the protein is immunodetectable mostly in a cell-wall-enriched fraction. Dye-coupling experiments using fluorescent-dextran probes were performed on fully expanded leaves to study the modifying effect of CMV 3a protein on the gating capacity of plasmodesmata. Movement of fluorescein-isothiocyanate-labelled dextran with a mean molecular mass of 10000 Da, and an approximate Stokes' radius of 2.3 nm, was detected between cells of the 3a protein transgenic plants, but not in the control plants. These results are consistent with the idea that the CMV 3a protein is involved in the modification of plasmodesmata and, therefore, in the cell-to-cell spread of the virus.

The coat protein is required for the elicitation of the Capsicum L2 gene-mediated resistance against the tobamoviruses.

Abstract: In Capsicum, the resistance against tobamoviruses conferred by the L2 gene is effective against all but one of the known tobamoviruses. Pepper mild mottle virus (PMMoV) is the only virus which escapes its action. To identify the viral factors affecting induction of the hypersensitive reaction (HR) mediated by the Capsicum spp. L2 resistance gene, we have constructed chimeric viral genomes between paprika mild mottle virus (PaMMV) (a virus able to induce the HR) and PMMoV. A hybrid virus with the PaMMV coat protein gene substituted in the PMMoV-S sequences was able to elicit the HR in Capsicum frutescens (L2L2) plants. These data indicate that the sequences that affect induction of the HR mediated by the L2 resistance gene reside in the coat protein gene. Furthermore, a mutant that codes for a truncated coat protein was able to systemically spread in these plants. Thus, the elicitation of the host response requires the coat protein and not the RNA.

Initiation and Maintenance of Virus-Induced Gene Silencing

Abstract: The phytoene desaturase (PDS) gene of Nicotiana benthamiana was silenced in plants infected with potato virus X (PVX) vectors carrying PDS inserts, and a green fluorescent protein (GFP) transgene was silenced in plants infected with PVX–GFP. This virus-induced gene silencing (VIGS) is post-transcriptional and cytoplasmic because it is targeted against exons rather than introns of PDS RNA and against viral RNAs. Although PDS and GFP RNAs are most likely targeted through the same mechanism, the VIGS phenotypes differed in two respects. PDS mRNA was targeted by VIGS in all green tissue of the PVX–PDS—infected plant, whereas PVX–PDS was not affected. In contrast, VIGS of the GFP was targeted against PVX–GFP. Initially, VIGS of the GFP was initiated in all green tissues, as occurred with PDS VIGS. However, after 30 days of infection, the GFP VIGS was no longer initiated in newly emerging leaves, although it was maintained in tissue in which it had already been initiated. Based on these analyses, we propose a model for VIGS in which the initiation of VIGS is dependent on the virus and maintenance of it is virus independent.

Cell-to-Cell and Long-Distance Transport of Viruses in Plants.

Abstract: The idea that viruses move through plants in two distinct modes was accurately concluded by G. Samuel in a 1934 paper describing the transport of tobacco mosaic virus (TMV) through solanaceous hosts: “lt is considered that these facts favour the theory of a slow cell to cell movement of the virus via the plasmodesmen, combined with a rapid distribution through the plant via the phloem” (Samuel, 1934). It is now firmly established that plant viruses move from cell to cell and over long distances by exploiting and modifying preexisting pathways for macromolecular movement within cells, between cells, and between organs. In this review, we focus on the roles of vira1 and host components in the movement of viruses through these pathways. Exhaustive coverage of all aspects of movement is not possible, but the reader is referred to several excellent reviews that emphasize various facets of shortand long-range virus transport (Atabekov and Taliansky, 1990; Maule, 1991; Deom et al., 1992; Citovsky, 1993; Leisner and Turgeon, 1993; Lucas and Gilbertson, 1994; Lucas, 1995).

Development of broad virus resistance in non-transgenic cucumber using CRISPR/Cas9 technology.

Abstract: Genome editing in plants has been boosted tremendously by the development of CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats) technology. This powerful tool allows substantial improvement in plant traits in addition to those provided by classical breeding. Here, we demonstrate the development of virus resistance in cucumber (Cucumis sativus L.) using Cas9/subgenomic RNA (sgRNA) technology to disrupt the function of the recessive eIF4E (eukaryotic translation initiation factor 4E) gene. Cas9/sgRNA constructs were targeted to the N' and C' termini of the eIF4E gene. Small deletions and single nucleotide polymorphisms (SNPs) were observed in the eIF4E gene targeted sites of transformed T1 generation cucumber plants, but not in putative off-target sites. Non-transgenic heterozygous eif4e mutant plants were selected for the production of non-transgenic homozygous T3 generation plants. Homozygous T3 progeny following Cas9/sgRNA that had been targeted to both eif4e sites exhibited immunity to Cucumber vein yellowing virus (Ipomovirus) infection and resistance to the potyviruses Zucchini yellow mosaic virus and Papaya ring spot mosaic virus-W. In contrast, heterozygous mutant and non-mutant plants were highly susceptible to these viruses. For the first time, virus resistance has been developed in cucumber, non-transgenically, not visibly affecting plant development and without long-term backcrossing, via a new technology that can be expected to be applicable to a wide range of crop plants.

Mechanisms of Pathogen-Derived Resistance to Viruses in Transgenic Plants.

Abstract: lhe Sainsbury Laboratory, John lnnes Centre, Colney, Norwich NR4 7UH, United Kingdom INTRODUCTION In 1985, Sanford and Johnston developed the simple and ele- gant concept of parasite- or pathogen-derived resistance (Sanford and Johnston, 1985). Subsequently, there have been numerous attempts to generate virus resistance in transgenic plants based on this concept through the expression of virus- derived genes or genome fragments (Beachy, 1993; Wilson, 1993; Baulcombe, 1994b; Lomonossoff, 1995). Many of these attempts have been successful, and some have led to the de- velopment of virus-resistant potato and squash cultivars for commercial application. In this article, the major emphasis is on the mechanisms of pathogen-derived resistance rather than on the practicali- ties of using this technology for crop improvement. These mechanisms have proven difficult to unravel largely because a resistance mechanism related to transgene silencing can override the direct phenotype of virus-derived transgenes. lhe examples discussed first are those in which it is clear whether the mechanism involves gene silencing. In later sections, some less well understood examples are reviewed. The final sec- tion anticipates likely future developments in pathogen-derived resistance.

Genetics of Plant Virus Resistance

Abstract: Genetic resistance to plant viruses has been used for at least 80 years to control agricultural losses to viral diseases. To date, hundreds of naturally occurring genes for resistance to plant viruses have been reported from studies of both monocot and dicot crops, their wild relatives, and the plant model, Arabidopsis. The isolation and characterization of a few of these genes in the past decade have resulted in detailed knowledge of some of the molecules that are critical in determining the outcome of plant viral infection. In this chapter, we have catalogued genes for resistance to plant viruses and have summarized current knowledge regarding their identity and inheritance. Insofar as information is available, the genetic context, genomic organization, mechanisms of resistance and agricultural deployment of plant virus resistance genes are also discussed.