Tobamovirus

About: Tobamovirus is a research topic. Over the lifetime, 1285 publications have been published within this topic receiving 54248 citations.

Salicylic acid : a likely endogenous signal in the resistance response of tobacco to viral infection

Abstract: Some cultivars of tobacco are resistant to tobacco mosaic virus (TMV) and synthesize pathogenesis-related (PR) proteins upon infection. In a search for the signal or signals that induce resistance or PR genes, it was found that the endogenous salicylic acid levels in resistant, but not susceptible, cultivars increased at least 20-fold in infected leaves and 5-fold in uninfected leaves after TMV inoculation. Induction of PRl genes paralleled the rise in salicylic acid levels. Since earlier work has demonstrated that treatment with exogenous salicylic acid induces PR genes and resistance, these findings suggest that salicylic acid functions as the natural transduction signal.

Delay of disease development in transgenic plants that express the tobacco mosaic virus coat protein gene.

Abstract: A chimeric gene containing a cloned cDNA of the coat protein (CP) gene of tobacco mosaic virus (TMV) was introduced into tobacco cells on a Ti plasmid of Agrobacterium tumefaciens from which tumor inducing genes had been removed. Plants regenerated from transformed cells expressed TMV mRNA and CP as a nuclear trait. Seedlings from self-fertilized transgenic plants were inoculated with TMV and observed for development of disease symptoms. The seedlings that expressed the CP gene were delayed in symptom development and 10 to 60 percent of the transgenic plants failed to develop symptoms for the duration of the experiments. Increasing the concentration of TMV in the inoculum shortened the delay in appearance of symptoms. The results of these experiments indicate that plants can be genetically transformed for resistance to virus disease development.

Tobacco Rar1, EDS1 and NPR1/NIM1 like genes are required for N‐mediated resistance to tobacco mosaic virus

Abstract: The tobacco N gene confers resistance to tobacco mosaic virus (TMV) and encodes a Toll-interleukin-1 receptor/nucleotide binding site/leucine-rich repeat (TIR-NBS-LRR) class protein. We have developed and used a tobacco rattle virus (TRV) based virus induced gene silencing (VIGS) system to investigate the role of tobacco candidate genes in the N-mediated signalling pathway. To accomplish this we generated transgenic Nicotiana benthamiana containing the tobacco N gene. The transgenic lines exhibit hypersensitive response (HR) to TMV and restrict virus spread to the inoculated site. This demonstrates that the tobacco N gene can confer resistance to TMV in heterologous N. benthamiana. We have used this line to study the role of tobacco Rar1-, EDS1-, and NPR1/NIM1- like genes in N-mediated resistance to TMV using a TRV based VIGS approach. Our VIGS analysis suggests that these genes are required for N function. EDS1-like gene requirement for the N function suggests that EDS1 could be a common component of bacterial, fungal and viral resistance signalling mediated by the TIR-NBS-LRR class of resistance proteins. Requirement of Rar1- like gene for N-mediated resistance to TMV and some powdery mildew resistance genes in barley provide the first example of converging points in the disease resistance signalling pathways mediated by TIR-NBS-LRR and CC-NBS-LRR proteins. The TRV based VIGS approach as described here to study N-mediated resistance signalling will be useful for the analysis of not only disease resistance signalling pathways but also of other signalling pathways in genetically intractable plant systems.

Biological function of pathogenesis-related proteins: Four tobacco pathogenesis-related proteins are chitinases.

Abstract: Four endochitinases (poly[1,4-(N-acetyl-β-D-glucosaminide)] glycanohydrolase, EC 3.2.1.14) have been purified from leaves of Nicotiana tabacum cv. Samsun NN reacting hypersensitively to tobacco mosaic virus. Two of them are acidic proteins of molecular weights 27,500 and 28,500 and have been identified as 2 of the 10 pathogenesis-related proteins that are known to accumulate in tobacco in response to stress or pathogen attack. These two pathogenesis-related proteins, named “P” and “Q” when their biological function was unknown, account for one-third of tobacco mosaic virus-induced chitinase activity of tobacco leaves. They are serologically closely related to the two other chitinases, which can be considered as new basic pathogenesis-related proteins. These two basic chitinases exhibit higher molecular weights (32,000 and 34,000) and higher specific enzyme activity than the two acidic isoforms.

Brassinosteroid functions in a broad range of disease resistance in tobacco and rice.

Abstract: Summary Brassinolide (BL), considered to be the most important brassinosteroid (BR) and playing pivotal roles in the hormonal regulation of plant growth and development, was found to induce disease resistance in plants. To study the potentialities of BL activity on stress responding systems, we analyzed its ability to induce disease resistance in tobacco and rice plants. Wild-type tobacco treated with BL exhibited enhanced resistance to the viral pathogen tobacco mosaic virus (TMV), the bacterial pathogen Pseudomonas syringae pv. tabaci (Pst), and the fungal pathogen Oidium sp. The measurement of salicylic acid (SA) in wild-type plants treated with BL and the pathogen infection assays using NahG transgenic plants indicate that BL-induced resistance does not require SA biosynthesis. BL treatment did not induce either acidic or basic pathogenesis-related (PR) gene expression, suggesting that BL-induced resistance is distinct from systemic acquired resistance (SAR) and wound-inducible disease resistance. Analysis using brassinazole 2001, a specific inhibitor for BR biosynthesis, and the measurement of BRs in TMV-infected tobacco leaves indicate that steroid hormone-mediated disease resistance (BDR) plays part in defense response in tobacco. Simultaneous activation of SAR and BDR by SAR inducers and BL, respectively, exhibited additive protective effects against TMV and Pst, indicating that there is no cross-talk between SAR- and BDR-signaling pathway downstream of BL. In addition to the enhanced resistance to a broad range of diseases in tobacco, BL induced resistance in rice to rice blast and bacterial blight diseases caused by Magnaporthe grisea and Xanthomonas oryzae pv. oryzae, respectively. Our data suggest that BDR functions in the innate immunity system of higher plants including dicotyledonous and monocotyledonous species.