scholarly journals Comparative analysis identifies amino acids critical for citrus tristeza virus (T36CA) encoded proteins involved in suppression of RNA silencing and differential systemic infection in two plant species

2020 ◽  
Vol 22 (1) ◽  
pp. 64-76
Author(s):  
Angel Y. S. Chen ◽  
James H. C. Peng ◽  
MaryLou Polek ◽  
Tongyan Tian ◽  
Márta Ludman ◽  
...  
Keyword(s):  
Amino Acids ◽  
Comparative Analysis ◽  
Plant Species ◽  
Rna Silencing ◽  
Citrus Tristeza Virus ◽  
Systemic Infection ◽  
Encoded Proteins ◽  
Tristeza Virus ◽  
Citrus Tristeza

scholarly journals Citrus tristeza virus p23: Determinants for Nucleolar Localization and Their Influence on Suppression of RNA Silencing and Pathogenesis

2013 ◽  
Vol 26 (3) ◽  
pp. 306-318 ◽  
Author(s):  
Susana Ruiz-Ruiz ◽  
Nuria Soler ◽  
Jesús Sánchez-Navarro ◽  
Carmen Fagoaga ◽  
Carmelo López ◽  
...  
Keyword(s):  
Amino Acids ◽  
Rna Silencing ◽  
Citrus Tristeza Virus ◽  
Ectopic Expression ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Nucleolar Localization ◽  
Deletion Mutants ◽  
Tristeza Virus ◽  
Citrus Tristeza

Citrus tristeza virus (CTV) encodes a singular protein (p23, 209 amino acids) with multiple functions, including RNA silencing suppression (RSS). Confocal laser-scanning microscopy of green fluorescent protein (GFP)-p23 agroexpressed in Nicotiana benthamiana revealed its accumulation in the nucleolus, Cajal bodies, and plasmodesmata. To dissect the nucleolar localization signal (NoLS) typically associated with basic motifs, seven truncated and 10 point-mutated versions of p23 were assayed. Deletion mutants showed that regions 50 to 86 and 100 to 157 (excluding fragment 106 to 114), both with basic motifs and the first with a zinc-finger, contain the (bipartite) NoLS. Alanine substitutions delimited this signal to three cysteines of the Zn-finger and some basic amino acids. RSS activity of p23 in N. benthamiana was abolished by essentially all mutants, indicating that it involves most p23 regions. The necrotic-inducing ability of p23 when launched in N. benthamiana from Potato virus X was only retained by deletion mutant 158-209 and one substitution mutant, showing that the Zn-finger and flanking basic motifs form part of the pathogenic determinant. Ectopic expression of p23 and some deletion mutants in transgenic Mexican lime demarcated a similar determinant, suggesting that p23 affects related pathways in citrus and N. benthamiana. Both RSS activity and pathogenicity of p23 appear related to its nucleolar localization.

scholarly journals Identification of Key Residues Required for RNA Silencing Suppressor Activity of p23 Protein from a Mild Strain of Citrus Tristeza Virus

Viruses ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 782 ◽  
Author(s):  
Zhuoran Li ◽  
Yizhong He ◽  
Tao Luo ◽  
Xi Zhang ◽  
Haoliang Wan ◽  
...  
Keyword(s):  
Rna Silencing ◽  
Citrus Tristeza Virus ◽  
Silencing Suppressor ◽  
Mild Strain ◽  
High Sequence Identity ◽  
Suppressor Activity ◽  
Protein Levels ◽  
Tristeza Virus ◽  
Citrus Tristeza ◽  
Citrus Trees

The severe strain of citrus tristeza virus (CTV) causes quick decline of citrus trees. However, the CTV mild strain causes no symptoms and commonly presents in citrus trees. Viral suppressor of RNA silencing (VSR) plays an important role in the successful invasion of viruses into plants. For CTV, VSR has mostly been studied in severe strains. In this study, the N4 mild strain in China was sequenced and found to have high sequence identity with the T30 strain. Furthermore, we verified the functions of three VSRs in the N4 strain, and p23 was found to be the most effective in terms of local silencing suppressor activity among the three CTV VSRs and localized to both nucleus and plasmodesmata, which is similar to CTV T36 strain. Several conserved amino acids were identified in p23. Mutation of E95A/V96A and M99A/L100AA impaired p23 protein stability. Consequently, these two mutants lost most of its suppressor activity and their protein levels could not be rescued by co-expressing p19. Q93A and R143A/E144A abolished p23 suppressor activity only and their protein levels increased to wild type level when co-expressed with p19. This work may facilitate a better understanding of the pathogenic mechanism of CTV mild strains.

scholarly journals Agroinoculation of Citrus tristeza virus Causes Systemic Infection and Symptoms in the Presumed Nonhost Nicotiana benthamiana

2011 ◽  
Vol 24 (10) ◽  
pp. 1119-1131 ◽  
Author(s):  
Silvia Ambrós ◽  
Choaa El-Mohtar ◽  
Susana Ruiz-Ruiz ◽  
Leandro Peña ◽  
José Guerri ◽  
...  
Keyword(s):  
Nicotiana Benthamiana ◽  
Time Course ◽  
Citrus Tristeza Virus ◽  
Systemic Infection ◽  
Genetic System ◽  
Herbaceous Host ◽  
System A ◽  
Tristeza Virus ◽  
Efficient Transmission ◽  
Citrus Tristeza

Citrus tristeza virus (CTV) naturally infects only some citrus species and relatives and within these it only invades phloem tissues. Failure to agroinfect citrus plants and the lack of an experimental herbaceous host hindered development of a workable genetic system. A full-genome cDNA of CTV isolate T36 was cloned in binary plasmids and was used to agroinfiltrate Nicotiana benthamiana leaves, with or without coinfiltration with plasmids expressing different silencing-suppressor proteins. A time course analysis in agroinfiltrated leaves indicated that CTV accumulates and moves cell-to-cell for at least three weeks postinoculation (wpi), and then, it moves systemically and infects the upper leaves with symptom expression. Silencing suppressors expedited systemic infection and often increased infectivity. In systemically infected Nicotiana benthamiana plants, CTV invaded first the phloem, but after 7 wpi, it was also found in other tissues and reached a high viral titer in upper leaves, thus allowing efficient transmission to citrus by stem-slash inoculation. Infected citrus plants showed the symptoms, virion morphology, and phloem restriction characteristic of the wild T36 isolate. Therefore, agroinfiltration of Nicotiana benthamiana provided the first experimental herbaceous host for CTV and an easy and efficient genetic system for this closterovirus.

Citrus tristeza virus: Host RNA Silencing and Virus Counteraction

2019 ◽  
pp. 195-207 ◽  
Author(s):  
Susana Ruiz-Ruiz ◽  
Beatriz Navarro ◽  
Leandro Peña ◽  
Luis Navarro ◽  
Pedro Moreno ◽  
...  
Keyword(s):  
Rna Silencing ◽  
Citrus Tristeza Virus ◽  
Tristeza Virus ◽  
Citrus Tristeza

scholarly journals Citrus Tristeza Virus: Survival at the Edge of the Movement Continuum

2008 ◽  
Vol 82 (13) ◽  
pp. 6546-6556 ◽  
Author(s):  
Svetlana Y. Folimonova ◽  
Alexey S. Folimonov ◽  
Satyanarayana Tatineni ◽  
William O. Dawson
Keyword(s):  
Citrus Tristeza Virus ◽  
Cell Movement ◽  
Systemic Infection ◽  
Sour Orange ◽  
Citrus Species ◽  
Long Distance ◽  
Susceptible Host ◽  
Long Distance Movement ◽  
Tristeza Virus ◽  
Citrus Tristeza

ABSTRACT Systemic invasion of plants by viruses is thought to involve two processes: cell-to-cell movement between adjacent cells and long-distance movement that allows the virus to rapidly move through sieve elements and unload at the growing parts of the plant. There is a continuum of proportions of these processes that determines the degrees of systemic infection of different plants by different viruses. We examined the systemic distribution of Citrus tristeza virus (CTV) in citrus species with a range of susceptibilities. By using a “pure” culture of CTV from a cDNA clone and green fluorescent protein-labeled virus we show that both cell-to-cell and long-distance movement are unusually limited, and the degree of limitation varies depending on the citrus host. In the more-susceptible hosts CTV infected only a small portion of phloem-associated cells, and moreover, the number of infection sites in less-susceptible citrus species was substantially decreased further, indicating that long-distance movement was reduced in those hosts. Analysis of infection foci in the two most differential citrus species, Citrus macrophylla and sour orange, revealed that in the more-susceptible host the infection foci were composed of a cluster of multiple cells, while in the less-susceptible host infection foci were usually single cells, suggesting that essentially no cell-to-cell movement occurred in the latter host. Thus, CTV in sour orange represents a pattern of systemic infection in which the virus appears to function with only the long-distance movement mechanism, yet is able to survive in nature.

scholarly journals Chimeric cDNA Sequences from Citrus tristeza virus Confer RNA Silencing-Mediated Resistance in Transgenic Nicotiana benthamiana Plants

2006 ◽  
Vol 96 (8) ◽  
pp. 819-827 ◽  
Author(s):  
Gourgopal Roy ◽  
Mysore R. Sudarshana ◽  
Diane E. Ullman ◽  
Shou-Wei Ding ◽  
Abhaya M. Dandekar ◽  
...  
Keyword(s):  
Nicotiana Benthamiana ◽  
Rna Silencing ◽  
Citrus Tristeza Virus ◽  
Potato Virus X ◽  
Northern Hybridization ◽  
Transcriptional Gene Silencing ◽  
Small Interfering Rnas ◽  
Cdna Sequences ◽  
Tristeza Virus ◽  
Citrus Tristeza

RNA silencing has been shown to be an important mechanism for conferring resistance in transgenic, virus-resistant plants. We used this approach to evaluate resistance in Nicotiana benthamiana plants transformed with chimeric coding and noncoding sequences from Citrus tristeza virus (CTV). Several independent transgenic plant lines were generated, using two constructs (pCTV1 and pCTV2) designed to produce self-complementary transcripts. The pCTV1 contained cDNA sequences from the CTV capsid protein (CP), p20, and 3′ untranslated region (UTR); and pCTV2 contained CP, p23, and 3′ UTR sequences. Heterologous recombinant Potato virus X (PVX) containing either homologous or heterologous CTV sequences was used to challenge plants and resistance was evaluated phenotypically and validated with reverse-transcriptase polymerase chain reaction and northern hybridization analysis. Transgenic plants (T1 generation) for each construct showed resistance to recombinant PVX constructs used for challenge experiments when PVX contained p20 or UTR (for CTV1 plants), or p23 or UTR (for CTV2 plants). However, no resistance was seen when plants were challenged with PVX containing the CTV CP. T2 generation plants also showed resistance even when challenged with PVX containing the cognate CTV sequences obtained from heterologous CTV isolates. The presence of transgene-specific small interfering RNAs in the resistant CTV1 and CTV2 plants indicated that resistance was mediated by post-transcriptional gene silencing.

Comparing p20’s RNA silencing suppressing activity among five phylogenetic groups of Citrus Tristeza virus

2012 ◽  
Vol 133 (1) ◽  
pp. 229-235 ◽  
Author(s):  
Natália T. Marques ◽  
Ângela A. Costa ◽  
Débora Lopes ◽  
Gonçalo Silva ◽  
Gustavo Nolasco
Keyword(s):  
Rna Silencing ◽  
Citrus Tristeza Virus ◽  
Phylogenetic Groups ◽  
Tristeza Virus ◽  
Citrus Tristeza

First report of citrus tristeza virus in commercial citrus orchards in Tunisia

2021 ◽  
Author(s):  
Asma Najar ◽  
Imen Hamdi ◽  
Souad Mahmoud ◽  
Lassaad Medhioub ◽  
Imed Jaouadi ◽  
...  
Keyword(s):  
Citrus Tristeza Virus ◽  
First Report ◽  
Citrus Orchards ◽  
Tristeza Virus ◽  
Citrus Tristeza
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