21 Questions
Statement
Viral diseases cause significant damage to crop yield and quality. While fungi- and bacteria-induced diseases can be controlled by pesticides, no effective approaches are available to control viruses with chemicals as they use the cellular functions of their host for their infection cycle. The conventional method of viral disease control is to use the inherent resistance of plants through breeding. However, the genetic sources of viral resistance are often limited. Recently, genome editing technology enabled the publication of multiple attempts to artificially induce new resistance types by manipulating host factors necessary for viral infection.
Plants are affected by various abiotic and biotic factors, including ______, which cause yield loss and estimated to cost over $30 billion annually.
viruses
Viruses depend on ______ cell machinery for survival, altering ______ gene expression to suit their needs.
host
Remarkable progress has been made in understanding plant-virus interactions at the molecular level, enabling the disruption of host factors necessary for viral infection leading to ______.
resistance
Virus resistance ______ in plants include R gene-mediated resistance, recessive resistance, and antiviral RNA silencing.
mechanisms
Plants show ______ when a pathogen suppresses PTI response and produces pathogenic effectors.
susceptibility
EIF4E and eIF(iso)4E in Arabidopsis thaliana are involved in ______ infection, with ClYVV using eIF4E and TuMV using eIF(iso)4E.
potyvirus
NCBP, another ______ isoform, has recently been identified as a susceptible factor for viral infection.
eIF4E
Simultaneous CRISPR/Cas9-mediated genome editing of two ______s genes reduces the susceptibility to viruses in cassava and reduces the severity of symptoms.
nCBP
Pot1, a natural ______ allele isolated from a wild tomato relative, exhibits a wider resistance spectrum against potato virus Y and tobacco etch virus strains than the corresponding null allele.
eIF4E1
1INS, a ______, is considered a null allele and confers resistance to the N strain of potato virus.
frameshift
Understanding the viral infection cycle in detail is essential for conferring virus resistance by ______ host factors, as some viruses use unusual host factors.
manipulating
The receptor-like kinase BAM1, located at ______ to facilitate the systemic spread of RNA silencing in A. thaliana, is also a target protein of C4, an RNA silencing suppressor of tomato yellow leaf curl virus.
plasmodesmata
Autophagy, a cellular process involved in both antiviral and proviral mechanisms, has been recently reported to be involved in plant responses against ______.
pathogens
Phytohormones such as SA, JA, ethylene, and abscisic acid regulate plant responses against pathogens, with SA triggering the defense response against viruses and inducing systemic resistance in ______ tissues.
distal
The possibility of ______ new virus-resistant crops by specifically manipulating host factors based on a good understanding of their functions is an exciting prospect.
producing
RNA silencing is a major antiviral ______ in plants, resulting in the degradation of viral genome at the infection site.
mechanism
The HR ______ is associated with the activation and expression of various molecular events such as salicylic acid (SA), jasmonic acid (JA), mitogen-activated protein kinase signaling, calcium ion influx, callose deposition, membrane permeability modification, and the expression of pathogenesis-related (PR) proteins and reactive oxygen species (ROS) and nitric oxide (NO).
response
RNA silencing is a ______ plant counter-defense against virus-derived double-stranded (ds) RNA, which is the most common defense mechanism against viruses.
host
RNA silencing is a powerful defense ______ that can be used to develop transgenic virus resistance.
mechanism
The coat protein (CP)-mediated transgenic papaya ______ against papaya ringspot virus through RNA silencing is a successful application of this technology.
resistance
Study Notes
- Recessive resistance against plant viruses is often due to modifications in specific genes encoding host factors essential for viral infection. Some examples are eIF4E, eIF4G, and their isoforms.
- RNA silencing is a major antiviral mechanism in plants, resulting in the degradation of viral genome at the infection site.
- Additional viral resistance mechanisms include those related to ubiquitin–proteasome machinery, autophagy, and DNA methylation.
- R genes, encoded by host plants, trigger race-specific resistance in response to Avr genes of pathogens, leading to the HR response which is a form of programmed cell death that halts viral invasion.
- The HR response is associated with the activation and expression of various molecular events such as salicylic acid (SA), jasmonic acid (JA), mitogen-activated protein kinase signaling, calcium ion influx, callose deposition, membrane permeability modification, and the expression of pathogenesis-related (PR) proteins and reactive oxygen species (ROS) and nitric oxide (NO).
- The R genes encode nucleotide-binding (NB) and leucine-rich-repeat (LRR) domains, while Avr proteins do not share any common structure.
- RNA silencing is a host plant counter-defense against virus-derived double-stranded (ds) RNA, which is the most common defense mechanism against viruses.
- Viral dsRNA is cleaved by Dicer-like (DCL) enzymes to generate virus-induced small RNAs (vsRNAs) that guide Argonaute (AGO) proteins to targeted RNA for degradation.
- Viral resistance can also be achieved by manipulating host susceptible factors for virus infection. Since viruses are intracellular parasites, they rely on host cellular mechanisms for their survival.
- Exogenous applications of viral dsRNA and siRNA for disease protection are possible based on the understanding of the RNA silencing mechanisms.
- Coat protein (CP)-mediated transgenic papaya resistance against papaya ringspot virus through RNA silencing is a successful application of this technology.
- RNA silencing is an effective defense mechanism against viral RSSs, and plants have evolved certain mechanisms to fight RSSs.
- Viruses may have acquired counter-defense mechanisms against antiviral silencing, but plants have counter-counter-defenses to combat them.
- Increasing evidence shows that RNA silencing plays a crucial role in plant–virus interactions.
- RNA silencing can be triggered by viral dsRNA generated either by replication intermediates or by secondary intramolecular RNA folding (hairpin) in host cells.
- The viral dsRNA is then incorporated into the RNA-induced silencing complex and guides Argonaute (AGO) proteins to the targeted RNA for degradation or translational arrest.
- RNA-dependent RNA polymerase (RDR) 6 is responsible for the secondary amplification of small RNAs (sRNAs).
- RNA silencing can also occur in a systemic manner, spreading from the initially infected cells to the rest of the plant through plasmodesmata and phloem.
- RNA silencing is effective against both RNA and DNA viruses.
- The co-evolutionary plant–virus interaction context shows that viruses may have acquired counter-defense mechanisms against antiviral silencing, but plants have evolved counter-counter-defense responses.
- Tomato spotted wilt virus (TSWV)-derived dsRNA application for virus resistance induction in tobacco is a promising prospect for spray-induced gene silencing.
- RNA silencing plays a crucial role in plant defense against viruses.
- RNA silencing is a powerful defense mechanism that can be used to develop transgenic virus resistance.
- RNA silencing can be triggered by exogenous applications of dsRNA or siRNA for disease protection.
- RNA silencing is an effective defense mechanism against viral RSSs.
- Plants have evolved certain mechanisms to fight viral RSSs, regarded as counter-counter-defense responses.
- RNA silencing can be used to develop virus resistance in a transgenic plant expressing a viral sequence.
- The coat protein (CP)-mediated transgenic papaya resistance against papaya ringspot virus through RNA silencing is a successful application of this technology.
Test your knowledge on dominant and recessive plant virus resistance genes, and the host factors critical for viral infection. Explore the relationship between eukaryotic translation initiation factors and plant defense mechanisms.
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