Molecular Pathogens 2024, Vol.15, No.4, 189-199 http://microbescipublisher.com/index.php/mp 194 5.2 Host immune responses to viral infection 5.2.1 Activation of pattern recognition receptors (PRRs) Pattern recognition receptors (PRRs) are essential components of the plant immune system that detect pathogen-associated molecular patterns (PAMPs) and initiate immune responses. In rice, PRRs such as receptor-like kinases (RLKs) and receptor-like proteins (RLPs) recognize viral PAMPs and activate downstream signaling pathways, leading to the expression of antiviral genes. This process is crucial for the early detection and response to viral infections (Saijo et al., 2018; Carty et al., 2020). 5.2.2 RNA silencing mechanism in rice RNA silencing is a primary antiviral defense mechanism in rice. It involves the production of vsiRNAs that guide the RNA-induced silencing complex (RISC) to degrade viral RNA. Viruses, in turn, have evolved viral suppressors of RNA silencing (VSRs) to counteract this defense. For instance, members of the Closteroviridae family encode VSRs that inhibit RNA silencing, allowing the virus to replicate and spread. The interplay between RNA silencing and VSRs represents a dynamic arms race between the host and the virus (Hussain et al., 2021). 5.2.3 Hormonal regulation in virus defense Phytohormones such as jasmonates (JAs) play a significant role in regulating antiviral defenses in rice. JA signaling can enhance RNA silencing by upregulating key components such as Argonaute 18 (AGO18). This upregulation is mediated by the JA-responsive transcription factor JAMYB, which binds to the AGO18 promoter. The interaction between JA signaling and RNA silencing pathways exemplifies the complex regulatory networks that rice plants employ to defend against viral infections (Calil and Fontes, 2016; Yang et al., 2020). 5.3 Symbiotic or antagonistic roles of mycoviruses in rice cultivation Mycoviruses, which infect fungi, can have both symbiotic and antagonistic effects on rice cultivation. Symbiotic mycoviruses can enhance the fitness of their fungal hosts, potentially benefiting rice plants by improving nutrient uptake or stress tolerance. Conversely, antagonistic mycoviruses can weaken pathogenic fungi, reducing their virulence and thereby protecting rice plants from fungal diseases. Understanding the dual roles of mycoviruses in rice cultivation could lead to novel strategies for managing rice diseases and improving crop resilience. 6 Current and Emerging Control Strategies 6.1 Traditional control methods: cultural practices and chemical treatments Traditional control methods for managing viral and mycoviral threats in rice cultivation include cultural practices and chemical treatments. Cultural practices such as crop rotation, proper field sanitation, and the use of resistant varieties have been employed to reduce the incidence of diseases. Chemical treatments, including the application of fungicides and insecticides, have also been widely used to control the spread of pathogens. However, these methods have limitations, including the development of resistance in pathogens and environmental concerns associated with chemical use. 6.2 Breeding for virus-resistant rice varieties Breeding for virus-resistant rice varieties is a sustainable and effective approach to managing viral threats. Traditional breeding methods, along with molecular marker-based breeding approaches, have been instrumental in developing resistant cultivars. The identification and utilization of resistance (R) genes and quantitative trait loci (QTL) have significantly contributed to the development of broad-spectrum disease-resistant rice varieties (Nizolli et al., 2021). Marker-assisted selection (MAS) and marker-assisted backcross breeding (MABB) have accelerated the breeding process, enabling the development of durable resistance against various pathogens. 6.3 Biotechnological approaches: gene editing and RNA interference Biotechnological approaches, including gene editing and RNA interference (RNAi), have revolutionized the development of disease-resistant rice varieties. The CRISPR/Cas9 system has emerged as a powerful tool for precise genome editing, allowing for the modification of specific genes associated with disease resistance (Figure 3) (Cao et al., 2020; Mishra et al., 2021). RNAi technology has been used to silence viral genes, providing an
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