Molecular Entomology 2024, Vol.15, No.5, 170-178 http://emtoscipublisher.com/index.php/me 171 This study integrates current knowledge on the mechanisms by which aphids transmit viruses and their interactions with host plants, examining the latest advancements in this field, including the role of aphid biology and morphology in virus transmission, the impact of viral infection on aphid feeding behavior, and the molecular interactions among plant viruses, aphids, and host plants, to provide a comprehensive understanding of factors influencing aphid-mediated virus transmission, with the goal of identifying potential targets for developing sustainable management strategies to mitigate the impact of aphid-transmitted viruses on global agriculture. 2 Mechanisms of Virus Transmission by Aphids 2.1 Non-persistent transmission Non-persistent transmission involves viruses that are acquired and transmitted by aphids within a short period, typically during brief probing of the plant epidermis. These viruses do not circulate within the aphid's body but are retained in the stylets. For instance, the Papaya Ringspot Virus (PRSV) is transmitted in a non-persistent manner by the melon aphid (Aphis gossypii). PRSV-infected plants enhance the fitness and feeding behavior of A. gossypii, likely through nutrient enrichment, which in turn facilitates virus transmission (Gadhave et al., 2019). Potyviruses, the largest group of plant-infecting RNA viruses, are also predominantly transmitted non-persistently by aphids, influencing aphid behavior and host plant biochemistry to enhance transmission efficiency (Gadhave et al., 2020). 2.2 Semi-persistent transmission In semi-persistent transmission, viruses are retained in the foregut or salivary glands of the aphid but do not circulate within the insect's body. These viruses can be retained for a longer period compared to non-persistent viruses. The transmission process involves specific interactions between the virus capsid and retention sites in the vector. For example, Non-Circulative, Semi-Persistent (NCSP) viruses have evolved mechanisms to bind to specific sites in the aphid's foregut, facilitating prolonged retention and transmission. This mode of transmission is influenced by the vector's feeding behavior and the plant's response to virus infection, which can alter vector attraction and feeding patterns (Zhou et al., 2018). 2.3 Persistent transmission Persistent transmission involves viruses that circulate within the aphid's body, moving from the gut to the hemolymph and eventually to the salivary glands. These viruses can be retained for the lifetime of the aphid. For instance, the Turnip Yellows Virus (TuYV) is transmitted persistently by aphids in a circulative, non-propagative manner. TuYV infection alters the host plant's metabolic composition, reducing defense responses and enhancing the plant's suitability as a feeding site, which promotes higher transmission efficiency (Chesnais et al., 2022; Krieger et al., 2023). Persistent viruses manipulate plant traits to create a more favorable environment for aphid feeding and virus transmission over extended periods (Shi et al., 2021). 2.4 Circulative and non-circulative pathways Viruses transmitted by aphids can follow either circulative or non-circulative pathways. In the circulative pathway, viruses enter the aphid's gut, circulate through the hemolymph, and reach the salivary glands, as seen with TuYV (Krieger et al., 2023). In contrast, non-circulative viruses, such as potyviruses, are retained in the stylets or foregut and do not enter the hemolymph. The mode of transmission (circulative or non-circulative) significantly influences the virus-vector-plant interactions, with circulative viruses often inducing more profound changes in plant physiology to enhance vector attraction and feeding (Chesnais et al., 2022). 2.5 Factors influencing transmission efficiency Several factors influence the efficiency of virus transmission by aphids, including the virus's ability to manipulate host plant traits, the vector's feeding behavior, and the presence of endosymbionts. For example, the presence of the endosymbiont Buchnera aphidicola in aphids can modulate the volatile profile of host plants, affecting aphid feeding preferences and virus transmission dynamics (Shi et al., 2021). Additionally, virus-induced changes in plant defense responses and nutrient profiles can either enhance or deter aphid feeding, thereby influencing transmission efficiency (Gadhave et al., 2019; Shi et al., 2021; Krieger et al., 2023). Understanding these complex interactions is crucial for developing effective strategies to manage aphid-transmitted plant viruses.
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