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1. Cassava brown streak virus evolves with a nucleotide-substitution rate that is typical for the family Potyviridae

   https://doi.org/10.1016/j.virusres.2024.199397  

   Mbewe, Willard; Mukasa, Settumba; Ochwo-Ssemakula, Mildred; Sseruwagi, Peter; Tairo, Fred; Ndunguru, Joseph; Duffy, Siobain (August 2024, Virus Research)

   The ipomoviruses (family Potyviridae) that cause cassava brown streak disease (cassava brown streak virus [CBSV] and Uganda cassava brown streak virus [UCBSV]) are damaging plant pathogens that affect the sustainability of cassava production in East and Central Africa. However, little is known about the rate at which the viruses evolve and when they emerged in Africa – which inform how easily these viruses can host shift and resist RNAi approaches for control. We present here the rates of evolution determined from the coat protein gene (CP) of CBSV (Temporal signal in a UCBSV dataset was not sufficient for comparable analysis). Our BEAST analysis estimated the CBSV CP evolves at a mean rate of 1.43 × 10^3 nucleotide substitutions per site per year, with the most recent common ancestor of sampled CBSV isolates existing in 1944 (95% HPD, between years 1922 – 1963). We compared the published measured and estimated rates of evolution of CPs from ten families of plant viruses and showed that CBSV is an average-evolving potyvirid, but that members of Potyviridae evolve more quickly than members of Virgaviridae and the single representatives of Betaflexiviridae, Bunyaviridae, Caulimoviridae and Closteroviridae. 

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2. Effector-mediated plant–virus–vector interactions

   https://doi.org/10.1093/plcell/koac058  

   Ray, Swayamjit; Casteel, Clare L (February 2022, The Plant Cell)

   Abstract Hemipterans (such as aphids, whiteflies, and leafhoppers) are some of the most devastating insect pests due to the numerous plant pathogens they transmit as vectors, which are primarily viral. Over the past decade, tremendous progress has been made in broadening our understanding of plant–virus–vector interactions, yet on the molecular level, viruses and vectors have typically been studied in isolation of each other until recently. From that work, it is clear that both hemipteran vectors and viruses use effectors to manipulate host physiology and successfully colonize a plant and that co-evolutionary dynamics have resulted in effective host immune responses, as well as diverse mechanisms of counterattack by both challengers. In this review, we focus on advances in effector-mediated plant–virus–vector interactions and the underlying mechanisms. We propose that molecular synergisms in vector–virus interactions occur in cases where both the virus and vector benefit from the interaction (mutualism). To support this view, we show that mutualisms are common in virus–vector interactions and that virus and vector effectors target conserved mechanisms of plant immunity, including plant transcription factors, and plant protein degradation pathways. Finally, we outline ways to identify true effector synergisms in the future and propose future research directions concerning the roles effectors play in plant–virus–vector interactions. 

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3. Why do viruses make aphids winged?

   https://doi.org/10.1111/imb.12860  

   Rozo‐Lopez, Paula; Parker, Benjamin J. (May 2023, Insect Molecular Biology)

   Abstract Aphids are hosts to diverse viruses and are important vectors of plant pathogens. The spread of viruses is heavily influenced by aphid movement and behaviour. Consequently, wing plasticity (where individuals can be winged or wingless depending on environmental conditions) is an important factor in the spread of aphid‐associated viruses. We review several fascinating systems where aphid‐vectored plant viruses interact with aphid wing plasticity, both indirectly by manipulating plant physiology and directly through molecular interactions with plasticity pathways. We also cover recent examples where aphid‐specific viruses and endogenous viral elements within aphid genomes influence wing formation. We discuss why unrelated viruses with different transmission modes have convergently evolved to manipulate wing formation in aphids and whether this is advantageous for both host and virus. We argue that interactions with viruses are likely shaping the evolution of wing plasticity within and across aphid species, and we discuss the potential importance of these findings for aphid biocontrol. 

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4. Oligogalactolipid production during cold challenge is conserved in early diverging lineages

   https://doi.org/10.1093/jxb/erad241  

   Barnes, Allison C.; Myers, Jennifer L.; Surber, Samantha M.; Liang, Zhikai; Mower, Jeffrey P.; Schnable, James C.; Roston, Rebecca L.; Nakamura, ed., Yuki (June 2023, Journal of Experimental Botany)

   Abstract Severe cold, defined as a damaging cold beyond acclimation temperatures, has unique responses, but the signaling and evolution of these responses are not well understood. Production of oligogalactolipids, which is triggered by cytosolic acidification in Arabidopsis (Arabidopsis thaliana), contributes to survival in severe cold. Here, we investigated oligogalactolipid production in species from bryophytes to angiosperms. Production of oligogalactolipids differed within each clade, suggesting multiple evolutionary origins of severe cold tolerance. We also observed greater oligogalactolipid production in control samples than in temperature-challenged samples of some species. Further examination of representative species revealed a tight association between temperature, damage, and oligogalactolipid production that scaled with the cold tolerance of each species. Based on oligogalactolipid production and transcript changes, multiple angiosperm species share a signal of oligogalactolipid production initially described in Arabidopsis, namely cytosolic acidification. Together, these data suggest that oligogalactolipid production is a severe cold response that originated from an ancestral damage response that remains in many land plant lineages and that cytosolic acidification may be a common signaling mechanism for its activation. 

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5. Intrinsic factors driving mosquito vector competence and viral evolution: a review

   https://doi.org/10.3389/fcimb.2023.1330600  

   Lewis, Juliette; Gallichotte, Emily N; Randall, Jenna; Glass, Arielle; Foy, Brian D; Ebel, Gregory D; Kading, Rebekah C (December 2023, Frontiers in Cellular and Infection Microbiology)

   Mosquitoes are responsible for the transmission of numerous viruses of global health significance. The term “vector competence” describes the intrinsic ability of an arthropod vector to transmit an infectious agent. Prior to transmission, the mosquito itself presents a complex and hostile environment through which a virus must transit to ensure propagation and transmission to the next host. Viruses imbibed in an infectious blood meal must pass in and out of the mosquito midgut, traffic through the body cavity or hemocoel, invade the salivary glands, and be expelled with the saliva when the vector takes a subsequent blood meal. Viruses encounter physical, cellular, microbial, and immunological barriers, which are influenced by the genetic background of the mosquito vector as well as environmental conditions. Collectively, these factors place significant selective pressure on the virus that impact its evolution and transmission. Here, we provide an overview of the current state of the field in understanding the mosquito-specific factors that underpin vector competence and how each of these mechanisms may influence virus evolution. 

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