Lower temperature influences Cauliflower mosaic virus systemic infection

Authors: ALERS-VELAZQUEZ, R - University Of Toledo; KHANDEKAR, SUSHANT - University Of Toledo; MULLER, CLARE - University Of Toledo; Boldt, Jennifer; LEISNER, SCOTT - University Of Toledo

Submitted to: Journal of General Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/18/2021
Publication Date: 3/28/2021
Citation: Alers-Velazquez, R., Khandekar, S., Muller, C., Boldt, J.K., Leisner, S. 2021. Lower temperature influences Cauliflower mosaic virus systemic infection. Journal of General Plant Pathology. 87:242-248. https://doi.org/10.1007/s10327-021-01003-y.
DOI: https://doi.org/10.1007/s10327-021-01003-y

Interpretive Summary: Plant viruses limit plant growth and crop yield. Environmental conditions can influence the severity of a viral infection, but the underlying mechanisms are not well known. Understanding how temperature impacts a virus’s ability to reproduce and spread within a plant will allow researchers to develop crop production recommendations which favor crop growth and lessen the severity of an infection. In two host plant species, a slightly lower air temperature (18 vs 22 °C) delayed Cauliflower mosaic virus (CaMV) systemic infection. This was not due to reduced viral nucleic acid levels (DNA and RNA), which were actually higher at the lower temperature. However, viral coat protein levels were reduced at the lower temperature. This suggests that although viral RNA levels were increased, CaMV may be somewhat defective in either protein synthesis or virion production at the lower temperature. Within the host plant cells, inclusion bodies (structures where virus proteins, DNA, and viral particles are assembled) and the actin cytoskeleton (filaments which inclusion bodies utilize for formation and movement) were altered at the lower temperature. Our results suggest that lower temperatures appear to alter the host plant cell’s actin cytoskeleton, impairing inclusion body formation, and ultimately affecting overall virus coat protein and virion production in plants. This discovery furthers researchers’ understanding of virus reproduction and spread in plants. Additionally, it may lead to new temperature-based strategies for controlling plant viral infections, especially CaMV, which capitalize on growing crops at temperatures which hinder viral spread within the plant after infection.

Technical Abstract: Plant virus disease outbreaks are frequently associated with lower growth conditions, probably because low temperatures can inactivate host defenses. However, Cauliflower mosaic virus (CaMV), a member of the plant pararetrovirus family Caulimoviridae, shows a more complex relationship. Lower temperatures delayed CaMV systemic symptoms in two different plant hosts, turnips and O.violaceus In contrast to the symptom data, the lower temperature increased CaMV RNA and DNA levels in systemically-infected leaves. However, the lower temperature appeared to reduce virus coat protein levels. Virus protein synthesis, genome replication, and virion assembly occur in virus-produced cytoplasmic structures called inclusion bodies (IBs). IB size distribution was altered at the lower temperature, favoring the formation of larger bodies. IBs move along actin filaments. The lower temperature altered the organization of the actin cytoskeleton, possibly facilitating fusion of smaller IBs into larger ones. The lower temperature employed in this study did not cause stress in the plant host biochemistry based on measurement of photosynthetic parameters. Taken together, these data suggest that lower temperatures alter the actin cytoskeleton, affecting IB formation, thereby causing an impairment of viral coat protein levels and possibly a delay in systemic infection.