Defenses against Virus and Vector: A Phloem-Biological Perspective on RTM- and SLI1-Mediated Resistance to Potyviruses and Aphids

Abstract

Combining plant resistance against virus and vector presents an attractive approach to reduce virus transmission and virus proliferation in crops. Restricted Tobacco-etch virus Movement (RTM) genes confer resistance to potyviruses by limiting their long-distance transport. Recently, a close homologue of one of the RTM genes, SLI1, has been discovered but this gene instead confers resistance to Myzus persicae aphids, a vector of potyviruses. The functional connection between resistance to potyviruses and aphids, raises the question whether plants have a basic defense system in the phloem against biotic intruders. This paper provides an overview on restricted potyvirus phloem transport and restricted aphid phloem feeding and their possible interplay, followed by a discussion on various ways in which viruses and aphids gain access to the phloem sap. From a phloem-biological perspective, hypotheses are proposed on the underlying mechanisms of RTM- and SLI1-mediated resistance, and their possible efficacy to defend against systemic viruses and phloem-feeding vectors.

Comparative plant transcriptome profiling of Arabidopsis and Camelina infested with Myzus persicae aphids acquiring circulative and non-circulative viruses reveals virus- and plant-specific alterations relevant to aphid feeding behavior and transmission

“…The reduced pathway phase and the increased phloem ingestion might also facilitate CaMV acquisition from phloem tissues. These alterations are expected to be detrimental for non-circulative viruses (such as the non-persistent potyviruses) that are acquired during intracellular penetrations occurring in the pathway phase, but lost if the aphid stylets reach the phloem sap (Kloth and Kormelink, 2020). However, this does not apply to CaMV, acquired efficiently from phloem sap as well as mesophyll and epidermis cells (Palacios et al, 2002).…”

Cauliflower mosaic virus protein P6‐TAV plays a major role in alteration of aphid vector feeding behaviour but not performance on infected Arabidopsis

“…Different letters indicate significant differences between plants as tested by GLM followed by pairwise comparisons using "emmeans" (p < .05; method: Tukey, n = 25-31) mosaic virus (single-stranded RNA viruses of families Potyviridae and Bromoviridae, respectively) are acquired during short intracellular stylet punctures in plant epidermis and mesophyll (Martin et al, 1997). They are lost from the stylets when aphids stay on plants for longer times and when the stylets reach the sieve tubes that do not contain transmission-competent virus forms (Kloth & Kormelink, 2020;Wang & Ghabrial, 2002). The case is different for CaMV that is acquired efficiently from both cells and phloem sap and after both short and long acquisition periods (Bouchery et al, 1990;Markham et al, 1987;Palacios et al, 2002).…”

Multiomic analisys reveals that viroid infection induces a temporal reprograming of plant-defence mechanisms at multiple regulatory levels

“…RTM1 and RTM2 genes encode a jacalin-repeat protein and a transmembrane-containing small heat-shock-like (hsp20-like) protein, respectively, and are involved in a functional mechanism responsible of the specific restriction of the long-distance movement of Tobacco etch potyvirus (TEV) in A. thaliana (93). Although the basis of this phenomenon is unclear, it has been proposed that the restriction could be the result of physical blockage of virus entry into, passage through, or exit from the phloem (94).…”