Abstract
As obligate intracellular phytopathogens, plant viruses must take advantage of hosts plasmodesmata and phloem vasculature for their local and long-distance transports to establish systemic infection in plants. In contrast to well-studied virus local transports, molecular mechanisms and related host genes governing virus systemic trafficking are far from being understood. Here, we performed a forward genetic screening to identify Arabidopsis thaliana mutants with enhanced susceptibility to a 2b-deleted mutant of cucumber mosaic virus (CMV-2aT∆2b). We found that an uncharacterized Piezo protein (AtPiezo), an ortholog of animal Piezo proteins with mechanosensitive (MS) cation channel activities, was required for inhibiting systemic infection of CMV-2aT∆2b and turnip mosaic virus tagged a green fluorescent protein (GFP) (TuMV-GFP). AtPiezo is induced by virus infection, especially in the petioles of rosette leaves. Thus, we for the first time demonstrate the biological function of Piezo proteins in plants, which might represent a common antiviral strategy because many monocot and dicot plant species have a single Piezo ortholog.
Highlights
Plant viruses are obligate parasites being largely dependent on their host for translation, replication, encapsidation, movement, and long-distance infection
At 7 dpi, green fluorescent protein (GFP) fluorescence in the mca[1], mca[2] single mutant plants, as well as mca[1] mca[2] double mutant plants was comparable to wild-type Col-0 plants, while esc[1,2] plants exhibited enhanced susceptibility to infection of Turnip mosaic virus (TuMV)-GFP (Supplementary Fig. S6). These results indicate that MCA1 and MCA2, unlike an uncharacterized Piezo protein (AtPiezo) protein, have no observable effects on systemic infections of TuMV-GFP
In contrast with MSL and MCA families, studies of which have gained breakthroughs in recent years[29,30,34,35], plant Piezo proteins and their biological functions are largely unknown except their similarity with the well-studied animal Piezo orthologs[28,36]
Summary
Plant viruses are obligate parasites being largely dependent on their host for translation, replication, encapsidation, movement, and long-distance infection. During long-distance transport, there are three main steps including viral entry into phloem tissues, movement within sieve elements, and exit into cells of the sink tissues (review in references)[1,2]. Cucumber mosaic virus (CMV) has a tripartite genome consisting of RNA1, RNA2 and RNA3, which encoded 1a protein possessing the helicase and methylase domain, an RNA-dependent RNA polymerase, and the viral movement protein (MP), respectively. CMV-2aTΔ2b, a CMV mutant with a 295-nt deletion in its 2b coding region and the overlapping C-terminus of CMV 2a protein, induces secondary siRNA amplification mediated by host RNA-dependent RNA Polymerase 1 (RDR1) and RDR612,13. Methylene blue-stained rRNA were used as loading controls for total RNAs
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