Abstract
Endornaviruses include viruses that infect fungi, oomycetes, and plants. The genome of plant endornaviruses consists of linear ssRNA ranging in size from approximately 13-18 kb and lacking capsid protein and cell-to-cell movement capability. Although, plant endornaviruses have not been shown to cause detectable changes in the plant phenotype, they have been associated with alterations of the host physiology. Except for the association of cytoplasmic vesicles with infections by Vicia faba endornavirus, effects on the plant cell ultrastructure caused by endornaviruses have not been reported. Bell pepper endornavirus (BPEV) has been identified in several pepper (Capsicum spp.) species. We conducted ultrastructural analyses of cells from two near-isogenic lines of the bell pepper (C. annuum) cv. Marengo, one infected with BPEV and the other BPEV-free, and found cellular alterations associated with BPEV-infections. Some cells of plants infected with BPEV exhibited alterations of organelles and other cell components. Affected cells were located mainly in the mesophyll and phloem tissues. Altered organelles included mitochondrion, chloroplast, and nucleus. The mitochondria from BPEV-infected plants exhibited low number of cristae and electron-lucent regions. Chloroplasts contained plastoglobules and small vesicles in the surrounding cytoplasm. Translucent regions in thylakoids were observed, as well as hypertrophy of the chloroplast structure. Many membranous vesicles were observed in the stroma along the envelope. The nuclei revealed a dilation of the nuclear envelope with vesicles and perinuclear areas. The organelle changes were accompanied by membranous structure rearrangements, such as paramural bodies and multivesicular bodies. These alterations were not observed in cells from plants of the BPEV-free line. Overall, the observed ultrastructural cell alterations associated with BPEV are similar to those caused by plant viruses and viroids and suggest some degree of parasitic interaction between BPEV and the plant host.
Highlights
Peppers (Capsicum species in the family Solanaceae) are native plants from the Americas and are cultivated worldwide as food crops (DeWitt and Bosland, 1996; Pickersgill, 1997)
The genomes of these viruses do not code for a capsid protein (CP), and it is not surprising that virions have not been reported in endornavirusinfected cells (Valverde et al, 1990; Zabalgogeazcoa and Gildow, 1992; Fukuhara, 1999)
The replicative form of the genomic RNA of Vicia faba endornavirus (VfEV)-infected V. faba has been found to be associated with cytoplasmic vesicles and viral dsRNA isolated from purified vescicles (Lefebvre et al, 1990)
Summary
Peppers (Capsicum species in the family Solanaceae) are native plants from the Americas and are cultivated worldwide as food crops (DeWitt and Bosland, 1996; Pickersgill, 1997). Based on host symptom expression, plant viruses can be divided into two categories: acute and persistent (Roossinck, 2010). Acute viruses are transmitted horizontally and, in some cases, vertically. Persistent viruses do not cause morphological symptoms; they lack MP and are transmitted only vertically via gametes (Roossinck, 2010; Fukuhara, 2019). Persistent plant viruses include members of the families Amalgaviridae, Chrysoviridae, Endornaviridae, Nardaviridae, Partitiviridae, and Totiviridae (Roossinck, 2010; Nibert et al, 2018; Fukuhara, 2019; Takahashi et al, 2019). Interactions of persistent viruses with the host, acute viruses, and other biotic and abiotic agents have not been investigated
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