Ultrastructural Analysis of Cells From Bell Pepper (Capsicum annuum) Infected With Bell Pepper Endornavirus

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.

Transcriptome analysis of two near-isogenic lines of bell pepper (Capsicum annuum) infected with bell pepper endornavirus and pepper mild mottle virus

“…These genes have been reported to be involved in the plant defense response. This is not surprising as it has been reported that BPEV can cause cellular ultrastructural changes in bell pepper ( Otulak-Koziel et al, 2020 ). Transcriptomic analysis of two lines (not NILs) of common bean, one infected with Phaseolus vulgaris endornavirus and the other endornavirus-free, revealed several upregulated genes involved in response to pathogen infection and environmental stresses ( Khankhum et al, 2016 ).…”

Genome Characterization and Phylogenetic Analysis of a Novel Endornavirus That Infects Fungal Pathogen Sclerotinia sclerotiorum

“…Further, Yang et al found that Sclerotinia minor endornavirus 1 (SmEV1) has horizontal and vertical transmission characteristics, and the mycelium fragments of strain LC22 can attenuate the virulence of S. minor [ 37 ]. Recent studies have found that plants infected by Bell pepper endornavirus (BPEV) have alterations of organelles and other cell components, which are believed to be caused by parasitic effects between the endornavirus and host [ 53 ]. Additionally, the coinfection of Phytophthora endornavirus 2 (PEV2) and Phytophthora endornavirus 3 (PEV3) also affects the sensitivity of oomycetes to fungicides [ 54 ].…”

Successful full-length genomic cloning and characterization of site-specific nick structures of Phytophthora endornaviruses 2 and 3 in yeast, Saccharomyces cerevisiae

“…These genomes contain one open reading frame (ORF), which encodes a single polyprotein consisting of 3,217–5,825 amino acid (aa) residues with several conserved domains, such as RNA-dependent RNA polymerase (RdRP), helicase (Hel), and UDP-glucosyl transferase (UGT) ( Valverde et al, 2019 ). Although endornaviruses have not been reported to possess capsid proteins, they have been suggested to be associated with vesicular membranes in the cytoplasm ( Lefebvre et al, 1990 ; Moriyama et al, 1996 ; Horiuchi et al, 2003 ; Otulak-Kozieł et al, 2020 ).…”