Endogenous Viral Elements in Plant Genomes

Endogenous Viral Elements in Plant Genomes

• Most endogenous pararetroviral elements (EPREs) in plant genomes are non-infective due to fragmentation by deletions, mutations, or epigenetic modifications.
• Rice tungro bacilliform virus (RTBV) DNA segments have been identified within several loci in rice genome databases, indicating integration into the host genome.
• Endogenous RTBV seems to have been generated by transcription from tandemly arranged integrants or by recombination from fragmented integrants in rice genomes.
• RTBV has been identified as the infectious agent of rice tungro diseases independent of its EPREs.
• Genomic sequences of Solanum lycopersicum and S. habrochaites reveal sequence similarity between their EPREs, named LycEPRVs, indicating potential derivation from one pararetrovirus.
• TA simple sequence repeats from endogenous florendoviruses have extensively colonized the genomes of two monocotyledonous and 19 dicotyledonous plant species.
• Endogenous non-retroviral elements (ENREs) in host plant genomes are derived from segmented and rearranged viral sequences of dsRNA, ssDNA, or ssRNA viruses.
• ENREs predominantly match RNA-dependent RNA polymerase (RdRP)-like, movement protein (MP)-like, and coat protein (CP)-like sequences of dsRNA viruses.
• Host plant genomes contain sequences from negative-ssRNA [ss(-)RNA] viruses, homologous to CP-like sequences of cytorhabdovirus and varicosavirus.
• Nucleotide sequences homologous to CP gene and 3′-UTR of a potyvirus or to a portion of CP and MP genes of cucumber mosaic virus have been identified in grape and Medicago truncatula genomic databases.
• Repetitive geminivirus-related DNA (GRD) sequences have been discovered in host genomes, resulting from promiscuous integration of multiple repeats of the geminivirus initiation (Rep) sequence.
• Few studies have focused on the benefits of virus latent infection and endogenous viral elements (EVEs) for host plants or the mutualistic symbioses between these and their host organisms.