Suppression of Infectious TMV Genomes Expressed in Young Transgenic Tobacco Plants

• Published in: Molecular plant-microbe interactions Vol. 20; no. 12; pp. 1489 - 1494
• Main Authors: Siddiqui S.A, Sarmiento, C, Valkonen, S, Truve, E, Lehto, K
• Format: Journal Article
• Language: English
• Published: St Paul, MN APS Press 01-12-2007; The American Phytopathological Society
• Subjects: Biological and medical sciences; coat proteins; complementary DNA; disease course; DNA Methylation; Fundamental and applied biological sciences. Psychology; gene expression regulation; genes; Genome, Viral; host-pathogen relationships; Immunity, Innate; microbial genetics; molecular sequence data; Nicotiana - genetics; Nicotiana - growth & development; Nicotiana - virology; Nicotiana tabacum; nucleotide sequences; Phytopathology. Animal pests. Plant and forest protection; plant defense; plant development; Plant Diseases - virology; plant growth; plant stress; Plant viruses and viroids; Plants, Genetically Modified - metabolism; Plants, Genetically Modified - virology; promoter regions; RNA interference; RNA, Viral - metabolism; seed germination; signs and symptoms (plants); silencing suppressors; tobacco; Tobacco mosaic virus; Tobacco Mosaic Virus - genetics; transgenic plants; virus replication; Plant pathogen; Suppression; Stimulant plant; Tobamovirus; Nicotiana tabacum; Endogenous; Messenger RNA; Gene; Tobacco mosaic virus; Dicotyledones; silencing suppressors; Angiospermae; Transgenic plant; Solanaceae; Ribozyme; Germination; Protein; Stress; Virus; Resistance; Gene silencing; plant defense; Complementary DNA; Spermatophyta; Mutation; Genome; Methylation
• ISSN: 0894-0282; 1943-7706
• DOI: 10.1094/MPMI-20-12-1489

Full-length cDNAs of the wild-type (wt) Tobacco mosaic virus (TMV) and of the coat protein gene-deleted (ΔCP) derivative of wt-TMV, under control of the 35S promoter and downstream ribozyme sequence to produce accurate viral transcripts, were transformed to tobacco plants to analyze plant-virus interactions through different stages of plant development. Surprisingly, young wt-TMV transgenics accumulated only very low levels of viral RNA, remained free of symptoms, and were moderately resistant against exogenous inoculations. This early resistance caused significant stress to the plants, as indicated by reduced growth. Approximately 7 to 8 weeks after germination, the resistance was broken and plants developed typical wt-TMV symptoms, with high accumulation of the viral RNAs and proteins. The ΔCP-TMV plants likewise were initially resistant to the endogenous inoculum and were stunted, although to a lesser extent than the wt-TMV plants. The resistance was broken at the same time as in the wt-TMV plants, but the mutant replicated to much lower levels and produced much milder symptoms than the wt virus. TMV-specific small interfering RNAs as well as increased transgene methylation were detected in the plants only after the resistance break, indicating that the resistance in the young plants was not due to RNA silencing.