title: Replication of Tomato Yellow Leaf Curl Virus in Its Whitefly Vector, Bemisia tabaci.
abstract: Tomato yellow leaf curl virus (TYLCV) is a begomovirus transmitted exclusively by the whitefly Bemisia tabaci in a persistent, circulative manner. Replication of TYLCV in its vector remains controversial, and thus far, the virus has been considered to be nonpropagative. Following 8 h of acquisition on TYLCV-infected tomato plants or purified virions and then transfer to non-TYLCV-host cotton plants, the amounts of virus inside whitefly adults significantly increased (>2-fold) during the first few days and then continuously decreased, as measured by the amounts of genes on both virus DNA strands. Reported alterations in insect immune and defense responses upon virus retention led us to hypothesize a role for the immune response in suppressing virus replication. After virus acquisition, stress conditions were imposed on whiteflies, and the levels of three viral gene sequences were measured over time. When whiteflies were exposed to TYLCV and treatment with two different pesticides, the virus levels continuously increased. Upon exposure to heat stress, the virus levels gradually decreased, without any initial accumulation. Switching of whiteflies between pesticide, heat stress, and control treatments caused fluctuating increases and decreases in virus levels. Fluorescence in situ hybridization analysis confirmed these results and showed virus signals inside midgut epithelial cell nuclei. Combining the pesticide and heat treatments with virus acquisition had significant effects on fecundity. Altogether, our results demonstrate for the first time that a single-stranded DNA plant virus can replicate in its hemipteran vector.
  
  
  OBJECTIVE
  Plant viruses in agricultural crops are of great concern worldwide. Many of them are transmitted from infected to healthy plants by insects. Persistently transmitted viruses often have a complex association with their vectors; however, most are believed not to replicate within these vectors. Such replication is important, as it contributes to the virus's spread and can impact vector biology. Tomato yellow leaf curl virus (TYLCV) is a devastating begomovirus that infects tomatoes. It is persistently transmitted by the whitefly Bemisia tabaci but is believed not to replicate in the insect. To demonstrate that TYLCV is, in fact, propagative (i.e., it replicates in its insect host), we hypothesized that insect defenses play a role in suppressing virus replication. We thus exposed whitefly to pesticide and heat stress conditions to manipulate its physiology, and we showed that under such conditions, the virus is able to replicate and significantly influence the insect's fecundity.
authors.affiliation: Institute of Plant Protection, Department of Entomology, Agricultural Research Organization, the Volcani Center, Bet Dagan, Israel.
authors.forename: Britto Cathrin
authors.initials: BC
authors.lastname: Pakkianathan
authors.affiliation: Institute of Plant Protection, Department of Entomology, Agricultural Research Organization, the Volcani Center, Bet Dagan, Israel.
authors.forename: Svetlana
authors.initials: S
authors.lastname: Kontsedalov
authors.affiliation: Institute of Plant Protection, Department of Entomology, Agricultural Research Organization, the Volcani Center, Bet Dagan, Israel.
authors.forename: Galina
authors.initials: G
authors.lastname: Lebedev
authors.affiliation: Institute of Plant Sciences and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
authors.forename: Assaf
authors.initials: A
authors.lastname: Mahadav
authors.affiliation: Al-Qasemi Research Center, Baqa Elgharbia, Israel.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Zeidan
authors.affiliation: Institute of Plant Sciences and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
authors.forename: Henryk
authors.initials: H
authors.lastname: Czosnek
authors.affiliation: Institute of Plant Protection, Department of Entomology, Agricultural Research Organization, the Volcani Center, Bet Dagan, Israel ghanim@agri.gov.il.
authors.forename: Murad
authors.initials: M
authors.lastname: Ghanim
mesh_terms: D000818:Animals; D053839:Begomovirus / Q000187:drug effects / Q000502:physiology*; D017931:DNA Primers / Q000235:genetics; D004279:DNA, Viral / Q000032:analysis; D005298:Fertility / Q000187:drug effects; D015967:Gene Expression Regulation, Viral / Q000276:immunology*; D006430:Hemiptera / Q000187:drug effects / Q000276:immunology / Q000821:virology*; D006358:Hot Temperature; D017404:In Situ Hybridization, Fluorescence; D007303:Insect Vectors / Q000187:drug effects / Q000276:immunology / Q000821:virology*; D010575:Pesticides / Q000633:toxicity; D014779:Virus Replication / Q000502:physiology*
chemical_list: D017931:DNA Primers; D004279:DNA, Viral; D010575:Pesticides