Persistent, circulative transmission of begomoviruses by whitefly vectors Ran Rosen 1 , Surapathrudu Kanakala 1 , Adi Kliot 1 , Britto Cathrin Pakkianathan 1 , Basheer Abu Farich 1,2 , Nadine Santana-Magal 1 , Meytar Elimelech 1 , Svetlana Kontsedalov 1 , Galina Lebedev 1 , Michelle Cilia 3,4,5 and Murad Ghanim 1 Begomoviruses comprise an emerging and economically important group of plant viruses exclusively transmitted by the sweetpotato whitefly Bemisia tabaci in many regions of the world. The past twenty years have witnessed significant progress in studying the molecular interactions between members of this virus group and B. tabaci. Mechanisms and proteins encoded by the insect vector and its bacterial symbionts, which have been shown to be important for virus transmission, have been identified and thoroughly studied. Despite the economic importance of this group of viruses and their impact on the global agriculture, progress in investigating the virus–vector interactions is moving slowly when compared with similar virus–vector systems in plants and animals. Major advances in this field and future perspectives will be discussed in this review. Addresses 1 Department of Entomology, Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel 2 Al-Qasemi Research Center, Al-Qasemi Academic College, P. O. Box 124, Baqa El-Gharbia 30100, Israel 3 Boyce Thompson Institute for Plant Research, Ithaca, NY 14853, United States 4 Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, NY 14853, United States 5 Agricultural Research Service, Biological Integrated Pest Management Research Unit, Ithaca, NY 14853, United States Corresponding author: Ghanim, Murad (ghanim@agri.gov.il) Current Opinion in Virology 2015, 15:1–8 This review comes from a themed issue on Virus–vector interactions Edited by Anne E Simon and Scott C Weaver http://dx.doi.org/10.1016/j.coviro.2015.06.008 1879-6257/# 2015 Elsevier B.V. All rights reserved. Introduction Begomoviruses are the largest group of viruses within the family Geminiviridae [1]. Viruses in this group are char- acterized by geminate particles comprised of two joined, incomplete icosahedra encapsidating circular single stranded DNA genome molecules of about 2700 bp [2,3]. Generally, begomoviruses possess two genomic components, DNA-A and DNA-B (bipartite) (reviewed in [4  ,5,6  ]); however, some family members, such as Tomato yellow leaf curl virus (TYLCV), are monopartite with a single DNA-A-like genome component [2]. The DNA-A of bipartite and the single component of mono- partite begomoviruses contain five to six Open Reading Frames (ORFs), one or two (AV1 and AV2) in the viral sense strand (V-sense) and four (AC1–AC4) in the com- plementary sense strand (C-sense). AV1 codes for the viral capsid protein (CP) and V2 (the gene abbreviation’s initial letter, A or B refer to the DNA-A or DNA-B genome which encode the gene, thus in monopartite begomovirus this letter is absent) from TYLCV was shown to function as a suppressor of gene silencing in infected tomato plants [7]. Genes on the C strand and the B component code for proteins involved replication, pathogenicity and move- ment. In addition, there is a noncoding region (IR) which contains the origin of replication and also harbors promoter and regulatory elements for viral gene expression. Mono- partite begomoviruses are often associated with one or more smaller DNA (1.4 kb), subviral components known as satellite DNAs (reviewed in [4  ,5]). Begomoviruses are transmitted exclusively by the sweet- potato whitefly Bemisia tabaci in a persistent-circulative manner, although one report suggested that the castor bean whitefly Trialeurodes ricini can also transmit TYLCV [8]. B. tabaci is a complex of cryptic species that comprises at least 37 species formerly termed biotypes which can be differentiated mainly by DNA markers [9  ,10–12]. The species in this complex differ in host range, resistance to insecticide, virus transmission, and their ability to induce plant disorders. The most predominant and damaging worldwide are the Middle East Asia Minor 1 (MEAM1) (formerly termed B biotype) and the Mediterranean (MED) (formerly termed Q biotype) species [13,14]. MEAM1 and MED are distributed worldwide and have invaded many countries mainly through international trade and changes in agricultural practices that sometimes lead to displacement of one species by another. Such examples include MED invasion in the United States Available online at www.sciencedirect.com ScienceDirect www.sciencedirect.com Current Opinion in Virology 2015, 15:1–8