Legume-infecting Begomoviruses: Diversity and Host Interaction

摘要: The legume yellow mosaic viruses (LYMVs) are members of the proposed sub-genus “Legumovirus” within genus Begomovirus family Geminiviridae; single-stranded DNA transmitted by whitefly Bemisia tabaci.The legumoviruses evolutionarily distinct from all other begomoviruses and interest for this reason as well losses they cause to leguminous crops across southern AsiaThere four LYMVs (Mungbean virus [MYMV], Mungbean India [MYMIV], Dolichos [DoYMV] Horsegram [HgYMV]) that have been shown be responsible disease (YMD) legumes Asia. An analysis genetic diversity Pakistan was conducted.Samples were collected 11 districts 48 full-length begomovirus components (25 DNA-A, 21 DNA-B) cloned sequenced in their entirety. Analysis these sequences showed MYMIV is most prevalent causal agent YMD shows phylogeographic segregation; no species crops. MYMV, which major pathogen western India, also identified but only a weed, Rhynchosia capitata. In addition novel begomovirus, with less than 70% nucleotide sequence identity begomoviruses, isolated another minima.This newly belong LYMV cluster tentatively named (RhYMV). As components, two not commonly (Pedilanthus leaf curl [PedLCV] Papaya [PaLCuV]) betasatellite (Tobacco [TbLCB]) some infected showing typical symptoms. Constructs Agrobacterium-mediated inoculation representative isolates produced.The MYMV infect blackgram, inducing very mild symptoms. RhYMV infectious lines soybean any tested.The limited host range possibly explains absence crops.In contrast, MYMIV, (MYMIV-Sb) mungbean (MYMIV-Mg) differing infectivities legumes.The isolate high levels infectivity low whereas highly blackgram poorly mungbean. This suggests adapted hosts.None examined non-legume Nicotiana benthamiana, used an experimentally dicot-infecting has investigated. first time lack N. benthamiana reported. Similarly tabacum. The identification grave concern due possibility it increasing severity. TbLCB capacity maintained RhYMV, trans-replicated LYMV, extend benthamiana. Although DNA-B three had role play such infections (co-inoculation or expression encoded MP under control 35S promoter increased DNA-A 60% 100%), DNA-B, complemented usual functions DNA-Bs viruses.This ability complement function gene product betasatellites, βC1. Expression βC1 PVX transiently allowed move systemically However, when expressed using promoter, tissues symptoms ensued, suggesting assists infection acts at site does spread. The results obtained indicate N.benthamiana adaptation DNA-B-encoded products host.Thus TbLCB, one several monopartite (including PedLCV), able efficiently spread systemically.In addition, plant host-defense mediated RDR6 small limiting silencing VIGS did allow induce symptomatic infection. At transformation many legumes, particularly grain problematic, precluding use legume-transformation study derived resistance LYMVs. Using system, based upon complementation movement potentially useful model studies.Using transient antisense Rep construct, (in presence TbLCB) reduced 90%.This indicates RNAi may tool reducing Asia assisted system provides means selecting efficient constructs prior protocols local becoming available.