Geminiviruses

Geminiviruses - Single-Stranded DNA Viruses of Plants...

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Single-Stranded DNA Viruses of Plants Jeewan Jyot Mic-162
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There are currently 18 families ( dae ) of plant viruses; plus 81 genera ( virus ; not including viroids and other subviral agents). 75% of plant viruses are ssRNA viruses Few have ssDNA or dsDNA genomes Most of the animal and bacterial viruses have DNA genomes
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Three families of Plant infecting DNA viruses Caulimoviridae : ds DNA viruses, monopartite genomes, have reverse transcribing phase in their life cycle. Ex. Cauliflower mosaic virus , Commelina yellow mottle virus , Rice tungro bacilliform virus Geminiviridae : circular ssDNA viruses, mono or bipartite genome, twinned icosahedral particles, transmitted by insects. Ex. Beet curly top virus , Bean golden mosaic virus Nanoviridae : circular ssDNA viruses, multipartite genome varies from 6-8 segments, vector transmitted. Ex. Faba bean necrotic yellows virus , Subterranean clover stunt virus , Banana bunchy top virus
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Geminiviridae – Historical perspective Among the earliest described virus diseases – Yellowing of Eupatorium chinense described in ancient Japanese poem (752AD) – Aesthetically pleasant symptoms Prized for leaf variegations Plants maintained by vegetative propagation Sold by commercial nurseries Abutilon mosaic
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Economically important plant diseases - Geminiviridae Maize Streak virus African Cassava Mosaic virus Bean Golden Mosaic virus Beet Curly top virus Tomato yellow leaf curl virus Squash leaf curl virus Cotton leaf curl virus Cotton leaf crumple virus
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Geminiviridae Not well characterized until late ’70’s - Very small unstable virions - Phloem restricted - low titer - Difficult to purify - Difficult to transmit New methods helped in Geminiviridae study Density Gradient Centrifugation, Electron Microscope Emerged due to vector distribution and global movement of susceptible plants
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Symptoms caused by Geminiviruses in plants Leads to stunted and distorted growth Foliar abnormalities Yellow/green mosaics Interveinal chlorosis Leaf curling & crumpling Small leaves Abortion of flowers Reduced fruit size and fruit abnormalities Reduced yields
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Structure of Geminiviruses Structure of geminivirus particles (T=1) – consist of two twinned quasi-icosahedral.
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This note was uploaded on 02/16/2011 for the course MIC 162 taught by Professor Manning during the Spring '09 term at UC Davis.

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Geminiviruses - Single-Stranded DNA Viruses of Plants...

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