RESEARCH Open AccessComparison of phenotypes produced in responseto transient expression of genes encoded by fourdistinct begomoviruses in Nicotiana benthamianaand their correlation with the levels ofdevelopmental miRNAsImran Amin 1,2 , Basavaprabhu L Patil 2 , Rob W Briddon 1 , Shahid Mansoor 1* and Claude M Fauquet 2AbstractBackground: Whitefly-transmitted geminiviruses (begomoviruses) are a major limiting factor for the production ofnumerous dicotyledonous crops throughout the world. Begomoviruses differ in the number of components thatmake up their genomes and association with satellites, and yet they cause strikingly similar phenotypes, such as leafcurling, chlorosis and stunted plant growth. MicroRNAs (miRNAs) are small endogenous RNAs that regulate plantgrowth and development. The study described here was aimed at investigating the effects of each virus encodedgene on the levels of developmental miRNAs to identify common trends between distinct begomoviruses.Results: All genes encoded by four distinct begomoviruses (African cassava mosaic virus [ACMV], Cabbage leaf curlvirus [CbLCuV], Tomato yellow leaf curl virus [TYLCV] and Cotton leaf curl virus/Cotton leaf curl betasatellite [CLCuV/CLCuMB]) were expressed from a Potato virus X (PVX) vector in Nicotiana benthamiana. Changes in the levels of tenmiRNAs in response to the virus genes were determined by northern blotting using specific miRNA probes. For themonopartite begomoviruses (TYLCV and CLCuMV) the V2 gene product was identified as the major symptomdeterminant while for bipartite begomoviruses (ACMV and CbLCuV) more than one gene appears to contribute tosymptoms and this is reflected in changes in miRNA levels. The phenotype induced by expression of the bC1 geneof the betasatellite CLCuMB was the most distinct and consisted of leaf curling, vein swelling, thick green veinsand enations and the pattern of changes in miRNA levels was the most distinct.Conclusions: Our results have identified symptom determinants encoded by begomoviruses and show thatdevelopmental abnormalities caused by transient expression of begomovirus genes correlates with altered levels ofdevelopmental miRNAs. Additionally, all begomovirus genes were shown to modulate miRNA levels, the first timethis has been shown to be the case.BackgroundPlant virus infections may result in disease symptomsthat can include chlorosis and/or necrosis, leaf curling,altered plant stature and morphology, presumablycaused by interference with developmental processes [1].In recent years, it has been shown experimentally thatsmall RNAs (sRNAs), and particularly microRNAs (miR-NAs), play important roles in plant development andare implicated in host-pathogen interactions [2,3].Moreover, viroids that lack protein coding genes alsocause developmental abnormalities by perturbing plantgrowth by interfering with small RNAs that regulateplant development [4].miRNAs are endogenous, approx. 21nt RNAs that playimportant regulatory roles in animals and plants by tar-geting mRNA for cleavage or translational repression[5]. They are the second most abundant class of sRNAs* Correspondence: shahidmansoor7@gmail.com1 Agricultural Biotechnology Division, National Institute for Biotechnology andGenetic Engineering (NIBGE), P O Box 577, Jhang Road, Faisalabad, ILTAB,Donald, PakistanFull list of author information is available at the end of the articleAmin et al. Virology Journal 2011, 8:238http://www.virologyj.com/content/8/1/238© 2011 Amin et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative CommonsAttribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction inany medium, provided the original work is properly cited.
