MOLECULAR CHARACTERIZATION OF A BEGOMOVIRUS ASSOCIATED WITH CLERODENDRON INERME

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About Authors:
Sanjay Kumar Yadav*1, Anjana Yadav1, Shahana Majumder2
*1Dept of Pharmaceutical Chemistry, B.B.S. Institute of Pharmaceutical & Allied Sciences, Greater Noida, (U.P.), India
1Dept of Biotechnology, Chhatrapati Sahu Ji Maharaj University, Kanpur, (U.P.), India
2Dept of Biotechnology, Sharda University, School of Engineering and Technology,
Greater Noida, (U.P.), India
*sanjay_yadav3333@yahoo.co.in

ABSTRACT
Viruses are pathogens with an extremely narrow host range. Their phylogenetic origin is vague, tough it has always been considered that viruses are genes that became vagrant after having excluded themselves of the host’s or a related species’ genome (Anderson et.al., 2004). Viruses are usually units consisting of nucleic acids and coat proteins called capsids. Viroids consist only of RNA, i.e. they contain no protein at all. Except for a few cases, Viruses have no energy metabolism of their own. Consequently, they cannot perform syntheses and are thus unable to replicate themselves. Depending on their host species, it is distinguished between plant viruses multiplying almost exclusively within plant cells, bacterial viruses (bacteriophages) that depend on living bacteria, and animal viruses. The genetic information of viruses is either encoded by single-stranded RNA (Most plant viruses), double-stranded RNA (Wound tumor viruses), single-stranded DNA (Gemini viruses) or double stranded DNA (Cauliflower mosaic virus). Based on the shape of the viruses particle, it is distinguished between rod shaped and icosahedral viruses with a capsid that seem almost spherical. Viruses’ cause many disease in humans of international importance for example  smallpox polio, hepatitis etc. viruses cause also many important plant disease and are responsible for huge loss in crop production and quality in all part of the world. Around 25 years ago, when genomic properties of geminiviruses were studied, many scientists regarded them as ‘friends of humans’, because of their  potential as gene transfer vectors in plant genetic engineering and non-harmful effects on host plants. But far from being friends, these viruses have now emerged as foes and are a serious threat to world agriculture now. Increase in international commodity trade, intercontinental transportation networks and a changing global climate have contribute to the spread of this virus and its whitefly vector (Moffat et.al.,1999).

Reference Id: PHARMATUTOR-ART-1377

INTRODUCTION
Plant viruses are divided into more than 15 families, of which Geminiviridae constitutes the second largest family after the Potyviridae besides their importance as plant pathogens. Gemini viruses are ideal models for the study of replication and gene expression in plants, due to the fact that they replicate in the cell nucleus via a dsDNA molecule1. Such studies have generated a large amount of information regarding the molecular biology of geminiviruses. Gemini viruses are characterized by their twin geminate particles, ssDNA circular genomes and whitefly (Bemisia tabaci) mediated transmissibility. Geminiviridae is represented by four genera namely Mastrevirus, Curtovirus, Topocuvirus and Begomovirus2. The genus Begomovirus is the largest and consists of more than 180 species and several unassigned isolates. Begomoviruses is the largest genus of the family of single stranded DNA plant viruses and contains whitefly- transmitted geminiviruses that infect dicotyledonous plant Particle of Gemini viruses are quasi-isometric and they are usually found in pair , hence the name ‘Gemini’3. Symptoms vary from mosaic, yellow leaf, curling, rolling of leaves, thickening of veins, reduction of fruit set, yellow mottling, crinkling, severe stunting, reduced yields and at times death of plants. On infection typical mosaic-like leaf patterns of light and dark green occur4.They are causal agent of some of most devastating plant leaf curls in cotton, pepper and tomatoes, mosaic and yellow mosaic of cassava, pulses and beans. During severe infection,India virus Munbean yellow mosaic virus (MYMIV) and Tomato leaf curl virus (ToLCV) can damage up to 70% and 100% of yield respectively5. The Gemini viruses can be found throughout the subtopic and tropic including Central America and the Caribbean. Year after year in the early 1990s, for example, Gemini viruses destroyed up to 95% of the tomato harvest in the Dominican Republic, and in just the 1991-92 growing season in Florida, they caused $140 million in damage to the tomato crop6. With the virus continuing to spread and other control measures, such as insecticides falling short, plant genetic engineers are struggling to create resistant plants. So far they have had no lasting successes, although they do have promising leads. The viruses have also struck in the Caribbean in the early 1990, the first serious Gemini viruses infections appeared in Florida & Texas in the united state at about the same time7,8,9. As is evident that a begomovirus has immense economic implications and owing to its easy availability it was selected as the candidate for our research project10.

MATERIALS AND METHODS
A range of techniques can be used to detect and identify Gemini viruses based on enzymatic analysis, biochemical analysis, and PCR based analysis11.
Different methods are:
a.       Protein based – immunological tests, ELISA, DOT BLAST.
b.      Genome based – PCR.
c.       Microscopy based – protein immune assay, fluorescence based assay.

Host Plant chosen
The plant species selected for research is Clerodendron inerme (family Verbenaceae) a commonly used hedge plant.C. inerme is valued in landscaping as a groundcover or hedge plant. It has attractive evergreen foliage and fragrant white flowers that form in clusters and are accented by delicate red protruding stamens. Seaside Clerodendron, as its name suggests, grows well along the beach tolerating the salt spray of the ocean and the harsh rays of the sun. It is a versatile plant and can be grown as topiary or as a bonsai. Clerodendron plants growing inand around the university campus at Greater Noida, UP, Indiawhen surveyed  was found to be showing yellow mosaic, bright yellow spots along the midrib which coalesce to give  mosaic, reduction in leaf size, and stunting of the plant. Soit was imperative to diagnose and investigate the causal agent12.

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