Enhanced nicking activity of Rep in presence of pre-coat protein of Mungbean yellow mosaic India virus

Plant-virus-insect tritrophic interactions: insights into the functions of geminivirus virion-sense strand genes

The genome of the plant-infecting viruses in the family Geminiviridae is composed of one or two circular single stranded DNA of approximately 2.7-5.2 kb in length. These viruses have emerged as the most devastating pathogen infecting a large number of crops and weeds across the continents. They code for fewer open reading frames (ORFs) through the generation of overlapping transcripts derived from the bidirectional viral promoters. Members of geminiviruses code for up to four ORFs in the virion-sense strand, and their gene expression is regulated by various cis-elements located at their promoters in the intergenic region. These viral proteins perform multiple functions at every stage of the viral life cycle such as virus transport, insect-mediated virus transmission and suppression of host defence. They impede the host's multi-layered antiviral mechanisms including gene silencing (at transcriptional and post-transcriptional levels) and hypersensitive response. This review summarizes the essential role of virion-sense strand encoded proteins in transport of viral genomes within and between plant cells, countering defence in hosts (both plants and the insects), and also in the ubiquitous role in vector-mediated transmission. We highlight the significance of their pro-viral activities in manipulating host-derived innate immune responses and the interaction with whitefly-derived proteins. We also discuss the current knowledge on virus replication and transcription within the insect body.

Involvement of host regulatory pathways during geminivirus infection: a novel platform for generating durable resistance

Geminiviruses are widely distributed throughout the world and cause devastating yield losses in almost all the economically important crops. In this review, the newly identified roles of various novel plant factors and pathways participating in plant–virus interaction are summarized with a particular focus on the exploitation of various pathways involving ubiquitin/26S proteasome pathway, small RNA pathways, cell division cycle components, and the epigenetic mechanism as defense responses during plant–pathogen interactions. Capturing the information on these pathways for the development of strategies against geminivirus infection is argued to provide the basis for new genetic approaches to resistance.

Replication of Plant Viruses

Viruses replicate using both their own genetic information and host cell components and machinery. The different genome types have different replication pathways which contain controls on linking the process with translation and movement around the cell as well as not compromising the infected cell. This chapter discusses the replication mechanisms, faults in replication and replication of viruses co-infecting cells.

Viruses replicate using both their own genetic information and host cell components and machinery. The different genome types have different replication pathways which contain controls on linking the process with translation and movement around the cell as well as not compromising the infected cell. This chapter discusses the replication mechanisms, faults in replication and replication of viruses coinfecting cells.

Begomovirus research in India: a critical appraisal and the way ahead

Begomoviruses are a large group of whitefly-transmitted plant viruses containing single-stranded circular DNA encapsidated in geminate particles. They are responsible for significant yield losses in a wide variety of crops in India. Research on begomoviruses has focussed on the molecular characterization of the viruses, their phylogenetic analyses, infectivities on host plants, DNA replication, transgenic resistance, promoter analysis and development of virus-based gene silencing vectors. There have been a number of reports of satellite molecules associated with begomoviruses. This article aims to summarize the major developments in begomoviral research in India in the last approximately 15 years and identifies future areas that need more attention.