Insights into the control of geminiviral promoters

Abstract

Geminiviruses constitute one of the largest groups of plant viruses, having characteristic twinned geminate particles encapsidating small circular single-stranded DNA molecules. Geminiviral promoters are generally located within the intergenic region, although promoters have also been detected within the genes. Similarly, the geminivirus-associated betasatellite also harbours a promoter element for driving the expression of its only ORF. These regulatory elements of geminiviral and satellite origins have been subject of great interest to develop heterologous gene expression modules. Geminiviral promoter and regulatory elements show a complex regulation that is mediated by several host as well as viral proteins. Here, the structural and functional features of geminiviral and satellite promoters are discussed along with their regulation by plant and viral proteins. Although generalization in many cases is difficult and demands further studies, a pattern is seen to emerge on the regulation of the promoters.

Conferring DNA virus resistance with high specificity in plants using virus-inducible genome-editing system

“…We therefore developed two novel virus-inducible CRISPR/Cas9 systems in which the expression of Cas9 is controlled in terms of location and time to reduce off-target effects (Fig. 1 b), since the expression of intergenic regions (promoters) containing conserved cis elements in the geminiviruses genome can be inducibly regulated by the viruses themselves [ 20 – 22 ]. To construct a virus-inducible genome-editing (VIGE) system, we selected two beet severe curly top virus (BSCTV)-inducible promoters (pV86 and pC86) [ 20 ] and tested their inducibility in a transient system in Nicotiana benthamiana plants.…”

“…Previous research has shown that virus-responsive promoters exist in a range of geminivirus genomes with the tight control under the viral proteins upon infection, and no evidence has been found on the induction of these promoters by other virus-unrelated conditions [ 20 – 22 ]. Thus, the virus inducible genome-editing system developed in this research should be widely applicable to defend plants against a variety of geminiviruses.…”

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

“…On the basis of pairwise sequence identities, genome organization (monopartite or bipartite), host range (monocot or dicot) and insect vector ( phloem-feeding homopteran insects such as aphids, leafhoppers, treehoppers or whiteflies), this family is subdivided into nine genera [2]. Geminiviruses code for 4-7 open reading frames (ORFs) through the generation of multiple overlapping transcripts, which are under the tight regulation of bidirectional viral promoters located within their intergenic region (IR) [3]. Proteins encoded in the complementary-strand of the monopartite DNA A genome are involved in virus replication, control of gene expression and suppression of the host's defence machinery.…”

Localization of Tobacco Yellow Dwarf Virus Replication Using the In Plant Activation (INPACT) Expression Platform

“…The virus encodes four proteins, a movement protein (MP), and coat protein (CP) in the virion sense and Replication (Rep) and Replication A (RepA) proteins in the complementary sense. Only Rep is essential for virus replication, however, mastrevirus RepA proteins have been shown to interact with and functionally inhibit a plant-encoded Retinoblastoma-like protein, creating a cellular environment permissive to the RCR process by which these viruses propagate [20,21]. A large intergenic region contains a stem and nonanucleotide loop structure, the origin of first strand synthesis for RCR, and transcription initiation elements for bidirectional expression of virion and complementary sense genes [20].…”