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

Abstract

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.

Differences in the 3’ intergenic region and the V2 protein of two sequence variants of tomato curly stunt virus play an important role in disease pathology in Nicotiana benthamiana

“…Since the 3’ IR contains the promoter regions driving expression of downstream vs genes, as well as cis -acting elements involved in regulating their transcription [ 23 , 24 ] any sequence differences in this region may result in differential expression of vs ORFs in V30- and V22-infected plants. Quantitative RT-PCR should be conducted to determine if V1/V2 transcript levels differ between the two wild types as well as selected IR-swap mutants.…”

Circular Single-Stranded DNA: Discovery, Biological Effects, and Applications

“…In geminiviruses, the first difference is that they initiate infection though the different hemipterous insects, which keep the primary target of viruses as differentiated cells. − Most viruses cannot replicate in these host insect cells, but Pakkianathan et al reported for the first time that the single-stranded DNA plant virus-like Tomato yellow leaf curl virus (TYLCV) can replicate in its whitefly vector. Whether in plant cells or insect cells, there is a huge challenge of transporting CssDNA into the nucleus.…”

“…As for the CssDNA genome of geminivirus, plants also have evolved various resistance strategies. , In plants, DNA methylation is an important epigenetic marker and can be used to check virus infection . It may be evaded by viral DNA methylation during the ss-to-ds process, but the plants containing the resistance gene like Try-1 were identified to use plant-specific, RNA-directed DNA methylation pathway leading to viral transcriptional gene silencing (TGS) .…”

Silencing suppressors of rice black‐streaked dwarf virus and rice stripe virus hijack the 26S proteasome of Laodelphax striatellus to facilitate virus accumulation and transmission

“…Numerous insect vectors have evolved multiple defense response mechanisms to resist virus infection 23–25 . Ubiquitin/26S proteasome (UPS) pathway is the major proteolytic machinery found in eukaryotes and is responsible for the degradation of substrates targeted specifically by polyubiquitin modification 26,27 .…”