Roles of two distinct alphasatellites modulating geminivirus pathogenesis

Abstract

Background Alphasatellites are small coding DNA satellites frequently associated with a begomovirus/betasatellite complex, where they are known to modulate virulence and symptom development. Two distinct alphasatellites, namely, Cotton leaf curl Multan alphasatellite (CLCuMuA), and Gossypium darwinii symptomless alphasatellite (GDarSLA) associated with Cotton leaf curl Multan virus-India (CLCuMuV-IN) and Ludwigia leaf distortion betasatellite (LuLDB) were found to be associated with yellow mosaic disease of hollyhock (Alcea rosea) plants. In this study, we show that alphasatellites CLCuMuA and GDarSLA attenuate and delay symptom development in Nicotiana benthamiana. The presence of either alphasatellites reduce the accumulation of the helper virus CLCuMuV-IN. However, the levels of the associated betasatellite, LuLDB, remains unchanged. These results suggest that the alphasatellites could contribute to the host defence and understanding their role in disease development is important for developing resistance strategies. Methods Tandem repeat constructs of two distinct alphasatellites, namely, CLCuMuA and GDarSLA associated with CLCuMuV-IN and LuLDB were generated. N. benthamiana plants were co-agroinoculated with CLCuMuV and its associated alphasatellites and betasatellite molecules and samples were collected at 7, 14 and 21 days post inoculation (dpi). The viral DNA molecules were quantified in N. benthamiana plants by qPCR. The sequences were analysed using the MEGA-X tool, and a phylogenetic tree was generated. Genetic diversity among the CLCuMuA and GDarSLA was analysed using the DnaSP tool. Results We observed a reduction in symptom severity and accumulation of helper virus in the presence of two alphasatellites isolated from naturally infected hollyhock plants. However, no reduction in the accumulation of betasatellite was observed. The phylogenetic and genetic variability study revealed the evolutionary dynamics of these distinct alphasatellites , which could explain the role of hollyhock-associated alphasatellites in plants. Conclusions This study provides evidence that alphasatellites have a role in symptom modulation and suppress helper virus replication without any discernible effect on the replication of the associated betasatellite.

Patterns of Genetic Diversity among Alphasatellites Infecting Gossypium Species

“…The presence of 12 different alphasatellites in association with cotton leaf curl geminiviruses is an interesting phenomenon despite their non-essential role in disease etiology [ 9 ]. In the Old World, the role of alphasatellites has been elucidated as the suppression of gene silencing [ 15 , 16 ], and they attenuate disease symptoms [ 17 , 18 , 19 ]. Recent experiments conducted on New World alphasatellites [ 12 , 14 ] have suggested that their presence can increase the severity of symptoms.…”

“…Old World geminialphasatellites play a role in the suppression of gene silencing at the transcriptional and post-transcriptional levels [ 14 , 15 , 16 ]. They have also been reported to attenuate the symptoms caused by helper viruses [ 17 , 18 , 19 ]. The experiments conducted on NW alphasatellites revealed that they increased disease severity while negatively affecting viral transmission by Bemicia tabaci [ 12 ].…”

Development of Stable Infectious cDNA Clones of Tomato Black Ring Virus Tagged with Green Fluorescent Protein

“…Hence, infectious clones are a source of virus RNA/DNA that is able to replicate, infect, and spread in the host. Since 1984, when the first RNA infectious clone was established (developed for brome mosaic virus, BMV) [ 1 ] a variety of plant viruses from different families, such as Potyviridae [ 2 , 3 , 4 , 5 ], Virgaviridae [ 6 , 7 , 8 , 9 ], Luteoviridae [ 10 , 11 , 12 ], Secoviridae [ 13 , 14 , 15 ], Geminiviridae [ 16 ], and many others, have been reconstituted from their infectious clones. Using the constructs, combined with site-directed mutagenesis and an efficient inoculation method (RNA transcripts or agroinoculation), provides numerous opportunities to assay the biological activity and functionality of the studied viruses [ 17 ].…”

“…Tomato black ring virus (TBRV) is a member of the Nepovirus genus (subgroup B) in the family Secoviridae, which infects over 90 species, including important crops, berry fruits, ornamental, herbaceous, and woody plants [18]. On infected host plants, the TBRV causes Viruses 2024, 16, 125 2 of 13 mosaic or necrosis on the leaves, with the most characteristic symptoms of necrotic rings on the leaves and fruits. The virus can be easily transmitted mechanically by nematodes (Longidorus attenuates, L. elongatus) and through seeds, which promotes the dissemination of the virus over long distances [18,19].…”

Geminiviridae and Alphasatellitidae Diversity Revealed by Metagenomic Analysis of Susceptible and Tolerant Tomato Cultivars across Distinct Brazilian Biomes

“…Promoter regions (homologous to the ones of the CPs from New World begomoviruses) display nearly palindromic DNA sequences with a conserved core (ACTT–N7–AAGT), which is distinct from that of the Old World begomoviruses [ 14 ]. Some begomoviruses also present associations with DNA satellites, which can either attenuate or intensify the symptom expression depending on the relationship between the satellite and its helper virus [ 15 , 16 , 17 ].…”