Identification and characterization of a new geminivirus from soybean plants and determination of V2 as a pathogenicity factor and silencing suppressor

Abstract

Background Soybean is one of the four major crops in China. The occurrence of viruses in soybean causes significant economic losses. Results In this study, the soybean leaves from stay-green plants showing crinkle were collected for metatranscriptomic sequencing. A novel geminivirus, tentatively named soybean geminivirus A (SGVA), was identified in soybean stay-green plants. Sequence analysis of the full-length SGVA genome revealed a genome of 2762 nucleotides that contain six open reading frames. Phylogenetic analyses revealed that SGVA was located adjacent to the clade of begomoviruses in both the full genome-based and C1-based phylogenetic tree, while in the CP-based phylogenetic tree, SGVA was located adjacent to the clade of becurtoviruses. SGVA was proposed as a new recombinant geminivirus. Agroinfectious clone of SGVA was constructed. Typical systemic symptoms of curly leaves were observed at 11 dpi in Nicotiana benthamiana plants and severe dwarfism was observed after 3 weeks post inoculation. Expression of the SGVA encoded V2 and C1 proteins through a potato virus X (PVX) vector caused severe symptoms in N. benthamiana. The V2 protein inhibited local RNA silencing in co-infiltration assays in GFP transgenic 16C N. benthamiana plants. Further study revealed mild symptoms in N. benthamiana plants inoculated with SGVA-ZZ V2-STOP and SGVA-ZZ V2-3738AA mutants. Both the relative viral DNA and CP protein accumulation levels significantly decreased when compared with SGVA-inoculated plants. Conclusions This work identified a new geminivirus in soybean stay-green plants and determined V2 as a pathogenicity factor and silencing suppressor.

Transcriptional profiling reveals a critical role of GmFT2a in soybean staygreen syndrome caused by the pest Riptortus pedestris

“…Type II plants have leaf crinkling, and plants may sometimes be stunted. Recent studies describing a new geminivirus that is associated with soybean staygreen syndrome (Cheng et al ., 2022; Li et al ., 2022; Wang et al ., 2022) report field samples consistent with type II symptoms (Cheng et al ., 2022). Our previous studies showed that in addition to this geminivirus, type II plants may also be coinfected with other viruses, including cowpea mild mottle virus and soybean mosaic virus (Wei et al ., 2021).…”

Leafhopper transmits soybean stay-green associated virus to legume plants

“…Six viral genomic sequences (MT221447.1, OM914609.1, OL404964.1, OL855975.1, OM145986.1, and MZ505080.1) were obtained from NCBI. Although they were named differently [27–29], they all belong to the species termed SoSGV in this and the former study [13]. The 6 sequences were aligned with the 22 genomic sequences obtained in this study using MAFFT (version 7.475).…”

“…Recently, a novel geminivirus, soybean stay-green associated virus (SoSGV) [13], has been identified and found to be strongly associated with the SGS incidences in the Huang-Huai-Hai region of China [13, 27–29]. Inoculation of this virus to soybean plants based on an infectious viral clone recapitulates the SGS symptoms, like increased flat pod number and reduced yield, while the total pod number keeps unchanged [13].…”

Understandings and future challenges in soybean functional genomics and molecular breeding

“…Although they referred to them by different names, the viruses in these studies had the same genome length and structure, and two viruses had more than 98% sequence similarity. Furthermore, Li et al (2022c) identified the V2 open reading frame as the pathogenicity factor and silencing suppressor. Taken together, R. pedestris might be the vector of virus that causes soybean staygreen syndrome, which needs further study, and resistant cultivars are needed to overcome this serious disease.…”