Synergistic infection of BrYV and PEMV 2 increases the accumulations of both BrYV and BrYV-derived siRNAs in Nicotiana benthamiana

Abstract

Viral synergism is caused by co-infection of two unrelated viruses, leading to more severe symptoms or increased titres of one or both viruses. Synergistic infection of phloem-restricted poleroviruses and umbraviruses has destructive effects on crop plants. The mechanism underlying this synergy remains elusive. In our study, synergism was observed in co-infections of a polerovirus Brassica yellows virus (BrYV) and an umbravirus Pea enation mosaic virus 2 (PEMV 2) on Nicotiana benthamiana, which led to (1) increased titres of BrYV, (2) appearance of severe symptoms, (3) gain of mechanical transmission capacity of BrYV, (4) broader distribution of BrYV to non-vascular tissues. Besides, profiles of virus-derived small interfering RNAs (vsiRNAs) from BrYV and PEMV 2 in singly and doubly infected plants were obtained by small RNA deep sequencing. Our results showed that accumulation of BrYV vsiRNAs increased tremendously and ratio of positive to negative strand BrYV vsiRNAs differed between singly infected and co-infected plants. Positions to which the BrYV vsiRNAs mapped to the viral genome varied considerably during synergistic infection. Moreover, target genes of vsiRNAs were predicted and annotated. Our results revealed the synergistic characteristics during co-infection of BrYV and PEMV 2, and implied possible effects of synergism have on vsiRNAs.

Genome-wide identification of the Dicer-like family in cotton and analysis of the DCL expression modulation in response to biotic stress in two contrasting commercial cultivars

“…It has been also previously demonstrated that DCL4 can downregulate DCL2 expression [56]. [66]. These results are in agreement with our previous findings [51,54] It should take in account, however, that ours results to not exclude that other CLRDV-resistance mechanisms not directly related to DCL2/4 modulation should be active in DO plants.…”

The Conserved Proline18 in the Polerovirus P3a Is Important for Brassica Yellows Virus Systemic Infection

“…Brassica yellows virus (BrYV) is a tentative species in the genus Polerovirus . Viruses in this genus and Luteovirus are limited to the phloem and transmitted by aphid ( King et al, 2012 ; Zhou et al, 2017 ). BrYV is distributed widely in mainland China, as well as in South Korea and Japan ( Xiang et al, 2011 ; Zhang et al, 2014 ; Lim et al, 2015 ; Kamitani et al, 2016 ).…”

“…For convenience of the virus research, the full-length infectious cDNA clones of BrYVs were constructed under control of the cauliflower mosaic virus 35S promoter ( Zhang et al, 2015 ). As the BrYV is a phloem-restricted virus, an umbravirus Pea enation mosaic virus 2 (PEMV 2) can help BrYV to be mechanically transmitted and invade non-vascular tissue in Nicotiana benthamiana ( Zhou et al, 2017 ).…”

Identification, Characterization and Full-Length Sequence Analysis of a Novel Polerovirus Associated with Wheat Leaf Yellowing Disease

“…Therefore, it is assumed that DCL2 and DCL4 likely play important role in generating WLYaV siRNAs whereas in most viruses and viroids, the 21 nt species is the predominant class (Donaire et al, 2009 ; Ma et al, 2011 ; Li et al, 2012 ; Zhang et al, 2014 ). For poleroviruses such as cotton leafroll dwarf virus, MaYMV, and brassica yellows virus, the abundant vsiRNA class is 22 nt (Silva et al, 2011 ; Chen et al, 2016 ; Zhou et al, 2017 ). This suggests that these poleroviruses and WLYaV may affect DCL4 activity which is then compensated by DCL2.…”