Ferredoxin 1 is downregulated by the accumulation of abscisic acid in an ABI5‐dependent manner to facilitate rice stripe virus infection in Nicotiana benthamiana and rice

Abstract

Summary Ferredoxin 1 (FD1) accepts and distributes electrons in the electron transfer chain of plants. Its expression is universally downregulated by viruses and its roles in plant immunity have been brought into focus over the past decade. However, the mechanism by which viruses regulate FD1 remains to be defined. In a previous report, we found that the expression of Nicotiana benthamiana FD1 (NbFD1) was downregulated following infection with potato virus X (PVX) and that NbFD1 regulates callose deposition at plasmodesmata to play a role in defense against PVX infection. We now report that NbFD1 is downregulated by rice stripe virus (RSV) infection and that silencing of NbFD1 also facilitates RSV infection, while viral infection was inhibited in a transgenic line overexpressing NbFD1, indicating that NbFD1 also functions in defense against RSV infection. Next, a RSV‐derived small interfering RNA was identified that contributes to the downregulation of FD1 transcripts. Further analysis showed that the abscisic acid (ABA) which accumulates in RSV‐infected plants also represses NbFD1 transcription. It does this by stimulating expression of ABA insensitive 5 (ABI5), which binds the ABA response element motifs in the NbFD1 promoter, resulting in negative regulation. Regulation of FD1 by ABA was also confirmed in RSV‐infected plants of the natural host rice. The results therefore suggest a mechanism by which virus regulates chloroplast‐related genes to suppress their defense roles.

Tobacco mosaic virus hijacks its coat protein‐interacting protein IP‐L to inhibit NbCML30, a calmodulin‐like protein, to enhance its infection

“…In the present study, we found that IP‐L could inhibit the expression of NbCML30 at the nucleic acid and protein levels (Figure 5a–j). We speculate that on the one hand, IP‐L may induce the production of some viral siRNAs, leading to the targeted degradation of NbCML30 mRNA, or IP‐L regulates some transcription factors to inhibit the transcription of NbCML30 (Cui et al., 2021); on the other hand, IP‐L directly interacts with NbCML30 and promotes its degradation through the 26S proteasome pathway. TMV infection inhibits NbCML30 expression, and this inhibition was suppressed after IP‐L silencing (Figures 2b and 5b).…”

Cauliflower mosaic virusdisease spectrum uncovers novel susceptibility factor NCED9 inArabidopsis thaliana

“…Yet, for virus infections including CaMV, the role of ABA appears complex. Increased ABA content was measured in Nicothiana tabacum after TMV infection (Whenham et al ., 1986),in rice after Rice stripe virus infection (Cui et al ., 2021), and Cucumber mosaic virus (Alazem et al ., 2014), but not PPV infection in Arabidopsis thaliana (Pasin et al ., 2020). Further treatment with ABA increased plant resistance to Tobacco mosaic virus (Chen et al ., 2013), Plum pox virus (Pasin et al ., 2020), Chinese wheat mosaic virus (He et al ., 2021) and Bamboo mosaic virus (BaMV) in Arabidopsis (Alazem et al ., 2014) as well as reduced the lesion size in local infections of Tobacco necrosis virus (TNV) (Iriti & Faoro, 2008).…”

The effect of soil salinity and pepino mosaic virus infection on the expression of tomato defence‐related genes

“…Stress responses are highly dynamic and dependent on stress severity, as evidenced by the strikingly small overlap between transcriptome profiles under mild and severe stress in Arabidopsis (Clauw et al, 2015). Thus, under mild stress, priming-like responses might predominate, while under higher levels of salt stress, changes in ABA signalling might shift the balance towards viral susceptibility (Cui et al, 2021). This, alone, or in combination with other factors in the complex host defence network might result in the observed increase in PepMV RNA levels in plants maintained under high salinity compared to those maintained under low salinity.…”

“…ABA has been found to promote an antiviral response and induce resistance to potyviruses, either following exogenous application or in transgenic plants that overproduce ABA (Pasin et al, 2020). Another recent study, however, indicates a negative role for ABA, as its accumulation facilitates rice stripe virus infection in Nicotiana benthamiana and rice via down‐regulation of ferredoxin 1 (Cui et al, 2021). As key phytohormones act as major signalling molecules in triggering plant defence mechanisms, here, we examined the transcript levels of tomato SA‐, JA‐, ethylene (ET)‐ and ABA‐related genes under three soil salinity regimes (no‐added salt, low and high) in the absence or presence of pepino mosaic virus (PepMV), which is responsible for severe losses in tomato crops globally.…”