The roles of ascorbic acid and glutathione in symptom alleviation to SA-deficient plants infected with RNA viruses

Abstract

Salicylic acid (SA) is required for plant systemic acquired resistance (SAR) to viruses. However, SA-deficient plants adapt to RNA virus infections better, which show a lighter symptom and have less reactive oxygen species (ROS) accumulation. The virus replication levels are higher in the SA-deficient plants during the first 10 days, but lower than the wild-type seedlings after 20 dpi. The higher level of glutathione and ascorbic acid (AsA) in SA-deficient plants may contribute to their alleviated symptoms. Solo virus-control method for mortal viruses results in necrosis and chlorosis, no matter what level of virus RNAs would accumulate. Contrastingly, early and high-dose AsA treatment alleviates the symptom, and eventually inhibits virus replication after 20 days. ROS eliminators could not imitate the effect of AsA, and could neither alleviate symptom nor inhibit virus replication. It suggests that both symptom alleviation and virus replication control should be considered for plant virus cures.

Expression of a GDP-L-galactose phosphorylase-like gene in a Chinese wild Vitis species induces responses to Erysiphe necator and defense signaling molecules

“…Moreover, AsA content also increased in mycorrhizal strawberry after pathogen inoculation (Li et al, 2010b). Early and high-dose AsA treatment alleviates the symptoms of SA-deficient plants, and eventually inhibits RNA virus replication after 20 days (Wang et al, 2011a). In the present study, the AsA concentration of E. necator-inoculated leaves showed different tendencies in the resistant genotype 'Baihe-35-1' and the susceptible genotype 'Hunan-1' (Figure 6).…”

“…Application of Eth increased AsA concentrations in apple peel and meiwa kumquat skin or flesh (Burden and Bramlage, 1994;Kondo et al, 2005). The higher levels of glutathione and AsA observed in SA-deficient plants may contribute to their alleviated symptoms (Wang et al, 2011a). In contrast, other studies have shown that these signaling molecules have no effect on AsA content (Keramat et al, 2009;Gergoff et al, 2010;Krajnc et al, 2011), suggesting that the effects of signaling molecules on AsA accumulation differ between species.…”

“…(2011a) confirmed that this enhanced resistance could be eliminated by 0.5 mM AsA treatment and that under a high-dose 5 mM AsA treatment, VTC1 and wild-type plants display similar phenotypes. It was further suggested that symptom alleviation by high-dose AsA treatment and by AsA deficiency might be accomplished by different mechanisms (Wang et al, 2011a). This may result from the signaling role of pathogen-induced ROS in AsA-deficient Arabidopsis mutants, which results in the programmed cell death, i.e., hypersensitive response of plants against invading pathogens.…”

“…Low AsA concentrations in VTC1 activated expression of SA-regulated genes; a response found to be dependent on the natriuretic peptide receptor A/ guanylate cyclase A (Brosché and Kangasjärvi, 2012). However, the enhanced resistance of VTC1 was also found to be prevented by a 0.5-mM AsA treatment, which also resulted in similar phenotypes between VTC1 and wild-type plants (Wang et al, 2011a). Moreover, Davey et al (2007) showed that AsA content increased after pathogen inoculation.…”

The higher expression levels of dehydroascorbate reductase and glutathione reductase in salicylic acid-deficient plants may contribute to their alleviated symptom infected with RNA viruses

“…Superoxide and H 2 O 2 staining and cell-death determination indicated that they accumulated less ROS. 7 Virus replication levels were higher in the SA-deficient plants, than in Col-0 or Cvi-0 wild-type seedlings during the first 10 days after inoculation (dpi) suggesting the role of SA in innate immunity. However, for the long-term infections (more than 20 days), the less-severe symptoms in SA-deficient plants may eventually resulted in inhibition of viral multiplication.…”