Hydrogen Peroxide Accumulation and Transcriptional Changes in Grapevines Recovered from Flavescence Dorée Disease

Abstract

Flavescence dorée (FD) is considered one of the most severe phytoplasma diseases affecting grapevine. The spontaneous, complete, and stable remission of the symptoms of FD (recovery) is a phenomenon that may occur in infected grapevines. The molecular bases of this phenomenon are still unclear, although some works suggest that recovery could be linked to the accumulation of hydrogen peroxide (H2O2). Several genes coding for enzymes involved in H2O2 metabolism, in the ascorbate-glutathione cycle, defense responses, and the biosynthesis of hormones were identified. The H2O2 content was biochemically determined and the expression levels of 44 genes were analyzed through quantitative real-time reverse-transcription polymerase chain reaction in healthy (H), infected by FD-associated phytoplasma (I), and 2-years-recovered (R) plants of Vitis vinifera 'Barbera'. In tissues of R plants, large amounts of H2O2 were detected, essentially linked to an upregulation of genes involved in the production of H2O2 (germin-like protein and glycolate oxidase); whereas, in I grapevines, the overexpression of some scavenging genes reduced the quantity of H2O2. The recovery state was characterized by the activation of ethylene biosynthesis and of defense genes not linked to salicylic acid (SA) signaling, such as the WRKY2 transcription factor. Conversely, I plants reacted to phytoplasma with SA-mediated signaling, even though this response does not appear to be effective against the pathogen.

Space-Time Point Pattern Analysis of Flavescence Dorée Epidemic in a Grapevine Field: Disease Progression and Recovery

“…Overall, there was no clear correlation between the location of plants that recovered and those showing symptoms in the previous year, suggesting that plant recovery was not significantly influenced by nearby infections. Indeed, plant recovery is driven by a defense mechanism of the infected plant itself (Musetti et al, 2007; Gambino et al, 2013; Santi et al, 2013) that has no relations with the sanitary status of neighboring plants. Tracking recovered plants against newly infected plants in the following years, demonstrated that recovered plants did not reinfect over the time scale analyzed here.…”

“…Infected grapevines usually show symptoms the year after infection but longer incubation periods are possible depending on plant response to the pathogen and environmental factors (Caudwell et al, 1987). Grapevines can recover from FD disease at a rate that depends on the grapevine cultivar (Bellomo et al, 2007; Morone et al, 2007; Belli et al, 2010), but the underlying physiological and molecular mechanisms are not yet fully understood (Caudwell and Larrue, 1986; Musetti et al, 2007; Margaria and Palmano, 2011; Gambino et al, 2013; Vitali et al, 2013). In our earlier studies, we found that S. titanus could not acquire FD from asymptomatic and recovered vines (Galetto et al, 2014), and that vector acquisition efficiency was low when feeding on plants with low phytoplasma load (Bressan et al, 2005b; Galetto et al, 2016); in those experiments, it was found that recovered plants were symptomless and returned negative PCR test against FD phytoplasma (Galetto et al, 2014).…”

Metabolic and transcript analysis of the flavonoid pathway in diseased and recovered Nebbiolo and Barbera grapevines (Vitis vinifera L.) following infection by Flavescence dorée phytoplasma

“…In particular, the hormone jasmonic acid (JA) is known to be involved in regulating plant response to stress; down‐regulation of genes involved in its biosynthesis was observed in FDp‐infected grapevine leaves (Gambino et al . ). Interestingly, JA level was significantly reduced by flavonoid accumulation in Arabidopsis (Pourcel et al .…”

A germin-like protein gene of rice increased superoxide dismutase activity in transformed tobacco

“…The T 0 and T 1 transgenic plants harboring the full length cDNA of OsRGLP1 were similar to the wild-type plants in morphology; however unlike control, the six months old transgenic plants showed hypersensitive response-like necrotic lesions on older leaves when kept at day/night temperatures of 30/24 C and under direct sunlight in the absence of a challenge with any microbe. As GLPs are connected with OXO and/or superoxide dismutase activities resulting in production of H 2 O 2 (Gambino et al 2013), it was speculated that the product of OsRGLP1 may possess either one or both activities and generate H 2 O 2 resulting in hypersensitive reaction (HR)-like lesions under a high temperature and sunlight. When leaf disks from the transgenic and control plants were subjected to DAB staining, the transgenic leaf disks exhibited a higher content of H 2 O 2 .…”