Early Events Prior to Visual Symptoms in the Apoplectic Form of Grapevine Esca Disease

Abstract

Plant infection by pathogens generates various forms of symptoms. Most of them have been described as soon as they become visible, whereas preceding, discrete signs during incubation are poorly or not understood. In Vitis vinifera, esca-related pathogenic fungi inhabit living trunk wood and induce the so-called apoplexy, a sudden wilting of leaves within a few days. To further understand the apoplexy expression, the period preceding symptom appearance was investigated by following physiological and molecular markers associated with photosynthetic mechanisms and stress responses. Within the week preceding symptoms, drastic physiological alterations of photosynthesis were registered in pre-apoplectic vines, as revealed by a decrease in gas exchange, changes in chlorophyll fluorescence, and repression of photosynthesis-related genes. In the meantime, expression of defense-related genes was induced and amplified during symptom expression. Water-stress-related genes were specifically investigated because water transport may be impeded by clogging xylem vessels due to esca-causing fungi. Neither of the tested water-stress-related genes was affected in pre-apoplectic grapevine leaves whereas these genes were downregulated in drying leaves. Our results suggest that, during incubation of esca apoplexy, grapevine perceives some signals (likely fungi-originated toxins) and reacts by reducing photosynthesis and triggering defense mechanisms.

Flowering as the Most Highly Sensitive Period of Grapevine (Vitis vinifera L. cv Mourvèdre) to the Botryosphaeria Dieback Agents Neofusicoccum parvum and Diplodia seriata Infection

“…In agreement with our observation, most studies have also reported the induction of an antioxidant system (through catalytic activity, proteins expression or transcripts accumulation) on grapevine organs affected by trunk diseases (leaves [40,47,48,49]; green stem [35]; wood [36]). By scavenging the AOS formations, the plant’s antioxidant system protects against toxic oxygen intermediates [50].…”

“…Only one protein involved in responses to oxidative stresses, a thioredoxin H-type (s3015), was over-regulated in response to wounding (C2F) or fungal infection (DsF and NpF), while the abundance of a superoxide dismutase (SOD, s5018) decreased in the stem infected by Ds. Reduced expression of SOD was also reported in other organs of the vine affected by trunk diseases, green stems [35], leaves [48,49]) and trunk [36]. Similarly to the G stage, PRP-10 (s5016) and HSPs (s3014, s2123) abundance increased in the stem in response to fungal infection, particularly with Ds (Table 2).…”

Response of Vitis vinifera cell cultures to Phaeomoniella chlamydospora: changes in phenolic production, oxidative state and expression of defence-related genes

“…It has been suggested that the biphasic gene accumulation may allow the plant to adapt to a specific attack and modulate the defence response; the biphasic shape results of the consecutive expression of two types of genes: a first type quickly expressed after elicitation with a rapid degrading mRNA, followed by a second slowly expressed gene type (Wiese et al 1994). Particularly in what concerns increased expression of PAL and STSY after infection, the results here obtained in cell cultures agree with results obtained in vivo in escaaffected grapevines -in which the presence of P. chlamydospora was confirmed (Letousey et al 2010).…”

Soybean Rust: Five Years of Research

“…This may explain the high number of aquaporin encoding genes found in our fifty most down-regulated genes. On the other hand, down-regulation of genes encoding aquaporins in soybean infected by soybean rust is similar to what has been reported in esca-infected grapevine where some aquaporin encoding genes were repressed at late stages of the infection (Letousey et al, 2010). Deep sequencing allowed the analysis of expression of genes encoding proteins associated with salicylic acid (SA) biosynthesis, which is involved in defense.…”