Molecular and cellular aspects of Dutch elm disease

Abstract

Cet article de synthèse présente une revue des recherches concernant les interactions moléculaires et cellulaires de la maladie hollandaise de l'orme. Cette maladie, causée par le champignon Ophiostoma ulmi, provoque un flétrissement vasculaire et elle est transmise d'ormes infectés à des ormes sains par des scolytes. Des toxines fongiques sont décrites en relation avec la pathogénèse, l'une d'elles, la cérato-ulmine, étant sous investigation au niveau moléculaire, plus particulièrement en ce qui concerne son mode d 'action et sa localisation. Le champignon a aussi été examiné au niveau moléculaire pour différencier des isolats agressifs et non agressifs sur la base de profils protéiques et d'acides nucléiques. Des cartes de lien génétique sont en développement afin de corréler la perturbation de certains gènes avec la perte du pouvoir pathogène. Des antagonistes viraux et bactériens du champignon, qui peuvent être utilisés comme mécanisme de lutte biologique contre la maladie hollandaise de l'orme, ont été caractérisés ainsi que plusieurs des molécules actives intervenant dans cette lutte. Les réponses de l'hôte sont discutées aux niveaux moléculaire et biochimique, incluant les phy toalexines et les éliciteurs des mécanismes de défense. Plusieurs avenues de recherche sont discutées afin de fournir une revue des approches moléculaires visant à comprendre et à manipuler les organismes impliqués en vue du but ultime de lutter contre la maladie hollandaise de l'orme.The folio wing review gives an overview of current research in the area of molecular and cellular interactions in Dutch elm disease. This vascular wilt disease is caused by the fungus Ophiostoma ulmi and is transmitted from diseased to healthy trees by the elm bark beetles. Fungal toxins are described which are associated with pathogenesis, one of which, ceratoulmin, is under investigation at the molecular level, particularly regarding its mode of action and localization. The fungus has also been examined at the molecular level to differentiate between aggressive and non-aggressive isolates on the basis of protein and nucleic acid profiles. Genetic linkage maps are being developed to correlate disruption of certain genes with the loss of pathogenicity. Viral and bacterial antagonists of the fungus, which may serve as biological control mechanisms for Dutch elm disease, have been characterized, as have several of the active molecules responsible for control. Host responses are also discussed at the molecular and biochemical level, including phytoalexins and defense mechanism elicitors. Several Unes of investigation are discussed to provide an overview of molecular approaches to understanding and manipulating the organisms involved with the ultimate goal of controlling Dutch elm disease

Massive sequencing of Ulmus minor’s transcriptome provides new molecular tools for a genus under the constant threat of Dutch elm disease

“…Into this transcriptome, four ECs were identified in biosynthesis pathway of cutin, suberine, and wax and 15 ECs in flavonoids biosynthesis. The final products from these pathways have been described as resistance factors ( Duchesne et al, 1985 ; Sticklen et al, 1991 ; Martín et al, 2005a ). Another important pathway identified related with defense was the alpha-linolenic acid metabolism pathway that results in jasmonate biosynthesis, a plant hormone with a central role during biotic stress responses ( Santino et al, 2013 ).…”

Heritability ofUlmus minorresistance toDutch elm disease and its relationship to vessel size, but not to xylem vulnerability to drought

“…feed, they introduce fungal spores into xylem vessels. Once inside the xylem vessels, the fungus produces cell wall-degrading enzymes (Scheffer & Elgersma, 1982), toxic substances (Takai, 1974;Sticklen et al, 1991) and the hydrophobin cerato-ulmin (Takai, 1974;Van Alfen & Turner, 1975). These substances may ultimately affect sap tensile properties and could therefore be related to xylem dysfunction by embolism (Newbanks et al, 1983).…”

Avoidance by early flushing: a new perspective on Dutch elm disease research

“…Reactions taking place as a consequence of the infection may be both anatomical and chemical, and they represent a second inducible defense strategy. These reactions include blockage of vessels by tyloses, embolisms, accumulation of pectic and hemicellulosic substances (Elgersma 1982, Shigo 1982, Ouellette & Rioux 1992, Rioux et al 1998, formation of chemicals, such as phytoalexin-like sesquiterpenes (Jeng et al 1983, Duchesne et al 1985, Sticklen et al 1991, and histological barriers typically containing phenolic compounds and suberin (Rioux & Ouellette 1991a, Rioux & Ouellette 1991b, Ouellette et al 2004a, Ouellette et al 2004b, Et-Touil et al 2005.…”