Enzymatic interactions between Gremmeniella abietina var. abietina, European race, and two resistant hosts, Pinus banksiana and P. contorta

Abstract

Summary Ultrastructural observations showed that the European race of Gremmeniella abietina var. abietina can secrete several cell wall–degrading enzymes that help the invasion of Pinus banksiana and P. contorta shoot tip tissues. Alterations in the content or distribution of cellulose were obvious, indicating that colonization might be achieved primarily through the action of glucanases. Polygalacturonases seemed more abundant in the cortex and the phloem of the stem, suggesting they are among the first enzymes secreted by the pathogen during infection. Production of laccases and peroxidases was also revealed but always close to fungal cells or in areas where host wall degradation was obvious. In places where there was an accumulation of phenolic compounds in the infected zones of the shoot, particularly in or near the transition zone, immunolocalization of both enzymes was limited or absent. Laccases and polygalacturonases were regularly detected over the extracellular sheath of G. abietina, and this indicates that the sheath could play a significant role during host wall degradation. Finally, examination of G. abietina wall constituents, such as chitin and β‐1,3‐glucans, suggests that the composition of the pathogen wall changes during the infection process. This change may be associated with the secretion of fungal enzymes but could also be linked to host reactions altering the integrity of pathogen cell walls.

Aleppo pine provenances vary in susceptibility and secondary chemical response toGremmeniella abietinainfection

“…Regarding G. abietina infections, both physical and chemical reactions in inoculated trees have been reported in previous studies. According to these previous studies, the host's resistance to G. abietina infection is likely to be related to: (i) production of ligno‐suberized tissues that help the tree compartmentalize the invaded tissues, and (ii) secretion of molecules such as phenolic compounds capable of degrading or altering the extracellular sheath of the pathogen, which contains chitin, galactose, proteins and lipids (Simard et al ., , ; Laflamme et al ., ; Bernhold et al ., ). Nevertheless, to the authors' knowledge, there are no studies comparing the concentration of phenolic compounds in trees showing differential susceptibility to G. abietina infections.…”

Pool of endoglucanase genes in Schizophyllum commune Fr.:Fr. (Basidiomycetes) on the territory of Ukraine

“…All processes of destruction of the plant cell wall take place with involvement of various fungal enzyme systems, therefore, these are highly favored targets of mycological (Floudas et al 2012(Floudas et al , 2015Rytioja et al 2014) and phytopathological research (Przybył et al 2006;Simard et al 2013). Certain fungi cause a transition type of decay (Redhead and Ginns 1985).…”