Significance and role of polygalacturonase production by Botrytis cinerea in pathogenesis

The saprophytic fungus Botrytis cinerea Pers.: Fr. causes serious problems in agriculture by being able to attack an extremely wide range of plants. During the infection process, different kind of cell wall-degrading enzymes are produced, among which the pectic enzymes polygalacturonases (PGs). These are supposed to play a major role in the penetration and colonization of the host tissues. This study deals with some fundamental aspects of the physiology of parasitism of B.cinerea by investigating the significance of PG production in pathogenesis.Polygalacturonase production and PG isoenzyme composition are affected by type and concentration of a pectin-related substrate. In vitro, pectic enzymes are produced in a consistent sequence always starting with the constitutively synthesized isoenzyme PG2. This isoenzyme is also present in ungerminated conidia. Both the high degree of regulation of the coordinated PG production on cell wall-related polysaccharides and its association with the ability of B.cinerea to grow on these polymers as the only carbon source, indicate that PG production is inherent to the digestion of the pectic portion of the primary cell wall.Polygalacturonase production is also dependent on the presence of inorganic phosphate. The involvement of phosphate is mediated by adenine nucleotides. Especially the synthesis of the inducible isoenzyme PG1, besides being controlled by a pectic substrate seems also to be regulated by the metabolic status of the fungus through the adenylate pool. The knowledge of the role of phosphate as an infection-stimulating compound has been applied to develop a rapid inoculation procedure, which can be adopted to screen bean cultivars for the resistance to B.cinerea and to the related weak pathogen Sclerotinia sclerotiorum.The cause of the variability in PG isoenzymatic forms between different isolates has been elucidated. When variability within a given isolate, whose origin appears to reside in the factors affecting the sequential synthesis of the PG isoenzymes, can be controlled, variability in PG patterns between different isolates is correspondingly low.The study of the biochemical and molecular properties of PG2 has shown that PG2 is an endo- enzyme whose affinity for sodium polygalacturonate is about three time higher than that for pectin, under standard conditions. The use of a new approach for the judgement of PG purity has been proposed and discussed. The physiological and biochemical properties of PG2 suggest that this enzyme could be the only PG used by B . cinerea to support the direct penetration of the primary cell wall.

Bibliographic Details

Main Author:	Leone, G.
Other Authors:	Dekker, J.
Format:	Doctoral thesis biblioteca
Language:	English
Published:	Landbouwuniversiteit Wageningen
Subjects:	botrytis cinerea, deuteromycotina, enzymes, moniliaceae, plant pathogenic fungi, enzymen, plantenziekteverwekkende schimmels,
Online Access:	https://research.wur.nl/en/publications/significance-and-role-of-polygalacturonase-production-by-botrytis
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