The Endopolygalacturonase 1 from Botrytis cinerea Activates Grapevine Defense Reactions Unrelated to Its Enzymatic Activity

Abstract

A purified glycoprotein from Botrytis cinerea (strain T4), identified as endopolygalacturonase 1 (T4BcPG1) by mass spectrometry analysis, has been shown to activate defense reactions in grapevine (Vitis vinifera cv. Gamay). These reactions include calcium influx, production of active oxygen species, activation of two mitogen-activated protein kinases, defense gene transcript accumulation, and phytoalexin production. Most of these defense reactions were also activated in grapevine in response to purified oligogalacturonides (OGA) with a degree of polymerization of 9 to 20. In vivo, these active OGA might be a part of the released products resulting from endopolygalacturonase activity on plant cell walls. Nevertheless, the intensity and kinetics of events triggered by OGA were very different when compared with T4BcPG1 effects. Moreover, chemical treatments of T4BcPG1 and desensitization assays have allowed us to discriminate enzymatic and elicitor activities, indicating that elicitor activity was not due to released oligogalacturonides. Thus, BcPG1 should be considered as both an avirulence and a virulence factor. The role of the secreted BcPG1 in the pathogenicity of Botrytis cinerea is discussed.

Regulation of stilbene biosynthesis in plants

“…release from the internal stores, regulation of Ca 2? fluxes across the plasma membrane, variations in plasma membrane potential, reactive oxygen species (ROS) production, activation of mitogen-activated protein kinases (MAPK), up-regulation of PAL and STS expression, and increased stilbene production levels (Poinssot et al 2003;Vandelle et al 2006 Belchí-Navarro et al (2013b), the MeJA-or CDs-induced resveratrol biosynthesis was partially dependent on Ca 2? release from internal stores.…”

Arabidopsis Defense against Botrytis cinerea: Chronology and Regulation Deciphered by High-Resolution Temporal Transcriptomic Analysis

“…Polygalacturonase (PG) is another component of B. cinerea that is essential for virulence and detected by the plant. PG is detected via at least two different mechanisms; one through its ability to function as a MAMP with the presence of the protein (independent of its enzymic activity) activating defense responses in the host (Poinssot et al, 2003). Additionally, PGs act on the host cell wall to degrade pectin, the primary carbon source for the pathogen, producing oligogalacturonides (OGs).…”

Fungal Endopolygalacturonases Are Recognized as Microbe-Associated Molecular Patterns by the Arabidopsis Receptor-Like Protein RESPONSIVENESS TO BOTRYTIS POLYGALACTURONASES1

“…Indeed, infiltrating BcPG2 into broad bean leaves or transient expression of BcPG2 in Nicotiana benthamiana led to tissue collapse and necrosis, and the necrotic response was abolished when the catalytic domain of the PG was mutated (Kars et al, 2005;Joubert et al, 2007). By contrast, Poinssot et al (2003) reported that BcPG1 can activate plant defense responses in grapevine (Vitis vinifera) cell suspensions independently of its enzymatic activity, suggesting that the protein itself might be recognized by plant cells as an elicitor. These studies with seemingly opposing conclusions were conducted with different isozymes on distinct cell types of different plant species.…”