The Protein Disulfide Isomerase of Botrytis cinerea: An ER Protein Involved in Protein Folding and Redox Homeostasis Influences NADPH Oxidase Signaling Processes

Abstract

Botrytis cinerea is a filamentous plant pathogen, which infects hundreds of plant species; within its lifestyle, the production of reactive oxygen species (ROS) and a balanced redox homeostasis are essential parameters. The pathogen is capable of coping with the plant’s oxidative burst and even produces its own ROS to enhance the plant’s oxidative burst. Highly conserved NADPH oxidase (Nox) complexes produce the reactive molecules. The membrane-associated complexes regulate a large variety of vegetative and pathogenic processes. Besides their commonly accepted function at the plasma membrane, recent studies reveal that Nox complexes are also active at the membrane of the endoplasmic reticulum. In this study, we identified the essential ER protein BcPdi1 as new interaction partner of the NoxA complex in B. cinerea. Mutants that lack this ER chaperone display overlapping phenotypes to mutants of the NoxA signaling pathway. The protein appears to be involved in all major developmental processes, such as the formation of sclerotia, conidial anastomosis tubes and infection cushions (IC’s) and is needed for full virulence. Moreover, expression analyses and reporter gene studies indicate that BcPdi1 affects the redox homeostasis and unfolded protein response (UPR)-related genes. Besides the close association between BcPdi1 and BcNoxA, interaction studies provide evidence that the ER protein might likewise be involved in Ca2+ regulated processes. Finally, we were able to show that the potential key functions of the protein BcPdi1 might be affected by its phosphorylation state.

The Subtilisin-Like Protease Bcser2 Affects the Sclerotial Formation, Conidiation and Virulence of Botrytis cinerea

“…In M. oryzae, knockout of an important subtilisin-like serine protease-encoding gene, spm1, also resulted in a defect in appressorium formation as well as in infectious growth at the post-penetration stage [34]. A number of genes have been reported to be involved in infection structure formation, thereby affecting the full virulence of B. cinerea [31,39,[42][43][44]. In this study, we found that deletion of Bcser1 had no effect on the formation of infection cushions in B. cinerea.…”

A novel Botrytis cinerea‐specific gene BcHBF1 enhances virulence of the grey mould fungus via promoting host penetration and invasive hyphal development

“…Although our data indicated that loss of BcHBF1 did not impair germination of the mutant sclerotia, the effect of BcHBF1 on sexual production via sclerotial spermatization remains to be clarified. Many B. cinerea factors that are critical for B. cinerea sclerotial formation have been recently characterized, including diacylglycerol O‐acyl transferase 2 (DGAT2) (Sharma et al ., ), autophagy‐related proteins (Liu et al ., ; Ren et al ., , ), the kynurenine 3‐monooxygenase (Kang et al ., ), the essential ER protein BcPdi1 (Marschall and Tudzynski, ), and the MADS‐Box transcription factor Bcmads1 (Zhang et al ., ). BcHbf1, together with these above‐mentioned factors, share a common in controlling the pathogen sclerotial formation; however, the association of these factors that are critical for the production of sclerotia remains obscure, and the clarification of the connection of these crucial factors for sclerotial production may constitute an intriguing research direction in the pathogen development.…”

Signal peptide peptidase activity connects the unfolded protein response to plant defense suppression by Ustilago maydis

“…RNAseq analysis revealed that factors previously shown to be important for ER stress resistance in U . maydis or other fungi such as the co-chaperone Dnj1 (UMAG_05173) [49], the protein disulfide isomerase Pdi1 (UMAG_10156) [48], the ER oxidoreductase Ero1 (UMAG_05219) [91] and the ER chaperones Lhs1 (UMAG_00904) [47] and Bip1 (UMAG_15034) [92], showed reduced expression levels during clp1 -modulated UPR. With the aim to identify novel factors for ER stress resistance and virulence, UPR core genes were chosen for gene deletion based on increased or unchanged expression levels during clp1 -modulated UPR.…”