Sclerotinia sclerotiorumγ-Glutamyl Transpeptidase (Ss-Ggt1) Is Required for Regulating Glutathione Accumulation and Development of Sclerotia and Compound Appressoria

Abstract

Transcripts encoding Sclerotinia sclerotiorum γ-glutamyl transpeptidase (Ss-Ggt1) were found to accumulate specifically during sclerotium, apothecium, and compound appressorium development in S. sclerotiorum. To determine the requirement of this protein in these developmental processes, gene deletion mutants of Ss-ggt1 were generated and five independent homokaryotic ΔSs-ggt1 mutants were characterized. All deletion mutants overproduced sclerotial initials that were arrested in further development or eventually produced sclerotia with aberrant rind layers. During incubation for carpogenic germination, these sclerotia decayed and failed to produce apothecia. Total glutathione accumulation was approximately 10-fold higher and H(2)O(2) hyperaccumulated in ΔSs-ggt1 sclerotia compared with the wild type. Production of compound appressoria was also negatively affected. On host plants, these mutants exhibited a defect in infection efficiency and a delay in initial symptom development unless the host tissue was wounded prior to inoculation. These results suggest that Ss-Ggt1 is the primary enzyme involved in glutathione recycling during these key developmental stages of the S. sclerotiorum life cycle but Ss-Ggt1 is not required for host colonization and symptom development. The accumulation of oxidized glutathione is hypothesized to negatively impact these developmental processes by disrupting the dynamic redox environment associated with multicellular development.

Changes in the Sclerotinia sclerotiorum transcriptome during infection of Brassica napus

“…The enzyme γ-glutamyl transpeptidase regulates glutathione levels and in turn cellular redox potential. In S. sclerotiorum , the γ-glutamyl transpeptidase encoded by SS1G_14127 (SsGgt1) plays a role in the production of compound appressoria during host penetration as well as in the development of sclerotia, but is not necessary for host colonization and symptom development [24]. In the current study, SS1G_14127 was up-regulated from 6-48 hpi, while genes encoding two other γ-glutamyl transpeptidases (SS1G_05530 and SS1G_10940) were up-regulated during the later stages at 24 and 48 hpi, respectively.…”

“…Both γ-glutamyl transpeptidase ( SsGgt1 ) and compound appressorium formation-related protein 1 (Ss - Caf1) influence the production of compound appressoria and subsequent host penetration, but also development of sclerotia [24, 25]. A secreted integrin-like protein (SSITL) inhibits the deployment of plant defenses through the jasmonic/ethylene signaling pathways [26] and a chorismate mutase ( SsCm1 ) may function similarly to suppress plant defense responses during the biotrophic phase [27].…”

Activation of transsulfuration pathway by salvianolic acid a treatment: a homocysteine-lowering approach with beneficial effects on redox homeostasis in high-fat diet-induced hyperlipidemic rats

“…Under oxidative stress conditions, ROS are reduced by GSH with concomitant formation of the GSSG [37]. However, GSSG did not accumulation in the setting of hyperlipidemia.…”

Disruption of the Gene Encoding Endo-β-1, 4-Xylanase Affects the Growth and Virulence of Sclerotinia sclerotiorum

“…Until now, many genes associated with cell signal transduction pathway have been confirmed to control this process in S. sclerotiorum (Jurick and Rollins, 2007; Li et al, 2012), but the proteins that worked downstream of the signal transduction pathway to control sclerotial germination have remained largely unknown. In this research, the sclerotia for SsXyl1 deletion mutants cannot germinate to form apothecia suggesting that SsXyl1 is related to the carpogenic germination.…”

“…Disruption of adenylate cyclase gene Sac1 in S. sclerotiorum decreases cAMP and impairs carpogenic germination of sclerotia suggesting that the cAMP signal pathway regulates the sclerotial germination (Jurick and Rollins, 2007). The process was also influenced by glutathione accumulation because the sclerotia produced by the strain that lost the gamma-glutamyl transpeptidase gene Ss-Ggt1 failed to produce apothecia (Li et al, 2012). Furthermore, some secreted proteins located at the cell wall were identified as being associated with the sclerotial germination of S. sclerotiorum (Zhu et al, 2013; Xiao et al, 2014).…”