SymB and SymC, two membrane associated proteins, are required for Epichloë festucae hyphal cell–cell fusion and maintenance of a mutualistic interaction with Lolium perenne

Abstract

SummaryCell-cell fusion in fungi is required for colony formation, nutrient transfer and signal transduction. Disruption of genes required for hyphal fusion in Epichlo€ e festucae, a mutualistic symbiont of Lolium grasses, severely disrupts the host interaction phenotype. They examined whether symB and symC, the E. festucae homologs of Podospora anserina selfsignaling genes IDC2 and IDC3, are required for E. festucae hyphal fusion and host symbiosis. Deletion mutants of these genes were defective in hyphal cell fusion, formed intra-hyphal hyphae, and had enhanced conidiation. SymB-GFP and SymC-mRFP1 localize to plasma membrane, septa and points of hyphal cell fusion. Plants infected with DsymB and DsymC strains were severely stunted. Hyphae of the mutants colonized vascular bundles, were more abundant than wild type in the intercellular spaces and formed intra-hyphal hyphae. Although these phenotypes are identical to those previously observed for cell wall integrity MAP kinase mutants no difference was observed in the basal level of MpkA phosphorylation or its cellular localization in the mutant backgrounds. Both genes contain binding sites for the transcription factor ProA. Collectively these results show that SymB and SymC are key components of a conserved signaling network for E. festucae to maintain a mutualistic symbiotic interaction within L. perenne.

Phosphatidic acid produced by phospholipase D is required for hyphal cell-cell fusion and fungal-plant symbiosis

“…The severe host interaction phenotype observed for the DpldB mutant was very similar to that reported previously for several other E. festucae symbiotic mutants (Tanaka et al, 2006, Tanaka et al, 2013, Eaton et al, 2010, Becker et al, 2015, Takemoto et al, 2006, Green et al, 2017. Instead of wild-type like restricted hyphal growth, the DpldB mutant had a proliferative pattern of growth in planta.…”

“…In addition to the hyphal fusion defect, the DpldB mutant was unable to form expressoria, appressorium-like structures that allow endophytic hyphae below the cuticle to swell up and penetrate this layer to emerge and grow on the surface of the leaf. Instead, the hyphae proliferate below the surface of the cuticle, a phenotype also observed for E. festucae nox complex, and some other symbiotic mutants that are defective in a conserved signaling network for cell fusion and multi-cellular development (Becker et al, 2016, Green et al, 2017, Green et al, 2019, Scott et al, 2018. Development of a functional appressorium in M. oryzae requires both Nox1 and Nox2 (Egan et al, 2007).…”

Disruption of calcineurin catalytic subunit (cnaA) in Epichloë festucae induces symbiotic defects and intrahyphal hyphae formation

“…The formation of intrahyphal hyphae is widespread in fungi, occurring in response to hyphal and/or cellular damage (Bowman et al, 2006;Calonge, 1968;Takeshita et al, 2006). Such structures have been observed previously in CWI MAP kinase, membrane-associated protein and component of striatininteracting phosphatase and kinase complex mutants of E. festucae; chitin synthase mutants of A. nidulans, Fusarium graminearum and Colletotrichum graminicola; and glycosylphosphatidylinositol synthesis gene mutants of N. crassa and C. graminicola (Becker et al, 2015;Bowman et al, 2006;Green et al, 2016Green et al, , 2017Horiuchi et al, 1999;Kim et al, 2009;Oliveira-Garcia and Deising, 2016;Werner et al, 2007). In A. fumigatus, intrahyphal hyphae formation was promoted by treatment with caspofungin, which inhibits b-1,3-glucan synthase (Walker et al, 2015).…”

“…crassa and C . graminicola (Becker et al ., ; Bowman et al ., ; Green et al ., ; Horiuchi et al ., ; Kim et al ., ; Oliveira‐Garcia and Deising, ; Werner et al ., ). In A .…”

Recent development of boronic acid-based fluorescent sensors

“…Starch and glycogen can serve as energy reserves to sustain life. In addition, they can combine with other molecules to form glycoproteins, glycolipids and so on, 29 which play key roles in many biological basic activities such as cancer migration, 30 cell fusion, 31 protein function regulation 32 and embryo development. 33 Consequently, the recognition of carbohydrates in the medical, cell biology and other life sciences is of great signicance.…”