A Novel Class of Ectomycorrhiza-Regulated Cell Wall Polypeptides in Pisolithus tinctorius

Abstract

Development of the ectomycorrhizal symbiosis leads to the aggregation of fungal hyphae to form the mantle. To identify cell surface proteins involved in this developmental step, changes in the biosynthesis of fungal cell wall proteins were examined in Eucalyptus globulus-Pisolithus tinctorius ectomycorrhizas by two-dimensional polyacrylamide gel electrophoresis. Enhanced synthesis of several immunologically related fungal 31- and 32-kDa polypeptides, so-called symbiosis-regulated acidic polypeptides (SRAPs), was observed. Peptide sequences of SRAP32d were obtained after trypsin digestion. These peptides were found in the predicted sequence of six closely related fungal cDNAs coding for ectomycorrhiza up-regulated transcripts. The PtSRAP32 cDNAs represented about 10% of the differentially expressed cDNAs in ectomycorrhiza and are predicted to encode alanine-rich proteins of 28.2 kDa. There are no sequence homologies between SRAPs and previously identified proteins, but they contain the Arg-Gly-Asp (RGD) motif found in cell-adhesion proteins. SRAPs were observed on the hyphal surface by immunoelectron microscopy. They were also found in the host cell wall when P. tinctorius attached to the root surface. RNA blot analysis showed that the steady-state level of PtSRAP32 transcripts exhibited a drastic up-regulation when fungal hyphae form the mantle. These results suggest that SRAPs may form part of a cell-cell adhesion system needed for aggregation of hyphae in ectomycorrhizas.

Signal and nutrient exchange at biotrophic plant–fungus interfaces

“…hydrophobins and symbiosis-regulated acidic polypeptides) were identified. These proteins are likely to be involved in cell-cell adhesion at the symbiotic interface [5][6][7]. Similarly, putative cell-wall proteins at the interface in the AM symbiosis between Glomus versiforme and M. truncatula have been characterized [8].…”

Genome-wide analysis of cell wall-related genes in Tuber melanosporum

“…In addition to the contact with host surface, the fungal cell wall of ECM fungi is involved in both the adhesion events that occur during the mantle formation and in the creation of the symbiotic interface between the Hartig net hyphae and the root cells . The involvement of cell wall components during ECM development has already been investigated (Balestrini et al 1996;Laurent et al 1999;Martin et al 1999; Tagu et al 2001). Taking advantage of the recently released genome sequence of the Tuber melanosporum black truffle (Martin et al 2010), we have obtained a genome-wide inventory of the proteins that are involved in cell wall synthesis and remodeling.…”

Profiling of differentially expressed genes in ectomycorrhizal fungus Pisolithus tinctorius responding to mycorrhiza helper Brevibacillus reuszeri MPt17

“…Three hypothetical symbiosis-related genes encoding symbiosis regulated acidic polypeptide (PtBrS008, PtBrS054 and PtBrS105) have been identified in the constructed SSH library. The symbiosis-regulated acidic polypeptides were first described by Laurent et al (1999) and named as SRAPs. They function as cell surface proteins involved in Eucalyptus globules-Pi.…”

“…tinctorius ectomycorrhiza interaction. SRAPs may form part of a cell-cell adhesion system needed for aggregation of hyphae in ectomycorrhizae (Laurent et al 1999). All of the 3 SRAPs in our study were up-regulated when Pi.…”