Detection of symbiosis‐related polypeptides during the early stages of the establishment of arbuscular mycorrhiza between Glomus mosseae and Pisum sativum roots

Abstract

SUMMARYChanges in polypeptide contents following inoculation of roots of Pisum sativum L. (wild type cv. Frisson (myc^, nod^)) with the arbuscular mycorrhizal fungus Glomus mosseae were analysed by two-dimensional gel electrophoresis (2D-PAGE). A different polypeptide pattern was obtained in a mycorrhiza-resistant pea genotype P2 (myc", nod") inoculated with G. mosseae. In order further to characterize the polypeptide modifications detected and to provide evidence for some possible symbiosis-related (SR) proteins, a time course experiment, from appressoria formation to fully developed symbiosis, was carried out on two genotypes allowing fungal colonization: the wild type and its isogenic mutant P56 (myc^, nod"). The same experiment was done with the mycorrhiza-resistant pea genotype (myc", nod"). After G. mosseae inoculation, we characterized 12 additional polypeptides in the two mycorrhiza-compatible pea genotypes which were never observed in root extracts from the mycorrhiza-resistant mutant. Five polypeptides were first detected in the early stage of the symbiosis (5 d of inoculation) while others were observed later (8 d of inoculation). The induction and accumulation of these polypeptides seem to be more correlated to the establishment of the functional symbiosis than to the recognition stages and appressorium formation. Furthermore, none of the additional polypeptides were detected in the mycorrhiza-resistant pea genotype. This mutant was more characterized by a great repression of polypeptides. In addition, up-regulated and down-regulated polypeptides from the mycorrhiza-compatible genotypes were different from those of the mycorrhiza-resistant genotype.

Soluble and membrane symbiosis‐related polypeptides associated with the development of arbuscular mycorrhizas in tomato (Lycopersicon esculentum)

“…These data confirm those reported in tobacco (Dumas-Gaudot et al, 1994) and pea (Samra et al, 1997). In Ri-T-DNA transformed tomato root the accumulation of two new acidic polypeptides of 24 and 39 kDa has been reported (Simoneau et al, 1994) during the development of mycorrhiza ; however, we have not been able to detect these polypeptides.…”

“…Our results concerning the effect of AM symbiosis on root gene expression, as with those reported by Dumas-Gaudot et al (1994) and Samra et al (1997), contrast with those obtained for ectomycorrhizas (Hilbert & Martin, 1988 ;Burgess et al, 1995). For the ectomycorrhizal associations studied, it has been shown that development of the symbiosis induced a massive decrease in the concentration of the proteins synthesized by the plant.…”

“…It has been hypothesized that the low molecular weight polypeptides, with an up-regulation, or de novo synthesis, might correspond to some known host defence proteins (Samra et al, 1997). This could be true for the soluble, but not for the membrane polypeptides because most of the defence reactions are located in the protoplasm and the cell wall.…”

“…However, an understanding of the molecular and genetic bases underlying the temporal and spatial control of genes involved in the development of the symbiosis is now within reach, as more advanced techniques of molecular and genetic analyses are being applied to mycorrhizal interactions. Electrophoretic analysis of total proteins extracted from mycorrhizal roots of different plant species have shown qualitative and quantitative changes in the protein patterns in comparison with non-mycorrhizal roots (Arines, Palma & Vilarin4 o, 1993 ;Simoneau et al, 1994 ;Dumas-Gaudot et al, 1994 ;Samra, Dumas-Gaudot & Gianinazzi, 1997). These studies have shown that mycorrhizal colonization of the root system results in the appearance of new proteins, increases the production of some polypeptides already present in uninfected roots and\or decreases the amount of others.…”

“…Up to now studies on the AM fungal polypeptides have been hampered by the fact that they are obligate symbionts with very limited capability for independent growth in the absence of the plant. Recently, some efforts have been made to identify symbiosisspecific polypeptides by using pea mutants unable to establish mycorrhizas (myc − ) (Samra et al, 1997) and by analysing the protein profiles of the spores of the AM fungus (Samra et al, 1996). Considering the fact that the polypeptide profile of the spores can differ substantially from that of the fungal mycelium, we have tried to analyse, by 2D-PAGE, the soluble and membrane fractions of the extraradical mycelium of G. mosseae, in order to detect specific endomycorrhizins in our system.…”