Expression analysis of Clavata1-like and Nodulin21-like genes from Pinus sylvestris during ectomycorrhiza formation

The ecology and physiology of ectomycorrhizal (EcM) symbiosis with conifer trees are well documented. In comparison, however, very little is known about the molecular regulation of these associations. In an earlier study, we identified three EcM-regulated Pinus expressed sequence tags (EST), two of which were identified as homologous to the Medicago truncatula nodulin MtN21. The third EST was a homologue to the receptor-like kinase Clavata1. We have characterized the expression patterns of these genes and of auxin- and mycorrhiza-regulated genes after induction with indole-3-butyric acid in Pinus sylvestris and in a time course experiment during ectomycorrhizal initiation with the co-inoculation of 2,3,5-triiodobenzoic acid, an auxin transport inhibitor. Our results suggest that different P. sylvestris nodulin homologues are associated with diverse processes in the root. The results also suggest a potential role of the Clv1-like gene in lateral root initiation by the ectomycorrhizal fungus

Interactive and Single Effects of Ectomycorrhiza Formation and Bacillus cereus on Metallothionein MT1 Expression and Phytoextraction of Cd and Zn by Willows

Single and joint ectomycorrhizal (+ Hebeloma mesophaeum) and bacterial (+ Bacillus cereus) inoculations of willows (Salix viminalis) were investigated for their potential and mode of action in the promotion of cadmium (Cd) and zinc (Zn) phytoextraction. Dual fungal and bacterial inoculations promoted the biomass production of willows in contaminated soil. Single inoculations either had no effect on the plant growth or inhibited it. All inoculated willows showed increased concentrations of nutritional elements (N, P, K and Zn) and decreased concentrations of Cd in the shoots. The lowest biomass production and concentration of Cd in the willows (+ B. cereus) were combined with the strongest expression of metallothioneins. It seems that biotic stress from bacterial invasion increased the synthesis of these stress proteins, which responded in decreased Cd concentrations. Contents of Cd and Zn in the stems of willows were combination-specific, but were always increased in dual inoculated plants. In conclusion, single inoculations with former mycorrhiza-associated B. cereus strains decreased the phytoextraction efficiency of willows by causing biotic stress. However, their joint inoculation with an ectomycorrhizal fungus is a very promising method for promoting the phytoextraction of Cd and Zn through combined physiological effects on the plant

Inhibitory and physiological properties of 12 yeasts and bacteria antagonistic to Botrytis cinerea on strawberry fruits

Biological control of foliar and post-harvest diseases, Wageningen, NLD, 1992/11/29-1992/12/04International audienc

A novel class of ectomycorrhiza-regulated cell wall polypeptides in Pisolithus tinctorius

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 SRAP(32d) 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