Reconstructing the evolutionary history of gypsy retrotransposons in the Périgord black truffle (Tuber melanosporum Vittad.) T Payen, C Murat, F Martin. Mycorrhiza, 1-11

Abstract

Truffles are ascomycete fungi belonging to genus Tuber, and they form ectomycorrhizal associations with trees and shrubs. Transposable elements constitute more than 50 % of the black Périgord truffle (Tuber melanosporum) genome, which are mainly class 1 gypsy retrotransposons, but their impact on its genome is unknown. The aims of this study are to investigate the diversity of gypsy retrotransposons in this species and their evolutionary history by analysing the reference genome and six resequenced genomes of different geographic accessions. Using the reverse transcriptase sequences, six different gypsy retrotransposon clades were identified. Tmt1 and Tmt6are the most abundant transposable elements, representing 14 and 13 % of the T. melanosporumgenome, respectively. Tmt6 showed a major burst of proliferation between 1 and 4 million years ago, but evidence of more recent transposition was observed. Except for Tmt2, the other clades tend to aggregate, and their mode of transposition excluded the master copy model. This suggests that each new copy has the same probability of transposing as other copies. This study provides a better view of the diversity and dynamic nature of gypsy retrotransposons in T. melanosporum. Even if the major gypsy retrotransposon bursts are old, some elements seem to have transposed recently, suggesting that they may continue to model the truffle genomes.

Genetic diversity and genetic structure of black alder (Alnus glutinosa [L.] Gaertn) in the Belgium-Luxembourg-France cross-border area

Dominique Mingeot , Claude Husson, Patrick Mertens, Bernard Watillon, Pierre Bertin, Philippe Druart. Tree Genomics and Genomes

Impact of Phanerochaete chrysosporium on the Functional Diversity of Bacterial Communities Associated with Decaying Wood Hervé Vincent, Ketter Elodie, Pierrat Jean-Claude, Gelhaye Eric, Frey-Klett Pascale. PLoS ONE 1 (11), e0147100

Abstract

The poplar Rust-Induced Secreted Protein (RISP) inhibits the growth of the leaf rust pathogen Melampsora larici-populina and triggers cell culture alkalinisation B Petre, A Hecker, H Germain, P Tsan, J Sklenar, G Pelletier, A Séguin, … Frontiers in Plant Science 7, 97

Abstract

Plant cells secrete a wide range of proteins in extracellular spaces in response to pathogen attack. The poplar Rust-Induced Secreted Protein (RISP) is a small cationic protein of unknown function that was identified as the most induced gene in poplar leaves during immune responses to the leaf rust pathogen Melampsora larici-populina, an obligate biotrophic parasite. Here, we combined in planta and in vitro molecular biology approaches to tackle the function of RISP. Using a RISP-mCherry fusion transiently expressed in Nicotiana benthamiana leaves, we demonstrated that RISP is secreted into the apoplast. A recombinant RISP specifically binds to M. larici-populina urediniospores and inhibits their germination. It also arrests the growth of the fungus in vitro and on poplar leaves. Interestingly, RISP also triggers poplar cell culture alkalinisation and is cleaved at the C-terminus by a plant-encoded mechanism. Altogether our results indicate that RISP is an antifungal protein that has the ability to trigger cellular responses.

A new book of the series:  “Methods in Molecular Biology ” (Volume 1399 2016) entitled “MetaMicrobial Environmental Genomics” has been edited by F. Martin and S. Uroz

One chapter entitled :”Identification and in situ Distribution of a Fungal Gene Marker: The Mating Type Genes of the Black Truffle” has been written by H. De la Varga and C. Murat

Temporal changes of bacterial communities in the Tuber melanosporum ectomycorrhizosphere during ascocarp development. A Deveau, S Antony-Babu, F Le Tacon, C Robin, P Frey-Klett, S Uroz. Mycorrhiza, 1-11

Abstract

Ectomycorrhizae create a multitrophic ecosystem formed by the association between tree roots, mycelium of the ectomycorrhizal fungus, and a complex microbiome. Despite their importance in the host tree’s physiology and in the functioning of the ectomycorrhizal symbiosis, detailed studies on ectomycorrhiza-associated bacterial community composition and their temporal dynamics are rare. Our objective was to investigate the composition and dynamics of Tuber melanosporumectomycorrhiza-associated bacterial communities from summer to winter seasons in a Corylus avellana tree plantation. We used 16S ribosomal RNA (rRNA)-based pyrosequencing to compare the bacterial community structure and the richness in T. melanosporum’s ectomycorrhizae with those of the bulk soil. The T. melanosporum ectomycorrhizae harbored distinct bacterial communities from those of the bulk soil, with an enrichment in Alpha- and Gamma-proteobacteria. In contrast to the bacterial communities of truffle ascocarps that vastly varies in composition and richness during the maturation of the fruiting body and to those from the bulk soil, T. melanosporum ectomycorrhiza-associated bacterial community composition stayed rather stable from September to January. Our results fit with a recent finding from the same experimental site at the same period that a continuous supply of carbohydrates and nitrogen occurs from ectomycorrhizae to the fruiting bodies during the maturation of the ascocarps. We propose that this creates a stable niche in the ectomycorrhizosphere although the phenology of the tree changes.

The redox control of photorespiration: from biochemical and physiological aspects to biotechnological considerations. O Keech, P Gardeström, LA Kleczkowski, N Rouhier. Plant, Cell & Environment