Mediation of plant–mycorrhizal interaction by a lectin receptor-like kinase J Labbé, W Muchero, O Czarnecki, J Wang, X Wang, AC Bryan, K Zheng, … Nature plants 5 (7), 676-680

Abstract

The molecular mechanisms underlying mycorrhizal symbioses, the most ubiquitous and impactful mutualistic plant–microbial interaction in nature, are largely unknown. Through genetic mapping, resequencing and molecular validation, we demonstrate that a G-type lectin receptor-like kinase (lecRLK) mediates the symbiotic interaction between Populus and the ectomycorrhizal fungus Laccaria bicolor. This finding uncovers an important molecular step in the establishment of symbiotic plant–fungal associations and provides a molecular target for engineering beneficial mycorrhizal relationships.

SlZRT2 encodes a ZIP family Zn transporter with dual localization in the ectomycorrhizal fungus Suillus luteusL Coninx, N Smisdom, A Kohler, N Arnauts, M Ameloot, F Rineau, … Frontiers in microbiology 10

Ectomycorrhizal (ECM) fungi are important root symbionts of trees, as they can have significant effects on the nutrient status of plants. In polluted environments, particular ECM fungi can protect their host tree from Zn toxicity by restricting the transfer of Zn while securing supply of essential nutrients. However, mechanisms and regulation of cellular Zn homeostasis in ECM fungi are largely unknown, and it remains unclear how ECM fungi affect the Zn status of their host plants. This study focuses on the characterization of a ZIP (Zrt/IrtT-like protein) transporter, SlZRT2, in the ECM fungus Suillus luteus, a common root symbiont of young pine trees. SlZRT2 is predicted to encode a plasma membrane-located Zn importer. Heterologous expression of SlZRT2 in yeast mutants with impaired Zn uptake resulted in a minor impact on cellular Zn accumulation and growth. The SlZRT2 gene product showed a dual localization and was detected at the plasma membrane and perinuclear region. S. luteus ZIP-family Zn uptake transporters did not show the potential to induce trehalase activity in yeast and to function as Zn sensors. In response to excess environmental Zn, gene expression analysis demonstrated a rapid but minor and transient decrease in SlZRT2 transcript level. In ECM root tips, the gene is upregulated. Whether this regulation is due to limited Zn availability at the fungal–plant interface or to developmental processes is unclear. Altogether, our results suggest a function for SlZRT2 in cellular Zn redistribution from the ER next to a putative role in Zn uptake in S. luteus.

Plant Glutathione Transferases: Diverse, Multi-Tasking Enzymes with Yet-to-Be Discovered Functions J Csiszár, A Hecker, NE Labrou, P Schröder, DE Riechers Frontiers in plant science 10, 1304

Comparative transcriptomics of Gymnosporangium spp. teliospores reveals a conserved genetic program at this specific stage of the rust fungal life cycle SQ Tao, B Cao, E Morin, YM Liang, S Duplessis BMC genomics 20 (1), 723

Abstract

Background

Gymnosporangium spp. are fungal plant pathogens causing rust disease and most of them are known to infect two different host plants (heteroecious) with four spore stages (demicyclic). In the present study, we sequenced the transcriptome of G. japonicum teliospores on its host plant Juniperus chinensis and we performed comparison to the transcriptomes of G. yamadae and G. asiaticum at the same life stage, that happens in the same host but on different organs.

Results

Functional annotation for the three Gymnosporangium species showed the expression of a conserved genetic program with the top abundant cellular categories corresponding to energy, translation and signal transduction processes, indicating that this life stage is particularly active. Moreover, the survey of predicted secretomes in the three Gymnosporangiumtranscriptomes revealed shared and specific genes encoding carbohydrate active enzymes and secreted proteins of unknown function that could represent candidate pathogenesis effectors. A transcript encoding a hemicellulase of the glycoside hydrolase 26 family, previously identified in other rust fungi, was particularly highly expressed suggesting a general role in rust fungi. The comparison between the transcriptomes of the three Gymnosporangium spp. and selected Pucciniales species in different taxonomical families allowed to identify lineage-specific protein families that may relate to the biology of teliospores in rust fungi. Among clustered gene families, 205, 200 and 152 proteins were specifically identified in G. japonicum, G. yamadaeand G. asiaticum, respectively, including candidate effectors expressed in teliospores.

Conclusions

This comprehensive comparative transcriptomics study of three Gymnosporangium spp. identified gene functions and metabolic pathways particularly expressed in teliospores, a stage of the life cycle that is mostly overlooked in rust fungi. Secreted protein encoding transcripts expressed in teliospores may reveal new candidate effectors related to pathogenesis. Although this spore stage is not involved in host plant infection but in the production of basidiospores infecting plants in the Amygdaloideae, we speculate that candidate effectors may be expressed as early as the teliospore stage for preparing further infection by basidiospores.

At the nexus of three kingdoms: the genome of the mycorrhizal fungus Gigaspora margaritaprovides insights into plant, endobacterial and fungal interactions F Venice, S Ghignone, A Salvioli di Fossalunga, J Amselem, M Novero, … Environmental Microbiology

Summary

As members of the plant microbiota, arbuscular mycorrhizal fungi (AMF, Glomeromycotina) symbiotically colonize plant roots. AMF also possess their own microbiota, hosting some uncultivable endobacteria. Ongoing research has revealed the genetics underlying plant responses to colonization by AMF, but the fungal side of the relationship remains in the dark. Here, we sequenced the genome of Gigaspora margarita, a member of the Gigasporaceae in an early diverging group of the Glomeromycotina. In contrast to other AMF, G. margarita may host distinct endobacterial populations and possesses the largest fungal genome so far annotated (773.104 Mbp), with more than 64% transposable elements. Other unique traits of the G. margaritagenome include the expansion of genes for inorganic phosphate metabolism, the presence of genes for production of secondary metabolites and a considerable number of potential horizontal gene transfer events. The sequencing of G. margarita genome reveals the importance of its immune system, shedding light on the evolutionary pathways that allowed early diverging fungi to interact with both plants and bacteria.