Project description:Ectomycorrhizal fungi, such as Laccaria bicolor, support forest growth and sustainability by providing growth-limiting nutrients to their plant host through a mutualistic symbiotic relationship with host roots. We have previously shown that the effector protein MiSSP7 (Mycorrhiza-induced Small Secreted Protein 7) encoded by L. bicolor is necessary for the establishment of symbiosis with host trees, although the mechanistic reasoning behind this role was unknown. We demonstrate here that MiSSP7 interacts with the host protein PtJAZ6, a negative regulator of jasmonic acid (JA)-induced gene regulation in Populus. As with other characterized JASMONATE ZIM-DOMAIN (JAZ) proteins, PtJAZ6 interacts with PtCOI1 in the presence of the JA mimic coronatine, and PtJAZ6 is degraded in plant tissues after JA treatment. The association between MiSSP7 and PtJAZ6 is able to protect PtJAZ6 from this JA-induced degradation. Furthermore, MiSSP7 is able to block--or mitigate--the impact of JA on L. bicolor colonization of host roots. We show that the loss of MiSSP7 production by L. bicolor can be complemented by transgenically varying the transcription of PtJAZ6 or through inhibition of JA-induced gene regulation. We conclude that L. bicolor, in contrast to arbuscular mycorrhizal fungi and biotrophic pathogens, promotes mutualism by blocking JA action through the interaction of MiSSP7 with PtJAZ6.
Project description:Poplars can be harmed by poplar canker. Inoculation with mycorrhizal fungi can improve the resistance of poplars to canker, but the molecular mechanism is still unclear. In this study, an aseptic inoculation system of L. bicolor-P. trichocarpa-B. dothidea was constructed, and transcriptome analysis was performed to investigate regulation by L. bicolor of the expression of genes in the roots of P. trichocarpa during the onset of B. dothidea infection, and a total of 3022 differentially expressed genes (DEGs) were identified. Weighted correlation network analysis (WGCNA) was performed on these DEGs, and 661 genes' expressions were considered to be affected by inoculation with L. bicolor and B. dothidea. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses showed that these 661 DEGs were involved in multiple pathways such as signal transduction, reactive oxygen metabolism, and plant-pathogen interaction. Inoculation with L. bicolor changed the gene expression pattern of the roots, evidencing its involvement in the disease resistance response of P. trichocarpa. This research reveals the mechanism of L. bicolor in inducing resistance to canker of P. trichocarpa at the molecular level and provides a theoretical basis for the practical application of mycorrhizal fungi to improve plant disease resistance.
Project description:The Poplar transcriptome was analyzed in mycorrhizal root tips in contact with Laccaria bicolor for 2 weeks. During mycorrhization the roots were treated with either 250µm ACC, 10nM JA or 500µM SA and compared to untreated mycorrhiza or control roots without contact to L. bicolor. In addition the poplar mutants 35S::PttACO1 and 35S::Atetr1 were used
Project description:To investigate which genes are affected by MiSSP7, a secreted effector protein of Laccaria bicolor, we analyzed the transcriptomes of poplar roots incubated with MiSSP7 protein.
Project description:BackgroundAccurate structural annotation is important for prediction of function and required for in vitro approaches to characterize or validate the gene expression products. Despite significant efforts in the field, determination of the gene structure from genomic data alone is a challenging and inaccurate process. The ease of acquisition of transcriptomic sequence provides a direct route to identify expressed sequences and determine the correct gene structure.MethodologyWe developed methods to utilize RNA-seq data to correct errors in the structural annotation and extend the boundaries of current gene models using assembly approaches. The methods were validated with a transcriptomic data set derived from the fungus Laccaria bicolor, which develops a mycorrhizal symbiotic association with the roots of many tree species. Our analysis focused on the subset of 1501 gene models that are differentially expressed in the free living vs. mycorrhizal transcriptome and are expected to be important elements related to carbon metabolism, membrane permeability and transport, and intracellular signaling. Of the set of 1501 gene models, 1439 (96%) successfully generated modified gene models in which all error flags were successfully resolved and the sequences aligned to the genomic sequence. The remaining 4% (62 gene models) either had deviations from transcriptomic data that could not be spanned or generated sequence that did not align to genomic sequence. The outcome of this process is a set of high confidence gene models that can be reliably used for experimental characterization of protein function.Conclusions69% of expressed mycorrhizal JGI "best" gene models deviated from the transcript sequence derived by this method. The transcriptomic sequence enabled correction of a majority of the structural inconsistencies and resulted in a set of validated models for 96% of the mycorrhizal genes. The method described here can be applied to improve gene structural annotation in other species, provided that there is a sequenced genome and a set of gene models.
Project description:Despite the pivotal role of jasmonic acid in the outcome of plant-microorganism interactions, JA-signaling components in roots of perennial trees like western balsam poplar (Populus trichocarpa) are poorly characterized. Here we decipher the poplar-root JA-perception complex centered on PtJAZ6, a co-repressor of JA-signaling targeted by the effector protein MiSSP7 from the ectomycorrhizal basidiomycete Laccaria bicolor during symbiotic development. Through protein-protein interaction studies in yeast we determined the poplar root proteins interacting with PtJAZ6. Moreover, we assessed via yeast triple-hybrid how the mutualistic effector MiSSP7 reshapes the association between PtJAZ6 and its partner proteins. In the absence of the symbiotic effector, PtJAZ6 interacts with the transcription factors PtMYC2s and PtJAM1.1. In addition, PtJAZ6 interacts with it-self and with other Populus JAZ proteins. Finally, MiSSP7 strengthens the binding of PtJAZ6 to PtMYC2.1 and antagonizes PtJAZ6 homo-/heterodimerization. We conclude that a symbiotic effector secreted by a mutualistic fungus may promote the symbiotic interaction through altered dynamics of a JA-signaling-associated protein-protein interaction network, maintaining the repression of PtMYC2.1-regulated genes.