Early Lotus japonicus root transcriptomic responses to symbiotic and pathogenic fungal exudates

Abstract

The objective of this study is to evaluate Lotus japonicus transcriptomic responses to arbuscular mycorrhizal (AM) germinated spore exudates (GSEs), responsible for activating nuclear Ca2+ spiking in plant root epidermis. A microarray experiment was performed comparing gene expression in Lotus rootlets treated with GSE or water after 24 and 48 h. The transcriptional pattern of selected genes that resulted to be regulated in the array was further evaluated upon different treatments and timings. In particular, Lotus rootlets were treated with: GSE from the pathogenic fungus Colletotrichum trifolii; short chitin oligomers (COs; acknowledged AM fungal signals) and long COs (as activators of pathogenic responses). This experimental set up has revealed that AM GSE generates a strong transcriptomic response in Lotus roots with an extensive defense-related response after 24 h and a subsequent down-regulation after 48 h. A similar subset of defense-related genes resulted to be up-regulated also upon treatment with C. trifolii GSE, although with an opposite trend. Surprisingly, long COs activated both defense-like and symbiosis-related genes. Among the genes regulated in the microarray, promoter-GUS assay showed that LjMATE1 activates in epidermal cells and root hairs.

Arbuscular mycorrhizal phenotyping: the dos and don'ts

“…Strong early phenotypes could be due to the plant's inability to either produce active compounds such as SLs to prime the fungi or to recognize fungal compounds such as LCOs or COs. To distinguish between these two scenarios, global transcriptomics of plant or AM fungi have been implemented to compare transcriptional responses to germinated spore exudates (GSEs) of the AM fungi or plant root exudates, respectively (Campos‐Soriano et al ., ; Giovannetti et al ., ; Gutjahr et al ., ; Nadal et al ., ). Alternatively, nurse plant experiments where mutants are co‐cultivated with wild‐type plants can be performed.…”

The Influence of Contrasting Microbial Lifestyles on the Pre-symbiotic Metabolite Responses of Eucalyptus grandis Roots

“…in comparison to pathogenic Pseudomonas bacteria (Kamilova et al, 2006). Distinctive transcriptomic responses to symbionts, as opposed to pathogens, have also been demonstrated at this early presymbiotic stage (Giovannetti et al, 2015). Plant responses may also vary between different isolates of the same microbial species whereby discrete modifications in plant responses to intra-specific microbial variation could correlate with improved compatibility in certain interactive pairs over others.…”

Lotus Base: An integrated information portal for the model legume Lotus japonicus

“…We have mapped probe identifiers from the LjGEA dataset against the annotated proteins of L. japonicus genome v3.0 by performing BLAST alignments of LjGEA probe set against the predicted transcripts from L. japonicus genome v3.0 and selecting for hits with the lowest E-value(s). In addition to the LjGEA dataset, we have also integrated expression data from Lotus roots in response to germinating spore exudates from arbuscular mycorrhiza5, containing 3 conditions.…”

“…Lotus japonicus is a popular, well-characterized model legume1, widely used to study plant-microbe interactions due to its ability to establish a range of different types of relationship with microorganisms along the symbiosis–pathogenesis spectrum—ranging from biological nitrogen fixation2 and arbuscular mycorrhizal symbiosis3, to bacterial4 and fungal5 pathogenesis. The establishment of the LORE1 mutant population678 and the annotated sequence of the Lotus japonicus genome9 necessitated a centralized and freely available online resource for researchers working with this model legume.…”