Symbiotic signalling is at the core of an endophyticFusarium solani-legume association

Abstract

38Legumes interact with a wide range of microbes in their root system, ranging from beneficial symbionts 39 to pathogens. Symbiotic rhizobia and arbuscular mycorrhizal glomeromycetes trigger a so-called 40 common symbiotic signalling pathway (CSSP), including the induction of nuclear calcium spiking in 41 the root epidermis. In our study, the recognition of an endophytic Fusarium solani strain K in Lotus 42 japonicus induced the expression of LysM receptors for chitin-based molecules, CSSP members and 43 CSSP-dependent genes in L. japonicus. In LysM and CSSP mutant/RNAi lines, root penetration and 44 fungal intraradical progression was either stimulated or limited while FsK exudates are perceived in a 45 CSSP-dependent manner, triggering nuclear calcium spiking in epidermal cells of Medicago truncatula 46Root Organ Cultures. Our results corroborate that the CSSP is a more common pathway than previously 47 envisaged, involved in the perception of signals from other microbes beyond the restricted group of 48 symbiotic interactions sensu stricto.

Unique and common traits in mycorrhizal symbioses

“…A few observations suggest a more general role, at least for individual CSSP members. In particular, L. japonicus CCamK and SymRK, or their orthologs in other species, were found to play a role in plant responses to beneficial microorganisms 84 , nematodes 85 , parasitic plants 86 , fungal endophytes 87 , pathogenic fungi 88 and thigmotropic stimuli 85,89 . These observations point to additional roles for individual CSSP members, in agreement with their presence in the genomes of charophytes, where their function has unfortunately not been characterized 20,58 .…”