GLR-dependent calcium and electrical signals are not coupled to systemic, oxylipin-based wound-induced gene expression in Marchantia polymorpha

[EN] center dot In angiosperms, wound-derived signals travel through the vasculature to systemically activate defence responses throughout the plant. In Arabidopsis thaliana, activity of vasculature-specific Clade 3 glutamate receptor-like (GLR) channels is required for the transmission of electrical signals and cytosolic Ca2+ (Ca2+) waves from wounded leaves to distal tissues, triggering activation of oxylipin-dependent defences. center dot Whether nonvascular plants mount systemic responses upon wounding remains unknown. To explore the evolution of systemic defence responses, we investigated electrical and calcium signalling in the nonvascular plant Marchantia polymorpha.
center dot We found that electrical signals and Ca2+ waves are generated in response to mechanical wounding and propagated to nondamaged distal tissues in M. polymorpha. Functional analysis of MpGLR, the only GLR encoded in the genome of M. polymorpha, indicates that its activity is necessary for the systemic transmission of wound-induced electrical signals and Ca2+ waves, similar to vascular plants. However, spread of these signals is neither coupled to systemic accumulation of oxylipins nor to a transcriptional defence response in the distal tissues of wounded M. polymorpha plants.
center dot Our results suggest that lack of vasculature prevents translocation of additional signalling factors that, together with electrical signals and Ca2+ waves, contribute to systemic activation of defences in tracheophytes.