Discovered a new plant immunity mechanism sharing regulatory elements with the stomata developmental pathway

Researchers of the CBGP (UPM-INIA) belonging to the group of "Plant Innate immunity and resistance to necrotrophic fungi", led by Dr. Antonio Molina, have identified a new plant immune signalling pathway that upon constitutive activations able confers broad spectrum disease resistance to bacteria, fungi and oomycetes. This study, conducted in collaboration with several international research groups, was published in the New Phytologist journal and shows that plants have co-opted for this immune pathway part of the signalling components that regulate the formation of stomata, such as ERECTA (ER), a membrane kinase-type receptor, and YODA (YDA), a MAP3K-type protein kinase.

This new immunity pathway would act in parallel to the previously described immunity pathways that are regulated by Microbe-Associated Molecular Patterns (MAMPs) that are recognized by the plant's Pattern RecognitionReceptors (PRRs), and by the classic phytohormones, such as salicylic acid, ethylene or jasmonic acid. Stomata are natural openings of the plants that allow the gaseous exchange, but in turn act as points of entry of pathogenic microorganisms.

The discovery of this new route of plant immunity mediated by YDA and ER, the regulators of the formation of stomata, suggests that plants have been evolutionarily endowed with an immunity system linked to the development of stomata. The article shows that constitutive activation of the YDA (CA-YDA) protein confers long-lasting and broad-spectrum resistance. The CA-YDA plants present alterations in their cell walls and constitutively express defense-associated genes, such as those encoding putative small secreted peptides (SSPs), and membrane receptor proteins (PRRs).

These SSPs or glycans derived from CA-YDA cell walls could act as Damage-Associated Molecular (DAMPs), which once recognized by specific PRRs would activate the immune signalling mediated by ER-YDA. The characterization of this new immunity pathway would allow the development of crops with enhanced disease resistance.

Model of ER-YDA signaling pathway regulating plant immunity and development. The complex receptorsome, including ER paralogs (ERL1 and ERL2), the receptor like protein (RLP) TMM and somatic embryogenesis receptor kinases (SERKs, e.g. BAK1), required for ER-mediated stomatal patterning, is also involved in ER-mediated immunity. ER-YDA immune pathway is independent of the defensive responses activated by flg22 and chitin.

Original Paper:

Sopeña-Torres, S; Jordá, L; Sánchez-Rodríguez, C; Miedes, E; Escudero, V; Swami, S; López, G; Piślewska-Bednarek, M; Lassowskat, I; Lee, J; Gu, Y; Haigis, S; Alexander, D; Pattathil, S; Muñoz-Barrios, A; Bednarek, P; Somerville, S; Schulze-Lefert, P; Hahn, MG; Scheel, D; Molina, A. 2018. "YODA MAP3K kinase regulates plant immune responses conferring broad-spectrum disease resistance". New Phytologist. DOI: 10.1111/nph.15007".