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A plant RNA-binding protein senses 2′,3′-cNMP produced by insect effectors
Nature
(2026) Cite this article
RNA-derived 2′,3′-cyclophosphate-terminated nucleotides act as immune signalling molecules in prokaryotes and eukaryotes1,2,3, but how plants perceive them remains unknown. Sucking insects inject digestive enzymes including RNases into the host plant to acquire nutrients. Here we demonstrate that NIB1, a glycine-rich RNA-binding protein in rice, senses 2′,3′-cyclic nucleotide monophosphates (2′,3′-cNMPs; 2′,3′-cAMP and 2′,3′-cGMP) and adenylyl-(3′→5′)-guanosine 2′,3′-cyclic phosphate (ApG>p) produced by a salivary T2 ribonuclease of green stink bug during feeding. Binding of the RNase products promotes formation of nuclear condensates containing NIB1, which recruit the core immune regulator Enhanced Disease Susceptibility 1 (EDS1) and activate defence, potentially contributing to the immune signalling of Toll/interleukin-1 receptor (TIR) proteins that also produce the nuclease products. Exogenous application of 2′,3′-cAMP, 2′,3′-cGMP or ApG>p elicits NIB1 and EDS1-mediated immune responses. Our findings unveil a conserved pathway in plants, in which glycine-rich RNA-binding proteins perceive the nuclease-generated second messengers to launch defence and point to a potential link between plant TIR nuclease activity and EDS1 signalling.
Insect pests cause losses to crop production and damage vegetation4,5. During feeding, insects release oral secretions containing proteins and other molecules that can activate or suppress host plant defence6,7,8. Digestive enzymes hydrolyse cellular components to generate nutrients for herbivores. These breakdown products also act as host-derived damage-associated molecular patterns (DAMPs) that activate plant pattern-recognition receptors9,10. Identifying host-derived signalling molecules and their defence activation mechanisms is essential for developing new plant-protection strategies.
T2-family ribonuclease (RNaseT2) proteins, which preferentially cleave single-strand RNAs between purine and uridine residues, are ancient enzymes that are widely distributed across organisms and functional in diverse biological processes2,11. Plant S-RNases, which mediate self-incompatibility, belong to this protein family12. Phytopathogens also secrete nucleases into host tissues13,14. Human lysosomal RNaseT2 generates purine-2′,3′-cyclophosphate-terminated oligoribonucleotides that are sensed by Toll-like receptor 8 to activate innate immunity2. Toll/interleukin-1 receptor (TIR) domains of plant intracellular nucleotide-binding and leucine-rich repeat (NLR) immune receptors possess enzymatic activities towards oxidized nicotinamide adenine dinucleotide (NAD+) and nucleic acids15,16,17,18,19. Plant TIR domains generate second messengers such as 2′-ADPR and pRib-AMP, which promote the formation of EDS1–Phytoalexin Deficient 4 (PAD4)–Activated Disease Resistance 1 (ADR1) complex and trigger disease resistance15,20,21. Activated plant TIR also catalyses the production of ADPr-ATP and di-ADPR, leading to the complex formation of EDS1-Senescence-Associated Gene 101 (SAG101)–N Required Gene 1 (NRG1), inducing plant cell death16,22,23. Plant TIR domains also synthesize 2′,3′-cAMP and 2′,3′-cGMP (2′,3′-cAMP/cGMP) through nuclease activity. Arabidopsis nudix hydrolase 7 (AtNUDT7) hydrolyses 2′,3′-cAMP/cGMP and attenuates TIR-mediated cell death when overexpressed in Nicotiana benthamiana3. However, the contribution of 2′,3′-cAMP/cGMP to EDS1-dependent immunity remains elusive.
Plant glycine-rich RNA-binding proteins (GRPs) encompassing one RNA recognition motif (RRM) at the N terminus and a glycine-rich region (GRR) at the C terminus regulate plant responses to abiotic and biotic stresses24,25. Arabidopsis GRP7 (AtGRP7) has a positive role in immunity, whereas the Pseudomonas syringae effector HopU1 suppresses AtGRP7-mediaed immunity by catalysing ADP-ribosylation of an arginine residue (R49) in the RRM of AtGRP726,27,28. These data indicate that the RRM