Table 1.

Identified DAMPs in plants.

Category	DAMP	Molecular structure or epitope	Source or precursor	Receptor or signaling regulator	Plant	References
Epidermis cuticle	Cutin monomers	C16 and C18 hydroxy and epoxy fatty acids	Epidermis cuticle	Unknown	Arabidopsis thaliana, Solanum lycopersicum	Fauth et al., 1998; Buxdorf et al., 2014
Cell wall polysaccharide fragments or degrading products	OGs	Polymers of 10–15 α-1-4-linked GalAs	Cell wall pectin	WAK1 (A. thaliana)	A. thaliana, G. max, N. tabacum	Norman et al., 1999; Bellincampi et al., 2000; Ferrari et al., 2007; Brutus et al., 2010; Galletti et al., 2011
	Cellooligomers	Polymers of 2-7 β-1,4-linked glucoses	Cell wall cellulose	Unknown	A. thaliana	Souza et al., 2017; Johnson et al., 2018
	Xyloglucan oligosaccharides	Polymers of β-1,4-linked glucose with xylose, galactose, and fructose side chains	Cell wall hemicellulose	Unknown	A. thaliana, Vitis vinifera	Claverie et al., 2018
	Methanol	Methanol	Cell wall pectin	Unknown	A. thaliana, Nicotiana tabacum	Dixit et al., 2013; Hann et al., 2014; Tran et al., 2018
Apoplastic peptides and proteins	CAPE1	11-aa peptide	Apoplastic PR1	Unknown	A. thaliana, S. lycopersicum	Chen et al., 2014
	GmSUBPEP	12-aa peptide	Apoplastic subtilase	Unknown	Glycine max	Pearce et al., 2010a
	GRIp	11-aa peptide	Cytosolic GRI	PRK5	A. thaliana	Wrzaczek et al., 2009, 2015
	Systemin	18-aa peptide (S. lycopersicum)	Cytosolic prosystemin	SYR1/2 (S. lycopersicum)	Some Solanaceae species	Pearce et al., 1991; Wang et al., 2018
	HypSys	15-, 18-, or 20-aa peptides	Apoplastic or cytoplasmic preproHypSys	Unknown	Some Solanaceae species	Pearce et al., 2001a; Pearce and Ryan, 2003; Pearce, 2011
	Peps	23∼36-aa peptides (A. thaliana)	Cytosolic and vacuolar PROPEPs	PEPR1/2 (A. thaliana)	A. thaliana, Zea mays, S. lycopersicum, Oryza sativa	Huffaker et al., 2006; Yamaguchi et al., 2006, 2010; Krol et al., 2010; Bartels et al., 2013; Hander et al., 2019
	PIP1/2	11-aa peptides	Apoplastic preproPIP1/2	RLK7	A. thaliana	Hou et al., 2014
	GmPep914/890	8-aa peptide	Apoplastic or cytoplasmic GmproPep914/890	Unknown	G. max	Yamaguchi et al., 2011
	Zip1	17-aa peptide	Apoplastic PROZIP1	Unknown	Z. mays	Ziemann et al., 2018
	IDL6p	11-aa peptide	Apoplastic or cytoplasmic IDL6 precursors	HEA/HSL2	A. thaliana	Wang X. et al., 2017
	RALFs	∼50-aa cysteine-rich peptides	Apoplastic or cytoplasmic RALF precursors	FER (A. thaliana)	A. thaliana, N. tabacum, S. lycopersicum	Haruta et al., 2014; Stegmann et al., 2017
	PSKs	5-aa peptides	Apoplastic or cytoplasmic PSK precursors	PSKR1/2 (A. thaliana)	A. thaliana, S. lycopersicum	Igarashi et al., 2012; Mosher et al., 2013; Zhang et al., 2018
	HMGB3	HMGB3 protein	Cytosolic and nuclear HMGB3	Unknown	A. thaliana	Choi H.W. et al., 2016
	Inceptin	11-aa peptide	Chloroplastic ATP synthase γ-subunit	Unknown	Vigna unguiculata	Schmelz et al., 2006
Extracellular nucleotides	eATP	ATP	Cytosolic ATP	DORN1/P2K1 (A. thaliana)	A. thaliana, N. tabacum	Chivasa et al., 2009; Choi et al., 2014a
	eNAD(P)	NAD(P)	Cytosolic NAD(P)	LecRK-I.8	A. thaliana	Wang C. et al., 2017
	eDNA	DNA fragments < 700 bp in length	Cytosolic and nuclear DNA	Unknown	Phaseolus vulgaris, P. lunatus, Pisum sativum, Z. mays	Wen et al., 2009; Duran-Flores and Heil, 2014, 2018; Barbero et al., 2016
Extracellular sugars	Extracellular sugars	Sucrose, glucose, fructose, maltose	Cytosolic sugars	RGS1 (A. thaliana)	A. thaliana, N. tabacum, Solanum tuberosum	Johnson and Ryan, 1990; Solfanelli et al., 2006; Guo et al., 2011; Bolouri Moghaddam and Van den Ende, 2012; Miao et al., 2013; Li et al., 2014
Extracellular amino acids and glutathione	Proteinogenic amino acids	Glutamate, cysteine, histidine, aspartic acid	Cytosolic amino acids	GLR3.3/3.6 or others (A. thaliana)	A. thaliana, S. lycopersicum, Oryza sativa	Qi et al., 2006; Li et al., 2013; Kadotani et al., 2016; Seo et al., 2016; Toyota et al., 2018
	Glutathione	Glutathione	Cytosolic glutathione	GLR3.3/3.6 (A. thaliana)	A. thaliana	Li et al., 2013